Emergency Electrocardiographic Assessment of QRS-T Angle and N-Wave for Detecting NSTEMI with Left Circumflex Artery Stenosis

Emergency Electrocardiographic Assessment of QRS-T Angle and N-Wave for Detecting NSTEMI with Left Circumflex Artery Stenosis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Emergency Electrocardiographic Assessment of QRS-T Angle and N-Wave for Detecting NSTEMI with Left Circumflex Artery Stenosis Evren Dal, Suna ERAYBAR This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9169067/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background Early identification of left circumflex artery (LCX) stenosis in patients with non-ST-segment elevation myocardial infarction (NSTEMI) is challenging due to often non-diagnostic electrocardiographic (ECG) findings. This study evaluated the diagnostic value of the frontal QRS-T angle and N-wave presence on admission ECG for detecting LCX stenosis. Methods This retrospective study included 253 NSTEMI patients admitted between May 2022 and May 2023. All patients underwent coronary angiography, with ≥ 70% stenosis defined as significant. The frontal QRS-T angle was obtained from automated ECG reports, and N waves were assessed manually. Statistical analyses included group comparisons and receiver operating characteristic (ROC) analysis to determine the discriminatory ability of QRS-T angle for LCX involvement. Results LCX stenosis was present in 69.2% of patients, with 47.4% showing significant stenosis. The QRS-T angle was significantly higher in patients with multivessel disease (p = 0.004) and proximal LCX involvement (p = 0.012), but not associated with stenosis severity (p = 0.122). ROC analysis demonstrated modest discrimination for LCX involvement (AUC = 0.586, p = 0.039), with a cut-off of 100° yielding 35.92% sensitivity and 84.13% specificity. N-wave presence showed no significant association with LCX stenosis or QRS-T angle (p > 0.05). Conclusions The frontal QRS-T angle provide supportive diagnostic information for LCX involvement in NSTEMI, particularly in proximal lesions, but has limited ability to predict stenosis severity. N-wave presence was not a reliable indicator. The QRS-T angle serve as an adjunct ECG marker when interpreted alongside clinical and biochemical findings. Acute coronary syndrome NSTEMI QRS-T angle N wave fragmented QRS LCX stenosis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. INTRODUCTION Overcrowding in the emergency department is a worldwide problem associated with prolonged hospitalization, poor patient prognosis, and high costs. In early recognition of the critical patient, critical clues guiding assessment in diagnostic processes can be decisive. According to current guidelines, NSTEMI is diagnosed in approximately 10% of patients transferred to emergency departments for chest pain and this rate is gradually increasing [ 1 , 2 ]. Patients with NSTEMI with positive biomarkers constitute a high-risk group that is predicted to benefit from invasive treatment and antithrombotic [ 3 , 4 ]. For patients exhibiting at least one high-risk criterion, an early invasive strategy within 24 hours is advisable. These criteria include a confirmed diagnosis of NSTEMI based on the current guidelines, dynamic changes in ST-segment or T waves, transient ST-segment elevation, or a GRACE risk score greater than 140. (1). The diagnosis and initial short-term risk assessment of acute coronary syndromes should be grounded on a combination of factors, including the patient's clinical history, presenting symptoms, vital signs, physical examination findings, ECG results, and hs-cTn levels. Although coronary artery stenosis represents the most common mechanism underlying myocardial infarction, myocardial injury also occur due to alternative mechanisms such as coronary vasospasm, microvascular dysfunction, or supply–demand mismatch. However, the present study specifically focused on NSTEMI patients with angiographically evaluated coronary arteries in order to investigate the relationship between electrocardiographic parameters and LCX stenosis. Correct management of the diagnostic process of patients presenting with NSTEMI in the emergency department and recognizing very high-risk characteristics to identify which patient will undergo emergency angiography is essential. Analysis and management of the critical patient enable the early intensive care support or needed treatment regimen. The analysis and management of critical patients allow for the timely provision of intensive care support or the necessary treatment regimen. The lack of clear findings in NSTMI that point towards ischemia and the expectation of ischemia with the current findings delay the diagnostic process in the emergency department. For this purpose, research on the efficacy of NSTEMI findings, especially those evaluated at the time of initial presentation, in the diagnosis of NSTEMI continues in the literature. [ 5 – 8 ]. The STEMI-NSTEMI paradigm is based on the observation that ST elevation on the electrocardiogram in most MI patients is related to acute occlusion of the infarct-related artery. Unstable angina represents another component of the acute coronary syndrome spectrum; however, because it is not associated with detectable myocardial necrosis or biomarker elevation, these patients were not included in the present study, which specifically focused on NSTEMI cases with positive troponin levels. Subtotal stenosis often cause ST segment depression and negative T waves on the ECG. The prognosis following acute myocardial infarction is related to the localization of the infarction, the responsible coronary artery, and the level of stenosis of the coronary artery [ 9 ]. It is predicted that LCX artery stenosis are responsible for 20% of MIs. LCX involvement is underrecognized in patients presenting with acute coronary syndromes, particularly when classical ST-segment elevation patterns are absent on the standard 12-lead ECG. In such cases, the diagnosis is not based on ECG alone but on the integration of clinical presentation, cardiac biomarkers (troponins), and ECG findings, consistent with the inclusion criteria defined in the Materials and Methods section. When LCX involvement is suspected, additional posterior ECG leads provide complementary diagnostic information.. These patients are more likely to undergo percutaneous coronary intervention more than 24 hours following the onset of symptoms compared with patients with more easily recognizable left anterior descending (LAD) and right coronary artery (RCA) stenosis [ 10 , 11 ]. LCX occlusion should be considered in clinical pictures consistent with ACS despite non-diagnostic ECG findings. ST segment elevation exists in less than half of patients with LCX occlusion. ST segment elevation in D1 and AVL derivations or isoelectricity of the ST segment is common in patients with inferior myocardial infarction due to LCX stenosis. In addition, maximum ST segment depression in V2 or V3, seen in precordial derivations, has been found to have a specificity of 96% and a sensitivity of 70% for LCX stenosis [ 12 ]. The absence of ST segment depression or even ST segment elevation in AVL shows LCX stenosis. In the literature, the number of data showing the frequency and amount of ST segment and T wave changes on ECG due to isolated acute stenosis of LCX and their relationship with the level of stenosis is limited. In addition, in cases in which the left main coronary artery, left anterior descending artery (LAD), intermediate artery, right coronary artery, and their major branches are normal or no significant stenosis is found coronary angiographically, there is no adequate data indicating the presence, shape, and frequency of ST segment and T wave changes that develop in inferior, posterior and anterior derivations on ECG due to stenosis of the LCX alone [ 13 ]. ECG has long been a hot topic for researchers in the identification of the responsible coronary artery, prediction of the level of artery stenosis, and prognosis of patients with NSTEMI. Fragmented QRS (fQRS) is a new depolarization abnormality defined by Das et al. in 2006 as the presence of an additional R wave (R') or the presence of notching at the end of the R or S wave or the presence of more than one R' in 2 consecutive derivations corresponding to the supply territory of a major coronary artery [ 14 ]. Niu et al. interpreted the appearance of a notch in the terminal part of the QRS in DII; III, AVF or DI AVL as N wave in acute NSTEMI in the presence of the responsible lesion circumflex artery (LCX) and found it significant with a sensitivity of 77% and a specificity of 96% in circumflex artery lesions. The role of the N wave and whether this wave can be considered as an ST segment are not clear [ 15 , 16 ]. QRS-T angle, a new marker of ventricular repolarization heterogeneity, is defined as the angle difference between the direction of ventricular depolarization (QRS wave) and the direction of ventricular repolarization (T wave). The QRS-T angle in the frontal plane can be easily measured from the automatic report section of ECG devices and shows a good correlation with the spatial QRS-T angle in risk prediction. Studies have demonstrated the prognostic value of f(QRS-T) angle in different populations. It has been shown that a wide f(QRS-T) angle (> 90°) is a good predictor of long-term mortality in patients with left ventricular systolic dysfunction after acute myocardial infarction [ 17 – 19 ]. This change, which occurs as a result of impaired ventricular depolarization and repolarization, indicate an ischemic area and predict a significant change to indicate the responsible lesion. Seeing important clues in patients evaluated in the emergency department with chest pain and suspected acute coronary syndrome in the etiology make important contributions to patient management. Particularly in cases of acute coronary syndrome without ST segment elevation, obtaining information about stenosis localization and recognizing the critical patient can shorten serial troponin monitoring and emergency department follow-up time. Predicting the need for coronary angiography or intensive care with the ECG taken at the time of admission can have positive effects on survival. At this point, the evaluation of the QRS-T angle, which is often left out in routine use, and the N wave, which is a form of QRS fragmentation, can provide important information as an additional ECG finding in deciding the severity of patients, early consultation, or imaging decisions for patients. Previous studies investigating ECG predictors of LCX stenosis have been mainly conducted in cardiology settings and often focused on single parameters such as the N-wave or QRS-T angle. In contrast, our study evaluates both parameters simultaneously in NSTEMI patients at the point of emergency admission, aiming to determine their early diagnostic contribution before invasive procedures. This study aims to evaluate the relationship between acute stenosis of isolated LCX on admission ECG and the presence of QRS-T angle and N wave, which are measures reflecting ventricular repolarization and depolarization on ECG, and to examine their role in determining the level of stenosis in patients with NSTEMI. 