Modified stepwise method with the guidance of QDOT MICRO catheter for mitral isthmus ablation in patients with persistent atrial fibrillation

Modified stepwise method with the guidance of QDOT MICRO catheter for mitral isthmus ablation in patients with persistent atrial fibrillation | 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 Modified stepwise method with the guidance of QDOT MICRO catheter for mitral isthmus ablation in patients with persistent atrial fibrillation Jingchao Li, Chaoyu Zhao, Luqian Cui, Xin Wang, Qianqian Feng, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8308466/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Ethanol infusion of the vein of Marshall (EI-VOM) has elevated the success rate of mitral isthmus (MI) block in patients with persistent atrial fibrillation (PeAF). However, the procedure involve the extensive endocardial ablation and epicardial ablation, which brought the operational difficulty and risk. Objectives This study aimed to investigate the value of QDOT MICRO (QDM) catheter in mapping the potential of VOM and guiding MI ablation in patients with PeAF. Methods Patients with PeAF were randomly assigned in a 1:1 ratio to either STSF catheter group using the stepwise method (STSF group) or QDM catheter group using a modified stepwise method (QDM group) for MI ablation. The modified stepwise method was as follows: step 1, The potential of VOM was mapped from endocardium using the QDM catheter. Step 2, EI-VOM. Step 3, precise endocardial ablation guiding by VOM potential. Step 4, QDM catheter was cannulated into the CS for epicardial ablation, especially the ostium of Marshall. The immediate procedural results were compared between the two groups. Results After excluding 5 patients with unsuccessful EI-VOM, 68 patients were divided into STSF group (36 cases) and QDM group (32 cases). The potential of VOM could be clearly mapped from endocardium using a QDM catheter. Both the accumulated operation time (p=0.032) and ablation time (p<0.001) were significantly shorter in the QDM group compared to the STSF group. QDM group achieved more conduction blocks of MI after a single endocardial line ablation (71.9% vs. 36.1%, p=0.017) with fewer ablation points (p<0.001) compared to the STSF group. The block rate of the MI after endocardial ablation alone was also higher in the QDM group than in the STSF group (90.6% vs. 69.4%; P=0.019), which avoided epicardial ablation. Even if epicardial ablation is necessary, the number of ablation points on the epicardial surface in the QDM group would be fewer than in the STSF group (p<0.001). Conclusions The QDM catheter can be used to map the potential of VOM from endocardium, thereby facilitating precise endocardial mitral isthmus linear ablation. The modified stepwise approach effectively reduces the number of endocardial ablation points and the likelihood of requiring epicardial ablation. Persistent atrial fibrillation QDOT MICRO catheter Mitral isthmus Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 What is new? We first used the QDOT MICRO (QDM) catheter to record the potential from the vein of Marshall (VOM) on the surface of the endocardium, guiding the endocardial ablation of MI. The biopotential recorded by the QDM catheter around MI included a higher sharp potential originating from the left atrium (LA) and a lower sharp potential originating from the VOM. The modified stepwise method guided by the QDM catheter for MI block was more effective and associated with fewer ablation points and shorter ablation time for the MI block than the stepwise method previously reported by us. Introduction Pulmonary vein isolation (PVI) has become the cornerstone of atrial fibrillation (AF) ablation, but it is not enough to maintain sinus rhythm for persistent atrial fibrillation (PeAF) [ 1 , 2 ]. Additional linear ablation beyond PVI, originating from the Cox-Maze surgical technique, is recommended to enhance the success of the ablation. Recently, authoritative journals have reported that the PVI plus linear ablation strategy is superior to PVI alone for patients with PeAF, especially for those facilitated by ethanol infusion of the vein of Marshall (EI-VOM) [ 3 – 5 ]. Mitral isthmus (MI) ablation is a key component and the most difficult step to achieve bidirectional block in the linear strategy due to its anatomical structure [ 6 ]. The success rates of MI block have been reported to be variable in different studies, and the high block rate always involved extensive endocardial ablation and epicardial ablation [ 7 – 9 ]. The imprecise ablation strategy increased the operational difficulty and risk. Our previous study introduced an efficient stepwise strategy for MI block with a high block rate;however, the procedure also requires two lines of endocardial ablation and epicardial ablation in more than 20% of cases [ 7 ]. A previous study reported that the potential of the vein of Marshall (VOM) could be recorded by a special mapping catheter [ 10 ]. The novel QDOT MICRO (QDM) catheter, with three microelectrodes inserted at the top of the catheter, was used to provide high-resolution intracardiac mapping and enhance the ability to precisely detect conduction gaps [ 11 ]. Therefore, the potentials originating from the Marshall ligament may be recorded from the endocardium using the QDM catheter, which can facilitate precise endocardial ablation. This study aimed to take advantage of the QDM catheter, recording potentials from VOM on the endocardial surface, to formulate the endocardial ablation line precisely, thereby increasing the success rate of MI block from the endocardium and reducing the possibility of ablation from the epicardium. Methods Study population and study design This study was a prospective, single-center, open-label, randomized study conducted at Henan Provincial People’s hospital. We enrolled 73 consecutive patients (aged 18 to 75 years) with PeAF for more than 1 year who underwent first-time catheter ablation in our hospital between October 3, 2024, and February 28, 2025. The patients were randomly categorized into the STSF ablation catheter (Biosense Webster, Irvine, USA) group (n = 37) using the stepwise method we proposed before and into the QDM catheter group (n = 36) using the modified stepwise method for MI ablation (Supplement Fig. 1 ) [ 8 ]. The numerical table method was used for randomization. Patients with previous cardiac surgery, left atrial diameter more than 55 mm, or left ventricular ejection fraction (LVEF) less than 35% were excluded. The trial was approved by the Institution Review Board of our hospital. All the included patients provided written informed consent. Preoperative preparation and intra-procedural setting All the included patients underwent cardiac contrast-enhanced computed tomography or transesophageal echocardiography to rule out left atrial thrombosis. Antiarrhythmic drugs (amiodarone or others) were discontinued for a minimum of five half-lives before the ablation procedure. All the procedures were performed under general anesthesia. A steerable decapolar catheter (DecaNAV; Biosense Webster, Irvine, USA) was used to construct the matrix and advanced into the CS. Then, the CS was mapped using the DecaNAV catheter. The first transseptal puncture was performed under the guidance of X-ray and intracardiac echocardiography. A Pentaray catheter (Biosense Webster, Irvine, USA) was inserted into the left atrium (LA) using the Swartz sheath (Abbott, Chicago, USA), and electro-anatomical maps of the pulmonary veins (PVs) and LA were constructed. The ablation strategy of pulmonary vein isolation (PVI) combined with linear ablation was chosen. Linear ablation involved MI, cavotricuspid isthmus, LA roof, and bottom lines. The posterior wall of PVI and roof line ablation were performed using the very high-power short-duration (vHPSD) model of the QDM catheter in the QDM group. The other positions' ablation in the QDM group and the whole ablation procedure in the STSF group were performed using the conventional-power temperature-controlled (CPTC) model. The ablation procedure for MI followed the two workflows below according to different groups. Workflow of the stepwise ablation method The detailed steps of the stepwise method for MI block using the STSF ablation catheter were according to the article we published previously [ 8 ]. Briefly, the four steps include EI-VOM, “V-shape” endocardial linear ablation, earliest activation sites (EASs) near the ablation line on the endocardium, and key ablation targets (KAT) in coronary sinus (CS). Workflow of the modified stepwise ablation method The steps of the modified stepwise strategy for blocking MI according to the potentials from Marshall on the endocardial surface recorded by the DQM catheter were as follows: Step 1. Mapping the potentials of VOM After constructing the PVs and LA, sinus rhythm (SR) was restored by transthoracic cardioversion. A 6F Judkins R4.0 guiding catheter was cannulated inside the Swartz sheath to perform CS venography and identify the ostium of VOM. Then, the DQM catheter was sent to the ostium of VOM to record the local potential and mark the position of the VOM ostium on the 3D model of CS precisely. After that, the