2. METHODS 2.1 Patient Selection Patients who presented with ischemic chest pain or angina equivalent symptoms in the emergency department of our hospital in the 1-year period between May 1, 2022 and May 1, 2023, and who were diagnosed with NSTEMI as a result of cardiology consultation with positive serial troponin monitoring and were hospitalized in coronary intensive care unit were retrospectively evaluated. Written permission was obtained from the ethics committee of our hospital during the study planning phase (2019-KAEK-140 2023-11/8). Patients with ST segment elevation on emergency admission ECG, history of previous MI or coronary artery bypass (CABG) and patients whose ECG data were not available were excluded. Patients with prior myocardial infarction or CABG were excluded to avoid chronic repolarization abnormalities on ECG that could interfere with the assessment of acute ischemic finding.J point was used to determine the amount of ST change and pathologic Q wave, "ST elevation" and "ST depression" were determined according to the criteria specified in ESC/ACC [ 1 ]. Age, gender, comorbidities, emergency department presentation symptoms, and pain characteristics of the patients were recorded. Medical histories, including previously known diagnoses such as coronary artery disease, hypertension, diabetes mellitus, and heart failure, were reviewed from hospital records. The length of stay in the emergency department and the time until angiography were calculated. All included patients underwent coronary angiography according to current NSTEMI management guidelines after cardiology consultation, based on elevated cardiac troponin levels and supportive ischemic ECG findings 2.2 Coronary Angiography results The results of the investigations and the pathologies and interventions detected by coronary angiography were recorded on the patient files registered in the hospital automation system. Coronary angiography was performed by the interventional cardiology team as part of routine clinical care. The angiographic reports were retrospectively reviewed by the authors, and the severity of stenosis was determined according to the cardiologists’ visual assessment. Lesions with ≥ 70% luminal narrowing were considered significant. In this study, the term “stenosis” refers to partial luminal narrowing, whereas “occlusion” was used to describe complete (100%) obstruction of the coronary artery. Initially, patients with total occlusion or critical stenosis in LCX but with completely normal or less than 70% lesions in other coronary arteries were included in the evaluation. The stenosis in the LCX was classified according to its location as central (proximal segment, obtuse marginal branch, and intermediate branch) and peripheral (atrial branch, peripheral distal segment, posterolateral branch (Omi 2), and posterior descending branch). 2.3 Electrocardiographic measurements Electrocardiographic measurements were performed on the standard 12-leads ECG and, if available, on the posterior ECG recordings obtained at emergency department admission just before coronary angiography was performed. The QRS-T angle in the frontal plane was recorded from the automatic report section of the ECG devices and calculated automatically. The frontal QRS-T angle was considered as the difference between the frontal plane QRS axis and the T axis (Figure:1). If such a difference exceeded 180°, the frontal QRS-T angle was calculated as 360° minus the absolute value of the difference between the frontal plane QRS axis and the T axis (Figure:2). The N wave was defined as the appearance of a notch in the terminal part of the QRS in DII; III, AVF or DI AVL. (Figure: 3). ECGs were manually reviewed by the responsible investigators, blinded to the angiographic findings. Final confirmation was made by consensus between authors. 2.4 Statistical Analysis Statistical analyses were conducted in Jamovi 2.3.28 package program. While descriptive statistics of the qualitative variables in the study were presented with frequency and percentage, quantitative variables were given with mean, standard deviation, median, and minimum and maximum values. The conformity of quantitative variables to normal distribution was examined by the Shapiro-Wilk test. Independent sample t-test and Mann Whitney U test were used for independent 2-group comparisons of quantitative variables. The discrimination of the QRS-T variable according to LCX involvement and N wave was analyzed by ROC analysis. The relationships between quantitative variables were analyzed with the Pearson correlation coefficient. In all statistical analyses in the study, results with a p-value below 0.05 were considered statistically significant. 3. RESULTS 3.1 Patient Demographics and Baseline Characteristics A total of 490 patient data were retrospectively reviewed within the scope of our study. 210 patients were excluded due to STEMI detection, and 27 patients were excluded due to inaccessible study data. A total of 253 patients were included in the study. The inclusion status of patients is summarized in the study flow chart (Figure:4). The median age was 63 years (min: 34, max: 86), and 70% (n: 177) were male. Regarding chronic diseases, hypertension was the most common, affecting 74.4% (n: 189) of patients, followed by coronary artery disease (42.3%, n: 107) and diabetes mellitus (21.3%, n: 54). Chronic renal failure was present in 6.7% (n: 17), but no history of dialysis was recorded. Chest pain was recorded as typical ischemic chest pain in 66% of patients, with sweating and new-onset dyspnea considered as angina equivalent in 13.4% (n: 34). Patient characteristic’s summarized in Table 1 . Table 1 Patient Characteristics and Clinical Data Variable Category n % Gender Female 76 30.0 Male 177 70.0 Stent Presence Absent 220 87.0 Present 33 13.0 Diabetes Mellitus No 199 78.7 Yes 54 21.3 Hypertension (HT) No 64 25.3 Yes 189 74.7 Known Coronary Artery Disease history No 146 57.7 Yes 107 42.3 Chronic Renal Failure (CRF) No 236 93.3 Yes 17 6.7 Heart Failure (HF) No 220 87.0 Yes 33 13.0 Asthma No 253 100.0 Yes 0 0 Malignancy No 253 100.0 Yes 0 0 Chest Pain Characteristics None 34 13.4 Typical 167 66.0 Atypical 52 20.6 Additional symptoms Dyspnea 32 12.6 Nausea/Vomiting 13 5.1 Sweating 18 7.1 Fatigue 21 8.3 Epigastric Pain 12 4.8 3.2 Clinical and Angiographic Findings The median door-to-balloon time between emergency department evaluation and coronary angiography was 478 minutes. According to coronary angiography, 77.1% (n: 195) of patients had multivessel stenosis, 69.2% (n: 175) had circumflex artery stenosis, and 47.4% (n: 120) had stenosis > 70%. (Table 2 ). Table 2 Procedural Characteristics and Angiographic Results Angiographic Result Category n % LAD Occlusion None 70% 23 45 136 11.3 22.1 66.7 RCA Occlusion None 70% 62 59 83 30.4 40.7 30.8 LCX Occlusion None 70% 78 55 120 30,8 21.7 47.4 3.3 QRS-T Angle and Vessel Involvement Analysis of QRS-T values showed a significant difference between groups based on vessel involvement (p = 0.004). The QRS-T values were significantly higher in the multivessel group. However, no statistically significant difference was found between the percentage of LCX stenosis and the QRS-T angle (Table 3). Table-3 Vessel involvement and QRS-T angle value Angiographic vessel involvement p Single Vessel Multi Vessel QRS-T angle 51.51 ± 47.26 33 (− 189) 81.19 ± 62.94 64 (1–255) 0,004 a LCX Stenosis p 70.Stenosis QRS-T angle 63.16 ± 45.98 52 (2–158) 89.49 ± 69.83 65 (1–255) 0.122 a Mann Whitney U test 3.4 Impact of Proximal LCX Involvement on QRS-T Angle When analyzing the change in QRS-T angle values with respect to LCX involvement site, a statistically significant difference was observed in QRS-T between patients with and without involvement in the proximal segment (p = 0.012). QRS-T values were higher in patients with proximal segment involvement (Table 4). Table-4 QRS-T angle value and LCX involvement site QRS-T p Proximal segment No (n = 140) 65,66 ± 52,03 55 (1–221) 0,012 a Yes (n = 64) 95,84 ± 73,17 78 (1–255) Obtus marginalis No (n = 174) 73,69 ± 59,66 59,5 (1–255) 0,807 a Yes (n = 31) 80,84 ± 67,80 62 (1–245) Intermediate branch No (n = 150) 70,15 ± 58,07 56 (1–244) 0,105 a Yes (n = 55) 87,38 ± 66,74 69 (2–255) Atrial branch No (n = 197) 74,21 ± 61,21 59 (1–255) 0,348 a Yes (n = 8) 88,50 ± 52,11 84,5 (1–158) Peripheral distal segment No (n = 164) 73,31 ± 61,55 57 (1–255) 0,306 a Yes (n = 41) 80,63 ± 58,25 65 (6–249) Posterolateral branch No (n = 185) 74,64 ± 61,75 61 (1–255) 0,769 a Yes (n = 20) 76,00 ± 53,05 55 (3–151) Posterior descending branch No (n = 203) 74,09 ± 59,84 60 (1–255) - Yes (n = 2) - a Mann Whitney U test; \(\:\stackrel{-}{x}\) ±s; median (min – max) 3.5 Sensitivity and Specificity of QRS-T for LCX Involvement Regarding the discriminatory power of QRS-T for LCX involvement, ROC analysis showed significant discrimination with a sensitivity of 35.92% and specificity of 84.13% for a QRS-T value of 100 (AUC = 0.586; p = 0.039) (Figure:5) 3.6 N Wave Analysis and Correlation with Vessel Pathology The presence of N waves was detected in 46 (22.5%) ECGs. No statistically significant difference was found between the presence of N waves and multivessel involvement in coronary angiography (p = 0.469). Similarly, no significant relationship was observed between N waves and QRS-T values (p = 0.141) (Table 5). Additionally, there was no significant correlation between N wave presence and CX stenosis status, percentage, or regions (p > 0.05) (Table 6). Table-5 Relation of N wave and vessel involvement and QRS-T angle Angiographic vessel involvement p Single Vessel Multi Vessel N wave No 3 (%) 34 (%) 0.469 a Yes 1 (%) 7 (%) N wave No Yes p QRS-T 71.23 ± 58.59 55 (1–244) 87.70 ± 67.51 73 (2–255) 0.141 b a Yates chi-square test, b Mann Whitney U test Table-6 Relation of vascular stenosis percentage and N wave N wave p No Yes LAD Stenosis No 19 (%12.0) 4 (%8.7) 0.716 a Single vessel 139 (%88.0) 42 (%91.3) LAD Stenosis % 70% 108 (%77.7) 28 (%66.7) RCA Stenosis No 48 (%30.4) 14 (%30.4) 1.000 a Single vessel 110 (%69.6) 32 (%69.6) RCA Stenosis % 70% 61 (%55.5) 22 (%68.7) a Yates chi-square test 3.7 Correlation of QRS-T Angle with Troponin Levels A very weak positive correlation was observed between troponin values and QRS-T angle value. However, no significant correlation was found for LCX involvement specific to the affected vasculature, independent of the level of involvement (Table 7 ). When the effect of the presence of N waves on the change in QRS-T angle value and troponin levels was analyzed, a weak positive correlation was found between QRS-T and troponin values in patients without N waves, but no significant correlation was observed in patients with N waves. Table 7 QRS-T angle value differences due to LCX stenosis degree and N wave General Troponin-1 Troponin-2 Troponin-3 QRS-T r = 0,171 p = 0,014 r = 0,167 p = 0,017 r = 0,203 p = 0,006 LCX 70% QRS-T r = 0,101 p = 0,322 r = 0,161 p = 0,114 r = 0,137 p = 0,195 N wave negativity QRS-T r = 0,162 p = 0,042 r = 0,166 p = 0,037 r = 0,232 p = 0,005 N wave positivity QRS-T r = 0,168 p = 0,264 r = 0,202 p = 0,183 r = 0,227 p = 0,177 r: Pearson correlation coefficient 4. DISCUSSION Despite advances in the treatment of cardiovascular diseases, acute coronary syndromes remain a major cause of morbidity and mortality. ST-segment elevation alonenot always reflect ongoing ischemia, and it is no longer sufficient to focus on the presence or absence of ST-segment elevation as a reliable criterion to proceed with or postpone emergency angiography and/or reperfusion therapy. [ 20 , 21 ] Therefore, it is now important to recognize acute coronary syndrome without ST-segment elevation early and promptly refer to necessary reperfusion therapies. Hypertension (HT) and diabetes mellitus (DM) constitute an important part of the known risk factors for acute coronary syndrome [ 22 ]. The prevalence of HT and DM was found to be 84.6% and 29.0% higher in the elderly group compared to the non-elderly group, respectively [ 23 , 24 ]. Similar to the literature, HT was the chronic disease with the highest prevalence in our study, followed by coronary artery disease. Although the importance of managing the diagnostic process in the emergency department admission ECG in the presence of STEMI and taking the patient to percutaneous coronary intervention within 90 minutes is clearly stated in the literature, the optimal time in non-STEMI and USAP is changeable. For these patients, waiting in the emergency department for investigations or repeated enzyme monitoring prolongs the follow-up time. In addition, since the stenosis level of these patients cannot be clearly evaluated, there is no consensus on the required time. In our study, the median time to percutaneous intervention was 478 (min:1-max:17826) minutes. In cases with NSTEMI and USAP, there are studies showing that PCI was performed within 5 minutes at the earliest, 1440 minutes at the latest and 285.44 ± 265.79 minutes on average [ 25 ]. This temporal variation suggests that the decision was made based on the patient's clinic and complete stenosis was ignored. . In studies, among NSTEMI patients with LCX stenosis, those presenting with ST-segment depression were associated with larger infarct size and advanced acute heart failure than those without ST-segment changes [ 26 – 28 ]. Similar to the literature, in our study conducted in NSTEMI patients, a critical LCX lesion accompanying RCA stenosis was found in 47.4%. The QRS-T angle, a measurement from vector electrocardiography analysis, has been thoroughly researched since 1934 when Wilson and his team introduced the "ventricular gradient." This gradient, representing the combined spatial QRS-T angle, was believed to show the variability in action potential shapes, be mostly unaffected by the sequence of ventricular activation, and represent the "primary T-wave" or initial differences in repolarization. In contrast to the spatial ventricular gradient, the spatial QRS-T angle indicates a "secondary T-wave," which reflects repolarization abnormalities caused by depolarization issues, such as premature ventricular contractions, ventricular pacing, and bundle branch blocks, rather than primary differences in action potential shapes. Therefore, the QRS-T angle complements the ventricular gradient, and both can be used to evaluate patients with primary, secondary, or mixed repolarization abnormalities, like those found in left ventricular hypertrophy (LVH) (29). A wide QRS-T angle (≥ 90°), a marker of myocardial depolarization and repolarization as one of many electrocardiogram parameters, appears to be associated with electrical instability and has been associated with cardiac prognosis in several studies (29–31). In addition to traditional cardiac risk factors, QRS-T angle has been shown to contribute to the prediction of the risk of sudden cardiac death after ACS (e). Although studies have shown changes in the frontal QRS-T angle due to disturbances in coronary blood flow, it has not been found to be associated with the percentage of coronary involvement on coronary angiograms in NSTEMI patients. In our study, QRS-T angle was found to be significantly higher in multivessel involvement. ACS patients with ST-segment depression or without significant ST-segment changes are considered to have non-transmural infarction without vessel stenosis and usually do not undergo urgent coronary reperfusion. In this context, ACS with LCX stenosis often creates diagnostic problems and leads to late recognition of vessel stenosis. Diagnosis of acute LCX stenosis by standard 12-lead ECG is often difficult because more than half of acute LCX stenosis occur without characteristic ST-segment elevation on the ECG. When we looked at whether the QRS-T measurement was discriminative for LCX stenosis, the ROC analysis showed that it was significantly discriminative with 35.92% sensitivity and 84.13% specificity for QRS-T = 100 (AUC = 0.586; p = 0.039). Accordingly, evaluation of the frontal QRS-T angle on ECG, a simple and practical method, provide additional information for the early recognition of high-risk patients and assist in planning early revascularization strategies in clinical practice. In the evaluation of LCX lesion localization, it was observed that the QRS-T angle was determinative especially in LCX proximal segment stenosis, despite its insufficiency in showing the percentage of LCX stenosis. It is thought that proximal LCX lesions are frequently encountered in patients without ST segment depression or ST segment change [ 28 ]. The ST segment pattern and QRS-T angle should be interpreted carefully since large infarct areas caused by proximal LCX stenosis is present and result in cardiac failure in the advanced period. The lack of clear ECG findings in the diagnosis of NSTEMI has led many studies to identify new electrocardiographic indicators of coronary artery occlusion, such as the delayed activation wave or N-wave, which have been described as STEMI equivalents [ 15 ]. In our study, however, no significant relationship was observed between the presence of the N-wave and LCX stenosis. Previous reports by Niu et al. and Rostoff et al. demonstrated a strong association between the N-wave and circumflex lesions, but these studies included heterogeneous populations with unstable angina, multivessel involvement, and variable ischemic phases [ 6 , 15 ]. In contrast, our cohort consisted exclusively of patients with NSTEMI and angiographically isolated LCX stenosis, evaluated using ECGs obtained at emergency department admission. The discrepancy between our results and previous studies therefore reflect methodological and population differences, as well as variations in the definition and timing of N-wave assessment across studies. Although our study did not demonstrate a significant association between N wave and LCX stenosis, this finding contributes to the growing variability in the literature regarding the diagnostic meaning of this ECG pattern. Previous studies have reported different rates of N wave positivity depending on the population studied, the inclusion of anterior or inferior infarctions, and the definition thresholds applied. It is possible that N wave reflects a spectrum of ischemic and repolarization changes rather than a lesion-specific marker. In this context, our results support the view that N wave alone not indicate LCX-related ischemia but should be interpreted together with other ECG parameters and clinical findings in the emergency setting. Correct management of the diagnostic process of patients presenting with acute coronary syndrome in the emergency department is completed by detailed analysis of the admission ECG and interpretation of the repeated troponin test result. In the presence of NSTEMI, correct recognition of the patient and prolonging the follow-up period by making risk classifications are effective in the correct management of this process. The relationship between the QRS-T angle and troponin levels was examined at the point of interpreting troponin test results and ECG findings together. A weak correlation was found between the QRS-T angle value and troponin levels, which suggests that QRS-T angle should be evaluated as an early clue of the change in ventricular depolarization-repolarization cycle and myocardial necrosis. Additional studies are needed in this regard. Future multicenter prospective studies including larger patient populations and integrating additional electrocardiographic and imaging parameters provide a more comprehensive evaluation of the diagnostic value of the QRS-T angle in NSTEMI patients. 5. CONCLUSION The QRS-T angle reflects abnormalities in ventricular depolarization and repolarization that occur during myocardial ischemia. In the present study, an increased QRS-T angle was associated with the presence of LCX stenosis in patients with NSTEMI. However, this parameter appears to reflect ischemia-related electrical changes rather than the anatomical severity of coronary artery stenosis. These findings should be interpreted cautiously given the modest discriminatory performance observed in the ROC analysis (AUC = 0.586). Accordingly, although the QRS-T angle provide supportive electrocardiographic information suggesting LCX-related ischemia, it has limited ability to distinguish between different degrees of stenosis or to predict total occlusion. Left circumflex (LCX) occlusion or infarct-related artery stenosis results in a higher risk of major adverse cardiac events (MACE), delayed diagnosis, and inappropriately prolonged time to revascularization. Having important clues on the admission ECG in patients evaluated in the emergency department with chest pain and a suspected etiology of acute coronary syndrome can contribute to patient management and help in the early identification of Non STEMI patients. ST-segment changes on the 12-lead electrocardiogram can be used to distinguish between circumflex artery stenosis and right coronary artery stenosis. Knowing which vessel is occluded before percutaneous coronary intervention help in planning the procedure and in recognizing patients at high risk for conduction disturbances in the atrioventricular node. 6. LIMITATIONS The first limitation of our study is that it was a single-center and retrospective study. There was a loss of data due to the use of chart review. As a single-center retrospective study, our findings not be generalizable to different populations or healthcare settings, which limits the external validity of the results. The second limitation is that the percentages of stenosis detected in the angiographic results were evaluated and no comment could be made on the ischemic area and the responsible lesion. In-hospital outcomes, including complications, revascularization, or MACE, could not be evaluated due to incomplete inpatient data. In our study, the relationship between QRS-T angle and 28- and 90-day mortality could not be evaluated due to insufficient quantitative variables. The 90-day frequency of cardiac adverse events was also not evaluated due to lack of data. In addition, the effects of medications on ECG parameters and potential variations related to lead placement or patient body habitus could not be fully controlled, representing additional technical limitations of the study. Large-scale studies on this subject are needed. Abbreviations NSTEMI: Non-ST-segment elevation myocardial infarction LCX: Left circumflex artery ECG: Electrocardiogram ROC: Receiver operating characteristic AUC: Area under the curve Declarations There is no competing interest between authors. There is no financial and nonfinancial funding source to declare. Ethics approval and consent to participate This retrospective study was approved by the Ethics Committee of Bursa Sehir Training and Research Hospital, University of Health Sciences, Turkey (Approval No. 2019-KAEK-140 2023-11/8). The study was conducted in accordance with the principles of the Declaration of Helsinki . Due to the retrospective nature of the study and the use of anonymized patient data, informed consent to participate was waived by the Ethics Committee . Consent for publication Not applicable. Availability of data and materials The datasets generated and/or analyzed during the current study are not publicly available due to patient confidentiality but are available from the corresponding author on reasonable request. Competing Interests The authors declare that they have no competing interests. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Authors' contributions E.D. conceptualized the study, analyzed the data, and drafted the manuscript. S.E. contributed to data collection, interpretation, and critical revision of the manuscript. All authors read and approved the final manuscript. Acknowledgements The authors would like to thank the medical and administrative staff of Bursa Sehir Training and Research Hospital for their support during data collection. References Members WC, Gulati M, Levy PD, Mukherjee D, Amsterdam E, Bhatt DL, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain: a report of the American College of Cardiology/American Heart Association joint committee on clinical practice guidelines. J Am Coll Cardiol. 2021;78–e285. https://doi.org/10.1016/j.jacc.2021.07.053 . Collet JP, Thiele H, Barbato E, Barthelemy O, Bauersachs J, Bhatt DL, et al. 2020 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J. 2021;42:1289–367. https://doi.org/10.1093/eurheartj/ehaa575 . Kastrati A, Mehilli J, Neumann FJ, Dotzer F, ten Berg J, Bollwein H, et al. Abciximab in patients with acute coronary syndromes undergoing percutaneous coronary intervention after clopidogrel pretreatment: the ISAR-REACT 2 randomized trial. JAMA. 2006;295:1531–8. Huang X, Chen S, Redfors B, Zhang Y, Souza CF, Mehran R, et al. Safety and efficacy of bivalirudin monotherapy in patients with non-ST-segment elevation acute coronary syndromes with positive biomarkers undergoing percutaneous coronary intervention: a report from the Acute Catheterization and Urgent Intervention Triage Strategy trial. Coron Artery Dis. 2020;31(1):59–65. Wiśniewski P, Rostoff P, Gajos G, Nessler J, Kruszelnicka O. Predictive value of electrocardiographic ST segment elevation myocardial infarction equivalents for detecting acute coronary artery stenosis in patients with non-ST segment elevation myocardial infarction. Kardiol Pol. 2019;77(6):624–31. Epub 2019 Apr 29. PMID: 31066723. Rostoff P, Wisniewski P, Gajos G, Konduracka E, Nessler J, Kruszelnicka O. Electrocardiographic identification of the culprit coronary artery in acute non-ST-elevation myocardial infarction: predictive value of N-wave and T-wave precordial instability. Coron Artery Dis. 2020;31(7):590–6. 10.1097/MCA.0000000000000918 . Birnbaum Y, Hasdai D, Sclarovsky S, Herz I, Strasberg B, Rechavia E. Acute myocardial infarction entailing ST-segment elevation in lead aVL: electrocardiographic differentiation among stenosis of the left anterior descending, first diagonal, and first obtuse marginal coronary arteries. Am Heart J. 1996;131(1):38–42. 10.1016/s0002-8703(96)90048-4 . Sarıçam E, Erdol MA, Bozkurt E, Ilkay E, Cantekin ÖF. New ECG Algorithm for the Prediction of Culprit Vessel in Acute Myocardial Infarction Involving Lateral Part of the Ventricle: Ilkay Classification. Int J Gen Med. 2023;16:2643–51. PMID: 37377781; PMCID: PMC10292609. Terlecki M, Wojciechowska W, Dudek D, Siusak Z, Plenz K, guzik T, et al. Impact of acute total stenosis of the culprit artery on outcome in NSTEMI based on the results of a large national registry. BMC Cardiovasc Disord. 