QDM catheter was sent to the left atrium to detect VOM potentials around the MI area from the endocardial surface, referencing the course of VOM which was guided by CS venography. The site with double potential was marked by special color dots on the 3D model of LA (Fig. 1 ). The course formed by these special dots would be used to guide operators in formulating the first ablation line on endocardial surface. Step 2: EI-VOM EI-VOM was performed according to a previously published protocol [ 8 ]. An over-the-wire angioplasty balloon (Emerge 1.5–2.5 mm x 6–8 mm; Boston Scientific) preloaded with a guidewire was advanced into the proximal VOM, and 5–8 ml of 98% ethanol was injected into the VOM for 1 min. After conducting EI-VOM, the QDM catheter was relocated again to the sites marked in step 1 to detect the local potential (Fig. 2 ), and voltage mapping of LA for the second time was performed to locate the low voltage region of MI and the ethanol-induced scar (Supplement Fig. 2 ). If the endpoint of bidirectional block was not achieved after EI-VOM, we proceeded to the next step. Step 3: Endocardial ablation according to the guidance of bipotential recorded by QDM catheter The course of the first ablation line was infinitely close to the line formulated in step 1 according to the double potentials. The ablation points that change the sequence of CS temporarily or permanently and/or prolong the conduction time during ablation were marked and designated as key ablation targets (KATs) (Fig. 3 ) [ 8 ]. The reinforced ablation of KATs was performed. If MI block wasn’t fulfilled, the sequences of potentials on the QDM and CS at the same level were compared to verify whether the MI had been blocked from the endocardium. If the potential on the endocardium was earlier, the second ablation line of “V-sharp” and the ablation of earliest activation sites (EASs) around the two “V-shape” ablation lines were performed. If the block still hadn’t been achieved, step 4 would be processed. Step 4: Precise epicardial ablation The QDM catheter was inserted into the CS to perform precise epicardial ablation. Firstly, ablation around the VOM ostium was performed. Secondly, the anatomically corresponding sites of KATs on the epicardial side were ablated. If the block was not achieved, the ablation scale would be expanded appropriately in the CS (Fig. 4 ). If the MI block was achieved in step 4, it would be verified again after 20 minutes to confirm the continued existence of the bidirectional MI block. If the endpoint was not reached, the procedure was terminated and the MI block was considered a failure. Definition of MI bidirectional block Conduction block of MI was assessed by the activation sequence along the CS catheter and the ablation catheter. The conduction block was characterized as an activation detour when pacing on one side of the ablation line. The endpoint of the MI ablation was the achievement of a bidirectional block. If the Pentaray catheter was used for LAA pacing, proximal-to-distal activation on the CS catheter was considered a unidirectional block. When the QDM catheter was located on the high lateral side of the ablation lines for recording potential sequences and the CS was used for pacing, distal-to-proximal activation of QDM represented a bidirectional block of MI. Complications related to this procedure were recorded. Furthermore, we calculated the block rate and operation time for each step. Statistical analysis Statistical analyses were performed using the SPSS 25.0 software (SPSS Inc., Chicago, USA). For continuous variables, normally distributed data were expressed as the mean ± standard deviation (SD) and non-normally distributed data were expressed as median [interquartile range (IQR)]. The dichotomous variables were expressed as n (%). The normality of data distribution was tested using the Shapiro-Wilk test. Parametric tests (Student’s t-test) or non-parametric tests (Mann-Whitney U test) were used for comparing the continuous variables. Categorical variables were compared using the X 2 test or Fisher’s exact test. Two-sided P-values were reported and the significance level was set at ≤ 0.05. Results Baseline characteristics of patients The basic characteristics between the two groups did not show any significant statistical differences (Table 1 ). Table 1 Demographic characteristics of the PeAF patients Characteristics STSF group N = 36 QDM group N = 32 P value Age in y, mean (SD) 62.1 ± 23.2 56.9 ± 13.2 0.448 Male, n (%) 23 (63.9) 18 (56.3) 0.413 BMI (kg/m 2 ) 25.8 ± 4.6 25.9 ± 2.6 0.357 Duration of AF (months) 28.6 ± 14.9 24.2 ± 15.8 0.544 