2021;21:297. Kozuch M, Kralisz P, Rog-Makal M, Bachorzewska-Gajewska H, Dobrzycki S. Significant narrowing of the circumflex artery leads to worse outcomes than right coronary artery narrowing in patients with anterior myocardial infarction treated invasively. Neth Heart J. 2015;23(5):258–62. Sohrabi B, Separham A, Madadi R, Toufan M, Mohammadi N, et al. Difference between Outcome of Left Circumflex Artery and Right Coronary Artery Related Acute Inferior Wall Myocardial Infarction in Patients Undergoing Adjunctive Angioplasty after Fibrinolysis. J Cardiovasc Thorac Res. 2014;6(2):101–4. Sadanandan S, Hochman JS, Kolodziej A, Criger DA, Ross A, Selvester R, et al. Clinical and angiographic characteristics of patients with combined anterior and inferior ST-segment elevation on the initial electrocardiogram during acute myocardial infarction. Am Heart J. 2003;146:653–61. Reichlin T, Abächerli R, Twerenbold R, Kühne M, Schaer B, Müller C et al. Advanced ECG in 2016: is there more than just a tracing? Swiss Med Wkly. 2016;146. 10.4414/smw.2016.14303 . PMID: 27124801. Das MK, Khan B, Jacob S, Kumar A, Mahenthiran J. Significance of a fragmented QRS complex versus a Q wave in patients with coronary artery disease. Circulation. 2006;113(21):2495–501. Niu T, Fu P, Jia C, Dong Y, Liang C, Cao Q, et al. The delayed activation wave in non-ST-elevation myocardial infarction. Int J Cardiol. 2013;162(2):107–11. Cheema A, Khalid A, Wimmer A, Bartone C, Chow T, Spertus JA, et al. Fragmented QRS and mortality risk in patients with left ventricular dysfunction. Circ Arrhythm Electrophysiol. 2010;3(4):339–44. 10.1161/CIRCEP.110.940478 . Colluoglu T, Tanriverdi Z, Unal B, Ozcan EE, Dursun H, Kaya D. The role of baseline and post-procedural frontal plane QRS-T angles for cardiac risk assessment in patients with acute STEMI. Ann Noninvasive Electrocardiol. 2018;23(5). Zhang ZM, Rautaharju PM, Prineas RJ, Tereshchenko LG, Soliman EZ. Electrocardiographic QRS-T angle and the risk of incident silent myocardial infarction in the Atherosclerosis Risk in Communities study. J Electrocardiol. 2017;50:661–6. 10.1016/j.jelectrocard.2017.05.001 . Raposeiras-Roubin S, Virgos‐Lamela A, Bouzas‐Cruz N, Lopez‐Lopez A, Castineira‐Busto M, Fernandez‐Gerda R, et al. Usefulness of the QRS‐T angle to improve long‐term risk stratification of patients with acute myocardial infarction and depressed left ventricular ejection fraction. Am J Cardiol. 2014;113:1312–9. 10.1016/j.amjcard.2014.01.406 . Steg PG, James SK, Atar D. ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation. Eur Heart J., Bassand CW, Agewall JP, Bax S, Boersma J, Bueno E. H, ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. The Task Force for the management of acute coronary syndromes (ACS) in patients presenting without persistent ST-segment elevation of the European Society of Cardiology. Eur Heart J. 2011;32:2999–3054. Hamm CW, Bassand JP, Agewall S, Bax J, Boersma E, Bueno H, et al. ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J. 2011;32:2999–3054. Hygriv Rao B, Rama Raju NS, Srinivasa Raju CS, Patel P, Korabathina R, Raj JP, et al. Metabolic risk factors in first acute coronary syndrome (MERIFACS) Study. Indian Heart J. 2022 Jul-Aug;74(4):275–81. Duc Cong N, Dung HT. The risk factors of acute coronary syndrome in patients over 65 years old at Thong Nhat Hospital of Ho Chi Minh City, Vietnam. J Atheroscler Thromb. 2014;21 Suppl 1. Ralapanawa U, Kumarasiri PVR, Jayawickreme KP, Kumarihamy P, Wijeratne Y, Ekanayake M, et al. Epidemiology and risk factors of patients with types of acute coronary syndrome presenting to a tertiary care hospital in Sri Lanka. BMC Cardiovasc Disord. 2019;19:229. 10.1186/s12872-019-1217-x . Alparslan M. Analysis of door to balloon time in patients with acute coronary syndrome admitted to the emergency department. Kocatepe Med J. 2024;25:117–22. Wang TY, Zhang M, Fu Y, Armstrong PW, Newby LK, Gibson CM, et al. Incidence, distribution, and prognostic impact of occluded culprit arteries among patients with non-ST-elevation acute coronary syndromes undergoing diagnostic angiography. Am Heart J. 2009;157:716–23. Stribling WK, Abbate A, Kontos M, Vetrovec GW, Lotun K. Myocardial infarctions involving acute left circumflex stenosis: Are all stenosiss created equally? Interv Cardiol. 2010;2:695–704. Komatsu J, Nishimura YK, Sugane H, Hosoda H, Imai RI, Nakaoka Y, et al. Acute Left Circumflex Coronary Artery Stenosis: Diagnostic Problems of Initial Electrocardiographic Changes. Circ Rep. 2022;4(10):482–9. Oehler A, Feldman T, Henrikson CA, Tereshchenko LG. QRS-T angle: a review. Ann Noninvasive Electrocardiol. 2014;19(6):534–42. 10.1111/anec.12206 . Aro AL, Huikuri HV, Tikkanen JT. QRS-T angle as a predictor of sudden cardiac death in a middle-aged general population. Europace. 2012;14(6):872–6. Zadeh B, Wambach JM, Lambers M, Nassenstein K, Jensen CJ, Bruder O. QRS-T-angle in patients with ST-Segment Elevation Myocardial Infarction (STEMI): a comparison with cardiac magnetic resonance imaging. Int J Med Sci. 2020;17(15):2264–8. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9169067","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":631146394,"identity":"4a20c9d3-9cea-4584-a3ae-0f477272bc1c","order_by":0,"name":"Evren Dal","email":"data:image/png;base64,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","orcid":"","institution":"University of Health Sciences, Bursa Faculty of Medicine","correspondingAuthor":true,"prefix":"","firstName":"Evren","middleName":"","lastName":"Dal","suffix":""},{"id":631146395,"identity":"cb4cda66-872a-4887-8da0-49758cdc097b","order_by":1,"name":"Suna ERAYBAR","email":"","orcid":"","institution":"University of Health Sciences, Bursa Faculty of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Suna","middleName":"","lastName":"ERAYBAR","suffix":""}],"badges":[],"createdAt":"2026-03-19 11:40:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9169067/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9169067/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108385186,"identity":"7e750b48-3dd6-4bc2-be21-014d93fa52b3","added_by":"auto","created_at":"2026-05-04 06:01:45","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":159373,"visible":true,"origin":"","legend":"\u003cp\u003eElectrocardiogram of a patient showing a narrow QRS-T angle, along with a schematic illustrating the method used to derive the QRS-T angle.\u003c/p\u003e","description":"","filename":"1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9169067/v1/58a5e11b47becc4850d39d4e.jpeg"},{"id":108385187,"identity":"d58f77fd-557c-48fc-840c-e600b3557228","added_by":"auto","created_at":"2026-05-04 06:01:45","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":206267,"visible":true,"origin":"","legend":"\u003cp\u003eElectrocardiogram of a patient showing a wide QRS-T angle, accompanied by a schematic illustrating how the QRS-T angle is derived.\u003c/p\u003e","description":"","filename":"2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9169067/v1/26cc31947839f809ee620707.jpeg"},{"id":108493128,"identity":"e75de317-e447-47b8-b775-fdc47c4e860d","added_by":"auto","created_at":"2026-05-05 09:59:28","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":202492,"visible":true,"origin":"","legend":"\u003cp\u003eIllustration of the N-wave pattern in the inferior leads (II, III, and aVF). The terminal notching of the QRS complex, representing the N-wave, is indicated by blue arrows.\u003c/p\u003e","description":"","filename":"3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9169067/v1/2586f444754286221b71a47e.jpeg"},{"id":108385189,"identity":"dc7cd3d4-a542-4213-8d6f-d69d39487b54","added_by":"auto","created_at":"2026-05-04 06:01:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":28943,"visible":true,"origin":"","legend":"\u003cp\u003eStudy flow chart. CABG: Coronary artery bypass. MI: Myocardial infarction\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9169067/v1/04444a37789075e42a6a62ad.png"},{"id":108492358,"identity":"04fd999a-6f71-4404-8dbb-7ed353278a17","added_by":"auto","created_at":"2026-05-05 09:57:34","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":59729,"visible":true,"origin":"","legend":"\u003cp\u003eROC curve for QRS-T measurement of LCX involvement\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9169067/v1/ceb08b1dabadb9845ea8a5c6.png"},{"id":108803981,"identity":"a80eaf30-cf18-4054-b900-6013d9591255","added_by":"auto","created_at":"2026-05-08 15:13:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1068112,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9169067/v1/28ee28f3-ba68-4a45-8ebd-59e9ab30b4c0.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Emergency Electrocardiographic Assessment of QRS-T Angle and N-Wave for Detecting NSTEMI with Left Circumflex Artery Stenosis","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eOvercrowding in the emergency department is a worldwide problem associated with prolonged hospitalization, poor patient prognosis, and high costs. In early recognition of the critical patient, critical clues guiding assessment in diagnostic processes can be decisive. According to current guidelines, NSTEMI is diagnosed in approximately 10% of patients transferred to emergency departments for chest pain and this rate is gradually increasing [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Patients with NSTEMI with positive biomarkers constitute a high-risk group that is predicted to benefit from invasive treatment and antithrombotic [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. For patients exhibiting at least one high-risk criterion, an early invasive strategy within 24 hours is advisable. These criteria include a confirmed diagnosis of NSTEMI based on the current guidelines, dynamic changes in ST-segment or T waves, transient ST-segment elevation, or a GRACE risk score greater than 140. (1). The diagnosis and initial short-term risk assessment of acute coronary syndromes should be grounded on a combination of factors, including the patient's clinical history, presenting symptoms, vital signs, physical examination findings, ECG results, and hs-cTn levels. Although coronary artery stenosis represents the most common mechanism underlying myocardial infarction, myocardial injury also occur due to alternative mechanisms such as coronary vasospasm, microvascular dysfunction, or supply\u0026ndash;demand mismatch. However, the present study specifically focused on NSTEMI patients with angiographically evaluated coronary arteries in order to investigate the relationship between electrocardiographic parameters and LCX stenosis. Correct management of the diagnostic process of patients presenting with NSTEMI in the emergency department and recognizing very high-risk characteristics to identify which patient will undergo emergency angiography is essential. Analysis and management of the critical patient enable the early intensive care support or needed treatment regimen. The analysis and management of critical patients allow for the timely provision of intensive care support or the necessary treatment regimen.\u003c/p\u003e \u003cp\u003eThe lack of clear findings in NSTMI that point towards ischemia and the expectation of ischemia with the current findings delay the diagnostic process in the emergency department. For this purpose, research on the efficacy of NSTEMI findings, especially those evaluated at the time of initial presentation, in the diagnosis of NSTEMI continues in the literature. [\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe STEMI-NSTEMI paradigm is based on the observation that ST elevation on the electrocardiogram in most MI patients is related to acute occlusion of the infarct-related artery. Unstable angina represents another component of the acute coronary syndrome spectrum; however, because it is not associated with detectable myocardial necrosis or biomarker elevation, these patients were not included in the present study, which specifically focused on NSTEMI cases with positive troponin levels. Subtotal stenosis often cause ST segment depression and negative T waves on the ECG. The prognosis following acute myocardial infarction is related to the localization of the infarction, the responsible coronary artery, and the level of stenosis of the coronary artery [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. It is predicted that LCX artery stenosis are responsible for 20% of MIs. LCX involvement is underrecognized in patients presenting with acute coronary syndromes, particularly when classical ST-segment elevation patterns are absent on the standard 12-lead ECG. In such cases, the diagnosis is not based on ECG alone but on the integration of clinical presentation, cardiac biomarkers (troponins), and ECG findings, consistent with the inclusion criteria defined in the Materials and Methods section. When LCX involvement is suspected, additional posterior ECG leads provide complementary diagnostic information.. These patients are more likely to undergo percutaneous coronary intervention more than 24 hours following the onset of symptoms compared with patients with more easily recognizable left anterior descending (LAD) and right coronary artery (RCA) stenosis [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLCX occlusion should be considered in clinical pictures consistent with ACS despite non-diagnostic ECG findings. ST segment elevation exists in less than half of patients with LCX occlusion. ST segment elevation in D1 and AVL derivations or isoelectricity of the ST segment is common in patients with inferior myocardial infarction due to LCX stenosis. In addition, maximum ST segment depression in V2 or V3, seen in precordial derivations, has been found to have a specificity of 96% and a sensitivity of 70% for LCX stenosis [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The absence of ST segment depression or even ST segment elevation in AVL shows LCX stenosis.\u003c/p\u003e \u003cp\u003eIn the literature, the number of data showing the frequency and amount of ST segment and T wave changes on ECG due to isolated acute stenosis of LCX and their relationship with the level of stenosis is limited. In addition, in cases in which the left main coronary artery, left anterior descending artery (LAD), intermediate artery, right coronary artery, and their major branches are normal or no significant stenosis is found coronary angiographically, there is no adequate data indicating the presence, shape, and frequency of ST segment and T wave changes that develop in inferior, posterior and anterior derivations on ECG due to stenosis of the LCX alone [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eECG has long been a hot topic for researchers in the identification of the responsible coronary artery, prediction of the level of artery stenosis, and prognosis of patients with NSTEMI. Fragmented QRS (fQRS) is a new depolarization abnormality defined by Das et al. in 2006 as the presence of an additional R wave (R') or the presence of notching at the end of the R or S wave or the presence of more than one R' in 2 consecutive derivations corresponding to the supply territory of a major coronary artery [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Niu et al. interpreted the appearance of a notch in the terminal part of the QRS in DII; III, AVF or DI AVL as N wave in acute NSTEMI in the presence of the responsible lesion circumflex artery (LCX) and found it significant with a sensitivity of 77% and a specificity of 96% in circumflex artery lesions. The role of the N wave and whether this wave can be considered as an ST segment are not clear [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eQRS-T angle, a new marker of ventricular repolarization heterogeneity, is defined as the angle difference between the direction of ventricular depolarization (QRS wave) and the direction of ventricular repolarization (T wave). The QRS-T angle in the frontal plane can be easily measured from the automatic report section of ECG devices and shows a good correlation with the spatial QRS-T angle in risk prediction. Studies have demonstrated the prognostic value of f(QRS-T) angle in different populations. It has been shown that a wide f(QRS-T) angle (\u0026gt;\u0026thinsp;90\u0026deg;) is a good predictor of long-term mortality in patients with left ventricular systolic dysfunction after acute myocardial infarction [\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. This change, which occurs as a result of impaired ventricular depolarization and repolarization, indicate an ischemic area and predict a significant change to indicate the responsible lesion.\u003c/p\u003e \u003cp\u003eSeeing important clues in patients evaluated in the emergency department with chest pain and suspected acute coronary syndrome in the etiology make important contributions to patient management. Particularly in cases of acute coronary syndrome without ST segment elevation, obtaining information about stenosis localization and recognizing the critical patient can shorten serial troponin monitoring and emergency department follow-up time. Predicting the need for coronary angiography or intensive care with the ECG taken at the time of admission can have positive effects on survival. At this point, the evaluation of the QRS-T angle, which is often left out in routine use, and the N wave, which is a form of QRS fragmentation, can provide important information as an additional ECG finding in deciding the severity of patients, early consultation, or imaging decisions for patients.\u003c/p\u003e \u003cp\u003ePrevious studies investigating ECG predictors of LCX stenosis have been mainly conducted in cardiology settings and often focused on single parameters such as the N-wave or QRS-T angle. In contrast, our study evaluates both parameters simultaneously in NSTEMI patients at the point of emergency admission, aiming to determine their early diagnostic contribution before invasive procedures.\u003c/p\u003e \u003cp\u003eThis study aims to evaluate the relationship between acute stenosis of isolated LCX on admission ECG and the presence of QRS-T angle and N wave, which are measures reflecting ventricular repolarization and depolarization on ECG, and to examine their role in determining the level of stenosis in patients with NSTEMI.\u003c/p\u003e"},{"header":"2. METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Patient Selection\u003c/h2\u003e \u003cp\u003ePatients who presented with ischemic chest pain or angina equivalent symptoms in the emergency department of our hospital in the 1-year period between May 1, 2022 and May 1, 2023, and who were diagnosed with NSTEMI as a result of cardiology consultation with positive serial troponin monitoring and were hospitalized in coronary intensive care unit were retrospectively evaluated. Written permission was obtained from the ethics committee of our hospital during the study planning phase (2019-KAEK-140 2023-11/8). Patients with ST segment elevation on emergency admission ECG, history of previous MI or coronary artery bypass (CABG) and patients whose ECG data were not available were excluded. Patients with prior myocardial infarction or CABG were excluded to avoid chronic repolarization abnormalities on ECG that could interfere with the assessment of acute ischemic finding.J point was used to determine the amount of ST change and pathologic Q wave, \"ST elevation\" and \"ST depression\" were determined according to the criteria specified in ESC/ACC [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Age, gender, comorbidities, emergency department presentation symptoms, and pain characteristics of the patients were recorded. Medical histories, including previously known diagnoses such as coronary artery disease, hypertension, diabetes mellitus, and heart failure, were reviewed from hospital records. The length of stay in the emergency department and the time until angiography were calculated.\u003c/p\u003e \u003cp\u003e All included patients underwent coronary angiography according to current NSTEMI management guidelines after cardiology consultation, based on elevated cardiac troponin levels and supportive ischemic ECG findings\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Coronary Angiography results\u003c/h2\u003e \u003cp\u003eThe results of the investigations and the pathologies and interventions detected by coronary angiography were recorded on the patient files registered in the hospital automation system. Coronary angiography was performed by the interventional cardiology team as part of routine clinical care. The angiographic reports were retrospectively reviewed by the authors, and the severity of stenosis was determined according to the cardiologists\u0026rsquo; visual assessment. Lesions with \u0026ge;\u0026thinsp;70% luminal narrowing were considered significant. In this study, the term \u0026ldquo;stenosis\u0026rdquo; refers to partial luminal narrowing, whereas \u0026ldquo;occlusion\u0026rdquo; was used to describe complete (100%) obstruction of the coronary artery. Initially, patients with total occlusion or critical stenosis in LCX but with completely normal or less than 70% lesions in other coronary arteries were included in the evaluation. The stenosis in the LCX was classified according to its location as central (proximal segment, obtuse marginal branch, and intermediate branch) and peripheral (atrial branch, peripheral distal segment, posterolateral branch (Omi 2), and posterior descending branch).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Electrocardiographic measurements\u003c/h2\u003e \u003cp\u003eElectrocardiographic measurements were performed on the standard 12-leads ECG and, if available, on the posterior ECG recordings obtained at emergency department admission just before coronary angiography was performed. The QRS-T angle in the frontal plane was recorded from the automatic report section of the ECG devices and calculated automatically. The frontal QRS-T angle was considered as the difference between the frontal plane QRS axis and the T axis (Figure:1). If such a difference exceeded 180\u0026deg;, the frontal QRS-T angle was calculated as 360\u0026deg; minus the absolute value of the difference between the frontal plane QRS axis and the T axis (Figure:2). The N wave was defined as the appearance of a notch in the terminal part of the QRS in DII; III, AVF or DI AVL. (Figure: 3). ECGs were manually reviewed by the responsible investigators, blinded to the angiographic findings. Final confirmation was made by consensus between authors.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analyses were conducted in Jamovi 2.3.28 package program. While descriptive statistics of the qualitative variables in the study were presented with frequency and percentage, quantitative variables were given with mean, standard deviation, median, and minimum and maximum values. The conformity of quantitative variables to normal distribution was examined by the Shapiro-Wilk test. Independent sample t-test and Mann Whitney U test were used for independent 2-group comparisons of quantitative variables. The discrimination of the QRS-T variable according to LCX involvement and N wave was analyzed by ROC analysis. The relationships between quantitative variables were analyzed with the Pearson correlation coefficient. In all statistical analyses in the study, results with a p-value below 0.05 were considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. RESULTS","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Patient Demographics and Baseline Characteristics\u003c/h2\u003e\n \u003cp\u003eA total of 490 patient data were retrospectively reviewed within the scope of our study. 210 patients were excluded due to STEMI detection, and 27 patients were excluded due to inaccessible study data. A total of 253 patients were included in the study. The inclusion status of patients is summarized in the study flow chart (Figure:4).\u003c/p\u003e\n \u003cp\u003eThe median age was 63 years (min: 34, max: 86), and 70% (n: 177) were male. Regarding chronic diseases, hypertension was the most common, affecting 74.4% (n: 189) of patients, followed by coronary artery disease (42.3%, n: 107) and diabetes mellitus (21.3%, n: 54). Chronic renal failure was present in 6.7% (n: 17), but no history of dialysis was recorded. Chest pain was recorded as typical ischemic chest pain in 66% of patients, with sweating and new-onset dyspnea considered as angina equivalent in 13.4% (n: 34). Patient characteristic\u0026rsquo;s summarized in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePatient Characteristics and Clinical Data\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCategory\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGender\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e177\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e70.