Risk factors, n (%) Hypertension 21 (58.3) 20 (62.5) 0.726 Diabetes 14 (38.9) 14 (43.8) 0.684 Strock-TIA 7 (19.4) 5 (15.6) 0.680 Coronary heart disease 4 (11.1) 6 (18.8) 0.375 Congestive heart failure 9 (25.0) 3 (9.4) 0.092 Antiarrhythmic drugs, n (%) Amiodarone 15 (41.7) 15 (46.9) 0.666 Β-block 15 (41.7) 16 (50.0) 0.491 NYHA functional Class ≥ 2, n (%) 4 (11.1) 4 (11.8) 0.859 CHA2DS2-VASC Scores 2.08 ± 1.3 2.03 ± 1.3 0.472 Left atrial diameter (mm) 46.5 ± 5.3 45.3 ± 5.9 0.568 Left atrial volume (mL) 156.3 ± 28.0 161.6 ± 28.5 0.996 Left ventricular ejection fraction (%) 52.7 ± 3.5 52.0 ± 4.7 0.102 AF: atrial fibrillation; BMI: Body Mass Index; CHF: congestive heart failure; TIA: transient ischemic attack; CHA2DS2-VASc: Congestive heart failure, Hypertension, Age ≥ 75 years (doubled), Diabetes mellitus, Stroke/transient ischemic attack/thromboembolism (doubled), Vascular disease (prior myocardial infarction, peripheral artery disease, or aortic plaque), Age 65 to 74 years, Sex Category (female). The characteristics of potential from Marshall Five points were selected for analysis from proximal to distal along the curve formulated in step 1 (Supplement Fig. 3 ). The amplitudes, durations, and distances of the two potentials of the bipotential recorded in step 1 were analyzed separately. The ahead potential of the double potential was deemed to be from the left atrium (A wave) and the latter one was deemed to be from Marshall (M wave). The amplitude of the M wave was lower compared to that of the A wave (0.84 ± 0.134 vs 0.32 ± 0.046, p < 0.001), with a longer duration (18.41 ± 1.09, P = 0.019). The distance between the A wave and the M wave has an increasing tendency from the proximal to the distal site of the curve we mapped in step 1 (Fig. 5 ). Comparison of procedure parameters between the two groups The procedural parameters were compared between the two groups (Table 2 ). Both the total procedure time (p = 0.032) and total ablation time (p < 0.001) were significantly shorter in the QDM group than in the STSF group. Compared to the STSF group, the total mapping time was longer in the QDM group (P < 0.001), while the radiofrequency times were significantly shorter for ablating PVs, conducting roof line, and MI (p < 0.001). The total fluoroscopy time was not statistically different between the two groups. Table 2 Comparison of procedure parameters between STSF and QDM Parameters STSF group N = 36 QDM group N = 32 P value Total procedure time (min) 201 (165, 226) 176.5 (157.5, 223) 0.032 Total ablation time (min) 100 (87, 114) 85.5 (66, 112) <0.001 Total mapping time (min) 14 (11, 17) 20.5 (15.5, 23) <0.001 Total mapping time for potential from VOM (min) - 8 (7, 11) - Total fluoroscopy time (min) 15 (11, 18.8) 14 (16, 19) 0.092 Total RF application time for ablating PVs (min) 45 (43, 55) 37 (32, 43) <0.001 Total RF application time for ablating Roof Line (min) 7 (6, 9) 4 (4, 5) <0.001 Total RF application time for MI (min) 23 (17, 25) 12.5 (9, 20) <0.001 VOM, vein of Marshall; PVs, pulmonary veins; RF, radiofrequency; MI, mitral isthmus. The operative time and effects of each step in both groups he median operation time of step 1 in the QDM group was 4 minutes. There were no differences in the operation time of EI-VOM between the two groups, and only 1 patient in the STSF group achieved conduction block of MI after that. Fewer patients in the QDM group required “V-shaped” and EASs ablation than those in the STSF group. Conduction block of MI was achieved in 71.9% of patients in the QDM group after a single line ablation, which was more than that in the STSF group (P = 0.017). Furthermore, with a shorter endocardial ablation time, the total number of ablation points was significantly lower in the QDM group compared to those in the STSF group (P < 0.001). Most importantly, after step 3, the QDM group exhibited a higher conduction block rate of MI than that in the STSF group (90.6% vs. 69.4%; P = 0.019). In step 4, the total number of ablation points with shorter ablation time (P < 0.001) was fewer in the QDM group than those in the STSF group (P < 0.001). Besides, the cumulative operation time was significantly shorter in the QDM group than that in the STSF group after step 4 (P = 0.021). Details of the comparison were shown in Table 3 and Supplement Fig. 4 . Table 3 Comparison of the time and effects of different steps in STSF and QDM STSF group N = 36 QDM group N = 32 P value Step 1: Outline the curve of VOM from the endocardial side Operation time (min) - 4 (3, 5) - Step 2: EI-VOM Operation time (min) 14 (12, 15) 14 (12, 15) 0.764 Accumulated operation time (min) 13.5 (12, 15) 18 (16, 19) <0.001 Conduction block of MI 1 (2.8) 0 (0) - Step 3: Endocardial ablation One line of “V sharp,” n (%) 13 (36.1) 23 (71.9) 0.017 Ablation after EASs mapping, n (%) 14 (38.9) 5 (5.6) 0.033 Total ablation points 19 (17.0, 21.8) 14 (12,16) <0.001 Operation time (min) 16 (15, 19) 13 (11,16) <0.001 Accumulated operation time (min) 30 (27.2, 33) 30 (27,33) 0.921 Conduction block of MI, n (%) 25 (69.4) 29 (90.6) 0.031 Step 4: Epicardial ablation Total ablation points 10 (6.3, 12.8) 4.5 (0, 6) <0.001 Operation time (min) 8 (7, 10) 5 (4, 6) <0.001 Accumulated operation time (min) 36 (30.5, 40.8) 31.5 (28.0, 36.8) 0.021 Conduction block of MI, n (%) 34 (94.4) 31 (96.8) 0.626 VOM: vein of Marshall; EI-VOM: ethanol infusion of the vein of Marshall; MI: mitral isthmus; operation time is expressed in minutes; and total number of ablation points is expressed as median (IQR); conduction block of MI, one line of V sharp, and ablation after EASs mapping were expressed by n (%); IQR: interquartile range; EASs: earliest activation sites. Complications Only 4 patients experienced complications in this study. No patients suffered fatal complications. Two patients in the STSF group and one patient in the QDM group developed pericardial effusion but did not need pericardiocentesis. In the QDM group, one patient developed a hematoma due to femoral venous puncture. Discussion The present study used the QDOT micro catheter to facilitate MI ablation in patients with PeAF. Furthermore, we modified the stepwise method for MI block proposed previously [ 7 ]. Our main findings were as follows: (1) VOM potential could be mapped around MI from the endocardial surface using the QDOT micro catheter. These potentials characterized by bipotential with a higher sharp potential from LA and a lower sharp potential from VOM (Fig. 2 ). (2) With fewer ablation points, the modified stepwise protocol increases the incidence of MI block after a single endocardial ablation line compared to the stepwise strategy. (3) The rate of conduction block of MI without epicardial ablation was higher in the QDM group than in the STSF group. Additional linear ablation beyond PVI was recommended to reinforce the maintenance of sinus rhythm after AF ablation [ 3 – 5 ]. However, the strategy has not been widely recognized and used due to the technical challenges. It was reported that incomplete lesions created anatomical substrates and could bring additional risks of atrial tachyarrhythmias [ 12 ]. Mitral isthmus (MI) ablation is a key component and the most difficult step to achieve bidirectional block in a linear strategy due to its anatomical structure [ 6 ]. The advent of new technologies and tools has increased the possibility of achieving MI bidirectional block, while variable block rates of MI are still reported in different studies [ 7 – 9 ]. The ligament of Marshall (LOM), which contains cardiomyocytes, adipose tissue, fibrous tissue, small blood vessels, and nerve tissue, lies on the epicardial surface of the MI area and increases its difficulty of ablation [ 13 , 14 ]. EI-VOM was reported to improve the success rate of MI block and AF ablation [ 3 ]. We have also reported a novel stepwise catheter ablation method for MI that included EI-VOM, V-shape ablation from the endocardium, and ablation of KATs from the epicardium, obtaining a high bidirectional block rate of 98.3% [ 7 ]. However, those methods involved extensive endocardial and epicardial ablation in the procedure [ 7 – 9 ]. The imprecise ablation strategy increased the operational difficulty and risk. Hwang et al. reported that the VOM potential could be recorded by an electrophysiological catheter into the VOM [ 10 ]; however, the VOM potential was recorded from the epicardium. The QDM catheter is a novel catheter for very high power-short duration (vHPSD) ablation. It contains 3 micro-electrodes (0.086 mm²) located at the tip of the electrode at an angle of 60°. The clinical feasibility and safety of MI ablations using the QDM catheter have been demonstrated by previous clinical studies [ 15 , 16 ]. Dello Russo et al. demonstrated that microelectrode mapping using the QDM catheter revealed higher amplitude, longer duration, and more fractionated electrograms, thereby identifying potential pathology in suspected regions more effectively than standard bipolar electrode mapping [ 17 ]. Therefore, the QDM catheter may be able to record the VOM potential from the endocardium and facilitate precise endocardial ablation. In this study, we used the precise mapping capability of the embedded micro-electrodes in the QDM