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStent Presence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbsent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e87.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDiabetes Mellitus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e199\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e78.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHypertension (HT)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e189\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e74.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eKnown Coronary Artery Disease history\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e146\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e57.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e42.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChronic Renal Failure (CRF)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e93.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHeart Failure (HF)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e87.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAsthma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e253\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMalignancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e253\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChest Pain Characteristics\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTypical\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e66.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAtypical\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAdditional symptoms Dyspnea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNausea/Vomiting\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSweating\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFatigue\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEpigastric Pain\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Clinical and Angiographic Findings\u003c/h2\u003e\n \u003cp\u003eThe median door-to-balloon time between emergency department evaluation and coronary angiography was 478 minutes. According to coronary angiography, 77.1% (n: 195) of patients had multivessel stenosis, 69.2% (n: 175) had circumflex artery stenosis, and 47.4% (n: 120) had stenosis\u0026thinsp;\u0026gt;\u0026thinsp;70%. (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eProcedural Characteristics and Angiographic Results\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAngiographic Result\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCategory\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLAD Occlusion\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;70%\u003c/p\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;70%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003cp\u003e136\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.3\u003c/p\u003e\n \u003cp\u003e22.1\u003c/p\u003e\n \u003cp\u003e66.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eRCA Occlusion\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;70%\u003c/p\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;70%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003cp\u003e59\u003c/p\u003e\n \u003cp\u003e83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30.4\u003c/p\u003e\n \u003cp\u003e40.7\u003c/p\u003e\n \u003cp\u003e30.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLCX Occlusion\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;70%\u003c/p\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;70%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\"\u003e\n \u003cp\u003e78\u003c/p\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30,8\u003c/p\u003e\n \u003cp\u003e21.7\u003c/p\u003e\n \u003cp\u003e47.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 QRS-T Angle and Vessel Involvement\u003c/h2\u003e\n \u003cp\u003eAnalysis of QRS-T values showed a significant difference between groups based on vessel involvement (p\u0026thinsp;=\u0026thinsp;0.004). The QRS-T values were significantly higher in the multivessel group. However, no statistically significant difference was found between the percentage of LCX stenosis and the QRS-T angle (Table\u0026nbsp;3).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTable-3\u0026nbsp;\u003c/strong\u003eVessel involvement and QRS-T angle value\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth colspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAngiographic vessel involvement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSingle Vessel\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMulti Vessel\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T \u003cstrong\u003eangle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e51.51\u0026thinsp;\u0026plusmn;\u0026thinsp;47.26\u003c/p\u003e\n \u003cp\u003e33 (\u0026minus;\u0026thinsp;189)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e81.19\u0026thinsp;\u0026plusmn;\u0026thinsp;62.94\u003c/p\u003e\n \u003cp\u003e64 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0,004\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLCX Stenosis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;70% Stenosis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026gt;\u0026thinsp;70.Stenosis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T \u003cstrong\u003eangle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63.16\u0026thinsp;\u0026plusmn;\u0026thinsp;45.98\u003c/p\u003e\n \u003cp\u003e52 (2\u0026ndash;158)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e89.49\u0026thinsp;\u0026plusmn;\u0026thinsp;69.83\u003c/p\u003e\n \u003cp\u003e65 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.122\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003e\u003csup\u003ea\u003c/sup\u003eMann Whitney U test\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Impact of Proximal LCX Involvement on QRS-T Angle\u003c/h2\u003e\n \u003cp\u003eWhen analyzing the change in QRS-T angle values with respect to LCX involvement site, a statistically significant difference was observed in QRS-T between patients with and without involvement in the proximal segment (p\u0026thinsp;=\u0026thinsp;0.012). QRS-T values were higher in patients with proximal segment involvement (Table\u0026nbsp;4).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTable-4\u0026nbsp;\u003c/strong\u003eQRS-T angle value and LCX involvement site\u0026nbsp;\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tabb\" border=\"1\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eProximal segment\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;140)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e65,66\u0026thinsp;\u0026plusmn;\u0026thinsp;52,03\u003c/p\u003e\n \u003cp\u003e55 (1\u0026ndash;221)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0,012\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;64)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95,84\u0026thinsp;\u0026plusmn;\u0026thinsp;73,17\u003c/p\u003e\n \u003cp\u003e78 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eObtus marginalis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;174)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e73,69\u0026thinsp;\u0026plusmn;\u0026thinsp;59,66\u003c/p\u003e\n \u003cp\u003e59,5 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0,807\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;31)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e80,84\u0026thinsp;\u0026plusmn;\u0026thinsp;67,80\u003c/p\u003e\n \u003cp\u003e62 (1\u0026ndash;245)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eIntermediate branch\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;150)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e70,15\u0026thinsp;\u0026plusmn;\u0026thinsp;58,07\u003c/p\u003e\n \u003cp\u003e56 (1\u0026ndash;244)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0,105\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;55)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e87,38\u0026thinsp;\u0026plusmn;\u0026thinsp;66,74\u003c/p\u003e\n \u003cp\u003e69 (2\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAtrial branch\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;197)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e74,21\u0026thinsp;\u0026plusmn;\u0026thinsp;61,21\u003c/p\u003e\n \u003cp\u003e59 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0,348\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;8)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e88,50\u0026thinsp;\u0026plusmn;\u0026thinsp;52,11\u003c/p\u003e\n \u003cp\u003e84,5 (1\u0026ndash;158)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePeripheral distal segment\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;164)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e73,31\u0026thinsp;\u0026plusmn;\u0026thinsp;61,55\u003c/p\u003e\n \u003cp\u003e57 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0,306\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;41)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e80,63\u0026thinsp;\u0026plusmn;\u0026thinsp;58,25\u003c/p\u003e\n \u003cp\u003e65 (6\u0026ndash;249)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePosterolateral branch\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;185)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e74,64\u0026thinsp;\u0026plusmn;\u0026thinsp;61,75\u003c/p\u003e\n \u003cp\u003e61 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0,769\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;20)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e76,00\u0026thinsp;\u0026plusmn;\u0026thinsp;53,05\u003c/p\u003e\n \u003cp\u003e55 (3\u0026ndash;151)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePosterior descending branch\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo (n\u0026thinsp;=\u0026thinsp;203)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e74,09\u0026thinsp;\u0026plusmn;\u0026thinsp;59,84\u003c/p\u003e\n \u003cp\u003e60 (1\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes (n\u0026thinsp;=\u0026thinsp;2)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003e\u003csup\u003ea\u003c/sup\u003eMann Whitney U test; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{x}\\)\u003c/span\u003e\u003c/span\u003e\u0026plusmn;s; median (min \u0026ndash; max)\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Sensitivity and Specificity of QRS-T for LCX Involvement\u003c/h2\u003e\n \u003cp\u003eRegarding the discriminatory power of QRS-T for LCX involvement, ROC analysis showed significant discrimination with a sensitivity of 35.92% and specificity of 84.13% for a QRS-T value of 100 (AUC\u0026thinsp;=\u0026thinsp;0.586; p\u0026thinsp;=\u0026thinsp;0.039) (Figure:5)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 N Wave Analysis and Correlation with Vessel Pathology\u003c/h2\u003e\n \u003cp\u003eThe presence of N waves was detected in 46 (22.5%) ECGs. No statistically significant difference was found between the presence of N waves and multivessel involvement in coronary angiography (p\u0026thinsp;=\u0026thinsp;0.469). Similarly, no significant relationship was observed between N waves and QRS-T values (p\u0026thinsp;=\u0026thinsp;0.141) (Table\u0026nbsp;5). Additionally, there was no significant correlation between N wave presence and CX stenosis status, percentage, or regions (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;6).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTable-5\u003c/strong\u003e Relation of N wave and vessel involvement and QRS-T angle\u0026nbsp;\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003ctable id=\"Tabd\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth colspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAngiographic vessel involvement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSingle Vessel\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMulti Vessel\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eN wave\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3 (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34 (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0.469\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1 (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7 (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eN wave\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71.23\u0026thinsp;\u0026plusmn;\u0026thinsp;58.59\u003c/p\u003e\n \u003cp\u003e55 (1\u0026ndash;244)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e87.70\u0026thinsp;\u0026plusmn;\u0026thinsp;67.51\u003c/p\u003e\n \u003cp\u003e73 (2\u0026ndash;255)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.141\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003e\u003csup\u003ea\u003c/sup\u003eYates chi-square test, \u003csup\u003eb\u003c/sup\u003eMann Whitney U test\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cstrong\u003eTable-6\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eRelation of vascular stenosis percentage and N wave\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003ctable id=\"Tabe\" border=\"1\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd colspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eN wave\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLAD Stenosis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19 (%12.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4 (%8.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0.716\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSingle vessel\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e139 (%88.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e42 (%91.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLAD Stenosis %\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;70%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31 (%22.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14 (%33.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0.213\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026gt;\u0026thinsp;70%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e108 (%77.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28 (%66.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eRCA Stenosis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e48 (%30.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14 (%30.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e1.000\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSingle vessel\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e110 (%69.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32 (%69.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eRCA Stenosis %\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;70%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49 (%44.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10 (%31.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e0.255\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026gt;\u0026thinsp;70%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e61 (%55.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22 (%68.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003e\u003csup\u003ea\u003c/sup\u003eYates chi-square test\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 Correlation of QRS-T Angle with Troponin Levels\u003c/h2\u003e\n \u003cp\u003eA very weak positive correlation was observed between troponin values and QRS-T angle value. However, no significant correlation was found for LCX involvement specific to the affected vasculature, independent of the level of involvement (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e). When the effect of the presence of N waves on the change in QRS-T angle value and troponin levels was analyzed, a weak positive correlation was found between QRS-T and troponin values in patients without N waves, but no significant correlation was observed in patients with N waves.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eQRS-T angle value differences due to LCX stenosis degree and N wave\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eGeneral\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTroponin-1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTroponin-2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTroponin-3\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003er\u0026thinsp;=\u0026thinsp;0,171\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ep\u0026thinsp;=\u0026thinsp;0,014\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003er\u0026thinsp;=\u0026thinsp;0,167\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ep\u0026thinsp;=\u0026thinsp;0,017\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003er\u0026thinsp;=\u0026thinsp;0,203\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ep\u0026thinsp;=\u0026thinsp;0,006\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLCX\u0026thinsp;\u0026lt;\u0026thinsp;70%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,174\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,258\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,085\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,587\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,209\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,221\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLCX\u0026thinsp;\u0026gt;\u0026thinsp;70%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,101\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,322\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,161\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,114\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,137\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,195\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eN wave negativity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003er\u0026thinsp;=\u0026thinsp;0,162\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ep\u0026thinsp;=\u0026thinsp;0,042\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003er\u0026thinsp;=\u0026thinsp;0,166\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ep\u0026thinsp;=\u0026thinsp;0,037\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003er\u0026thinsp;=\u0026thinsp;0,232\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ep\u0026thinsp;=\u0026thinsp;0,005\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eN wave positivity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eQRS-T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,168\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,264\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,202\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003er\u0026thinsp;=\u0026thinsp;0,227\u003c/p\u003e\n \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0,177\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003e\u003cem\u003er: Pearson correlation coefficient\u003c/em\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. DISCUSSION","content":"\u003cp\u003eDespite advances in the treatment of cardiovascular diseases, acute coronary syndromes remain a major cause of morbidity and mortality. ST-segment elevation alonenot always reflect ongoing ischemia, and it is no longer sufficient to focus on the presence or absence of ST-segment elevation as a reliable criterion to proceed with or postpone emergency angiography and/or reperfusion therapy. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] Therefore, it is now important to recognize acute coronary syndrome without ST-segment elevation early and promptly refer to necessary reperfusion therapies.\u003c/p\u003e \u003cp\u003eHypertension (HT) and diabetes mellitus (DM) constitute an important part of the known risk factors for acute coronary syndrome [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The prevalence of HT and DM was found to be 84.6% and 29.0% higher in the elderly group compared to the non-elderly group, respectively [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Similar to the literature, HT was the chronic disease with the highest prevalence in our study, followed by coronary artery disease.\u003c/p\u003e \u003cp\u003eAlthough the importance of managing the diagnostic process in the emergency department admission ECG in the presence of STEMI and taking the patient to percutaneous coronary intervention within 90 minutes is clearly stated in the literature, the optimal time in non-STEMI and USAP is changeable. For these patients, waiting in the emergency department for investigations or repeated enzyme monitoring prolongs the follow-up time. In addition, since the stenosis level of these patients cannot be clearly evaluated, there is no consensus on the required time. In our study, the median time to percutaneous intervention was 478 (min:1-max:17826) minutes. In cases with NSTEMI and USAP, there are studies showing that PCI was performed within 5 minutes at the earliest, 1440 minutes at the latest and 285.44\u0026thinsp;\u0026plusmn;\u0026thinsp;265.79 minutes on average [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. This temporal variation suggests that the decision was made based on the patient's clinic and complete stenosis was ignored.\u003c/p\u003e \u003cp\u003e. In studies, among NSTEMI patients with LCX stenosis, those presenting with ST-segment depression were associated with larger infarct size and advanced acute heart failure than those without ST-segment changes [\u003cspan additionalcitationids=\"CR27\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Similar to the literature, in our study conducted in NSTEMI patients, a critical LCX lesion accompanying RCA stenosis was found in 47.4%.\u003c/p\u003e \u003cp\u003eThe QRS-T angle, a measurement from vector electrocardiography analysis, has been thoroughly researched since 1934 when Wilson and his team introduced the \"ventricular gradient.\" This gradient, representing the combined spatial QRS-T angle, was believed to show the variability in action potential shapes, be mostly unaffected by the sequence of ventricular activation, and represent the \"primary T-wave\" or initial differences in repolarization.\u003c/p\u003e \u003cp\u003eIn contrast to the spatial ventricular gradient, the spatial QRS-T angle indicates a \"secondary T-wave,\" which reflects repolarization abnormalities caused by depolarization issues, such as premature ventricular contractions, ventricular pacing, and bundle branch blocks, rather than primary differences in action potential shapes. Therefore, the QRS-T angle complements the ventricular gradient, and both can be used to evaluate patients with primary, secondary, or mixed repolarization abnormalities, like those found in left ventricular hypertrophy (LVH) (29).\u003c/p\u003e \u003cp\u003eA wide QRS-T angle (\u0026ge;\u0026thinsp;90\u0026deg;), a marker of myocardial depolarization and repolarization as one of many electrocardiogram parameters, appears to be associated with electrical instability and has been associated with cardiac prognosis in several studies (29\u0026ndash;31). In addition to traditional cardiac risk factors, QRS-T angle has been shown to contribute to the prediction of the risk of sudden cardiac death after ACS (e). Although studies have shown changes in the frontal QRS-T angle due to disturbances in coronary blood flow, it has not been found to be associated with the percentage of coronary involvement on coronary angiograms in NSTEMI patients. In our study, QRS-T angle was found to be significantly higher in multivessel involvement.\u003c/p\u003e \u003cp\u003eACS patients with ST-segment depression or without significant ST-segment changes are considered to have non-transmural infarction without vessel stenosis and usually do not undergo urgent coronary reperfusion. In this context, ACS with LCX stenosis often creates diagnostic problems and leads to late recognition of vessel stenosis. Diagnosis of acute LCX stenosis by standard 12-lead ECG is often difficult because more than half of acute LCX stenosis occur without characteristic ST-segment elevation on the ECG. When we looked at whether the QRS-T measurement was discriminative for LCX stenosis, the ROC analysis showed that it was significantly discriminative with 35.92% sensitivity and 84.13% specificity for QRS-T\u0026thinsp;=\u0026thinsp;100 (AUC\u0026thinsp;=\u0026thinsp;0.586; p\u0026thinsp;=\u0026thinsp;0.039). Accordingly, evaluation of the frontal QRS-T angle on ECG, a simple and practical method, provide additional information for the early recognition of high-risk patients and assist in planning early revascularization strategies in clinical practice.\u003c/p\u003e \u003cp\u003eIn the evaluation of LCX lesion localization, it was observed that the QRS-T angle was determinative especially in LCX proximal segment stenosis, despite its insufficiency in showing the percentage of LCX stenosis. It is thought that proximal LCX lesions are frequently encountered in patients without ST segment depression or ST segment change [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The ST segment pattern and QRS-T angle should be interpreted carefully since large infarct areas caused by proximal LCX stenosis is present and result in cardiac failure in the advanced period.\u003c/p\u003e \u003cp\u003eThe lack of clear ECG findings in the diagnosis of NSTEMI has led many studies to identify new electrocardiographic indicators of coronary artery occlusion, such as the delayed activation wave or N-wave, which have been described as STEMI equivalents [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In our study, however, no significant relationship was observed between the presence of the N-wave and LCX stenosis. Previous reports by Niu et al. and Rostoff et al. demonstrated a strong association between the N-wave and circumflex lesions, but these studies included heterogeneous populations with unstable angina, multivessel involvement, and variable ischemic phases [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In contrast, our cohort consisted exclusively of patients with NSTEMI and angiographically isolated LCX stenosis, evaluated using ECGs obtained at emergency department admission. The discrepancy between our results and previous studies therefore reflect methodological and population differences, as well as variations in the definition and timing of N-wave assessment across studies. Although our study did not demonstrate a significant association between N wave and LCX stenosis, this finding contributes to the growing variability in the literature regarding the diagnostic meaning of this ECG pattern. Previous studies have reported different rates of N wave positivity depending on the population studied, the inclusion of anterior or inferior infarctions, and the definition thresholds applied. It is possible that N wave reflects a spectrum of ischemic and repolarization changes rather than a lesion-specific marker. In this context, our results support the view that N wave alone not indicate LCX-related ischemia but should be interpreted together with other ECG parameters and clinical findings in the emergency setting.\u003c/p\u003e \u003cp\u003eCorrect management of the diagnostic process of patients presenting with acute coronary syndrome in the emergency department is completed by detailed analysis of the admission ECG and interpretation of the repeated troponin test result. In the presence of NSTEMI, correct recognition of the patient and prolonging the follow-up period by making risk classifications are effective in the correct management of this process. The relationship between the QRS-T angle and troponin levels was examined at the point of interpreting troponin test results and ECG findings together. A weak correlation was found between the QRS-T angle value and troponin levels, which suggests that QRS-T angle should be evaluated as an early clue of the change in ventricular depolarization-repolarization cycle and myocardial necrosis. Additional studies are needed in this regard. Future multicenter prospective studies including larger patient populations and integrating additional electrocardiographic and imaging parameters provide a more comprehensive evaluation of the diagnostic value of the QRS-T angle in NSTEMI patients.\u003c/p\u003e"},{"header":"5. CONCLUSION","content":"\u003cp\u003eThe QRS-T angle reflects abnormalities in ventricular depolarization and repolarization that occur during myocardial ischemia. In the present study, an increased QRS-T angle was associated with the presence of LCX stenosis in patients with NSTEMI. However, this parameter appears to reflect ischemia-related electrical changes rather than the anatomical severity of coronary artery stenosis. These findings should be interpreted cautiously given the modest discriminatory performance observed in the ROC analysis (AUC\u0026thinsp;=\u0026thinsp;0.586). Accordingly, although the QRS-T angle provide supportive electrocardiographic information suggesting LCX-related ischemia, it has limited ability to distinguish between different degrees of stenosis or to predict total occlusion. Left circumflex (LCX) occlusion or infarct-related artery stenosis results in a higher risk of major adverse cardiac events (MACE), delayed diagnosis, and inappropriately prolonged time to revascularization. Having important clues on the admission ECG in patients evaluated in the emergency department with chest pain and a suspected etiology of acute coronary syndrome can contribute to patient management and help in the early identification of Non STEMI patients. ST-segment changes on the 12-lead electrocardiogram can be used to distinguish between circumflex artery stenosis and right coronary artery stenosis. Knowing which vessel is occluded before percutaneous coronary intervention help in planning the procedure and in recognizing patients at high risk for conduction disturbances in the atrioventricular node.\u003c/p\u003e"},{"header":"6. LIMITATIONS","content":"\u003cp\u003eThe first limitation of our study is that it was a single-center and retrospective study. There was a loss of data due to the use of chart review. As a single-center retrospective study, our findings not be generalizable to different populations or healthcare settings, which limits the external validity of the results. The second limitation is that the percentages of stenosis detected in the angiographic results were evaluated and no comment could be made on the ischemic area and the responsible lesion. In-hospital outcomes, including complications, revascularization, or MACE, could not be evaluated due to incomplete inpatient data. In our study, the relationship between QRS-T angle and 28- and 90-day mortality could not be evaluated due to insufficient quantitative variables. The 90-day frequency of cardiac adverse events was also not evaluated due to lack of data. In addition, the effects of medications on ECG parameters and potential variations related to lead placement or patient body habitus could not be fully controlled, representing additional technical limitations of the study. Large-scale studies on this subject are needed.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cul\u003e\n \u003cli\u003eNSTEMI: Non-ST-segment elevation myocardial infarction\u003c/li\u003e\n \u003cli\u003eLCX: Left circumflex artery\u003c/li\u003e\n \u003cli\u003eECG: Electrocardiogram\u003c/li\u003e\n \u003cli\u003eROC: Receiver operating characteristic\u003c/li\u003e\n \u003cli\u003eAUC: Area under the curve\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Declarations","content":"\u003cp\u003eThere is no competing interest between authors. There is no financial and nonfinancial funding source to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis retrospective study was approved by the Ethics Committee of \u003cstrong\u003eBursa Sehir Training and Research Hospital, University of Health Sciences, Turkey\u003c/strong\u003e (Approval No. 2019-KAEK-140 2023-11/8).\u003c/p\u003e\n\u003cp\u003eThe study was conducted in accordance with the principles of the \u003cstrong\u003eDeclaration of Helsinki\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eDue to the retrospective nature of the study and the use of anonymized patient data, \u003cstrong\u003einformed consent to participate was waived by the Ethics Committee\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are not publicly available due to patient confidentiality but are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eE.D. conceptualized the study, analyzed the data, and drafted the manuscript.\u003cbr\u003e\u0026nbsp;S.E. contributed to data collection, interpretation, and critical revision of the manuscript.\u003cbr\u003e\u0026nbsp;All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the medical and administrative staff of Bursa Sehir Training and Research Hospital for their support during data collection.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMembers WC, Gulati M, Levy PD, Mukherjee D, Amsterdam E, Bhatt DL, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain: a report of the American College of Cardiology/American Heart Association joint committee on clinical practice guidelines. 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Int J Med Sci. 2020;17(15):2264\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-cardiovascular-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcar","sideBox":"Learn more about [BMC Cardiovascular Disorders](http://bmccardiovascdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcar/default.aspx","title":"BMC Cardiovascular Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Acute coronary syndrome, NSTEMI, QRS-T angle, N wave, fragmented QRS, LCX stenosis","lastPublishedDoi":"10.21203/rs.3.rs-9169067/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9169067/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eEarly identification of left circumflex artery (LCX) stenosis in patients with non-ST-segment elevation myocardial infarction (NSTEMI) is challenging due to often non-diagnostic electrocardiographic (ECG) findings. This study evaluated the diagnostic value of the frontal QRS-T angle and N-wave presence on admission ECG for detecting LCX stenosis.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis retrospective study included 253 NSTEMI patients admitted between May 2022 and May 2023. All patients underwent coronary angiography, with \u0026ge;\u0026thinsp;70% stenosis defined as significant. The frontal QRS-T angle was obtained from automated ECG reports, and N waves were assessed manually. Statistical analyses included group comparisons and receiver operating characteristic (ROC) analysis to determine the discriminatory ability of QRS-T angle for LCX involvement.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eLCX stenosis was present in 69.2% of patients, with 47.4% showing significant stenosis. The QRS-T angle was significantly higher in patients with multivessel disease (p\u0026thinsp;=\u0026thinsp;0.004) and proximal LCX involvement (p\u0026thinsp;=\u0026thinsp;0.012), but not associated with stenosis severity (p\u0026thinsp;=\u0026thinsp;0.122). ROC analysis demonstrated modest discrimination for LCX involvement (AUC\u0026thinsp;=\u0026thinsp;0.586, p\u0026thinsp;=\u0026thinsp;0.039), with a cut-off of 100\u0026deg; yielding 35.92% sensitivity and 84.13% specificity. N-wave presence showed no significant association with LCX stenosis or QRS-T angle (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe frontal QRS-T angle provide supportive diagnostic information for LCX involvement in NSTEMI, particularly in proximal lesions, but has limited ability to predict stenosis severity. N-wave presence was not a reliable indicator. The QRS-T angle serve as an adjunct ECG marker when interpreted alongside clinical and biochemical findings.\u003c/p\u003e","manuscriptTitle":"Emergency Electrocardiographic Assessment of QRS-T Angle and N-Wave for Detecting NSTEMI with Left Circumflex Artery Stenosis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-04 06:01:41","doi":"10.21203/rs.3.rs-9169067/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-05T11:28:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"84702592641891071417375362968047739731","date":"2026-04-23T10:59:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-22T16:32:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"118664000964678610657847004888557604404","date":"2026-04-22T16:26:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-21T08:55:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-31T08:59:48+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-03-27T13:38:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-27T11:29:21+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Cardiovascular Disorders","date":"2026-03-27T11:24:24+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-cardiovascular-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcar","sideBox":"Learn more about [BMC Cardiovascular Disorders](http://bmccardiovascdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcar/default.aspx","title":"BMC Cardiovascular Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e82273ed-2b86-4b0c-b54e-428230c7bdc1","owner":[],"postedDate":"May 4th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-05T11:28:37+00:00","index":65,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-04T06:01:41+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-04 06:01:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9169067","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9169067","identity":"rs-9169067","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}