catheter to record the VOM potential from the endocardium, along which the endocardial ablation line was performed precisely. The bipotential recorded by the QDM catheter from the surface of the endocardium includes a higher sharp potential from LA and a lower sharp potential from VOM. We speculate that the sites on the endocardial surface where the VOM potential can be recorded likely correspond to the endocardial terminations of myocardial bundles connecting the endocardium and epicardium in the region surrounding the mitral isthmus. Therefore, the endocardial ablation line guided by the VOM potential recorded via the QDOT catheter is likely to maximize the likelihood of achieving conduction block of MI from the endocardial surface. Our research results thoroughly confirmed the above hypothesis. The results found that the modified stepwise method with the guidance of QDOT MICRO catheter increased the incidence of MI block after a single endocardial ablation line with fewer ablation lesions, thereby avoiding further epicardial ablation. Limitation Several important limitations of this trial warrant mention. First, this study is a single-center, randomized, controlled study with a relatively small sample size. Subsequently, the sample size needs to be expanded and a multi-center randomized controlled study should be conducted. Secondly, the present work has not specifically evaluated the long-term outcomes. Our research group followed all patients in our study, and the follow-up results will be published in future studies, providing insights into the short- and long-term prognosis. Conclusions QDOT micro catheter can be used to map the potential of VOM from the endocardium, which facilitates guiding the endocardial MI linear ablation. The technique is able to reduce the endocardial ablation points and the chance of epicardial ablation with comparable complications. Declarations Ethics approval and consent to participate ： The study was approved by the ethics committee of Henan provincial people’s Hospital (permission no: 2021092) and was conducted in accordance with the Helsinki Declaration. All patients supplied their signed, informed consent prior to any operations. Consent for publication: Not Applicable. Data availability statement The data that support the findings of this study are available request from the corresponding author, Shujuan Dong. Conflict of interest: The authors declare that they have no conflict of interest. Funding Project of Key Science-Technology Foundation of Henan Province (1221023100). Author’s contribution: Jingchao Li and Xing Wang wrote the main manuscripts text. Luqian Cui conducted the statistical analysis and prepared table 1-3. Qianqian Feng and Huihui Song performed the operations.Cong Ding,Hailan Wang and Chaoyu Zhao collected the original and conducted radom. Haijia Yu propared the figures in the article. Shujuan Dong and Yingjie Chu designed the research and conducted the quality control of the study. All authors reviewed the manuscript. Clinical Trial Number: NCT06145906(ClinicalTrial.gov) Acknowledgements The authors sincerely thank our clinical specialists, Mr. Liujie Li and Miss Yingrong Xin from Zhengzhou University and Mr. Changyi Yang and Jinlong Li from Biosense Webster, who were very helpful during the ablation procedure and in the collection of CARTO backup data. References Van Gelder, IC, Rienstra, M, Bunting, KV, et al. 2024 ESC guidelines for the management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS). Eur Heart J. 2024; 45 (36): 3314-3414. Joglar, JA, Chung, MK, Armbruster, AL, et al. 2023 ACC/AHA/ACCP/HRS guideline for the diagnosis and management of atrial fibrillation: a report of the American College of Cardiology/American Heart Association Joint Committee on clinical practice guidelines. Circulation. 2023; 149 (1): e1-e156. Valderrábano, M, Peterson, LE, Swarup, V, et al. Effect of catheter ablation with vein of marshall ethanol infusion vs catheter ablation alone on persistent atrial fibrillation: the VENUS randomized clinical trial. JAMA. 2020; 324 (16): 1620-1628. Sang, C, Liu, Q, Lai, Y, et al. Pulmonary vein isolation with optimized linear ablation vs pulmonary vein isolation alone for persistent AF: the PROMPT-AF randomized clinical trial. JAMA. 2025; 333 (5): 381-389. Derval, N, Tixier, R, Duchateau, J, et al. Marshall-Plan Ablation Strategy Versus Pulmonary Vein Isolation in Persistent AF: A Randomized Controlled Trial. Circ Arrhythm Electrophysiol. 2025; 18 (5): e013427. Becker, AE. Left atrial isthmus: anatomic aspects relevant for linear catheter ablation procedures in humans. J Cardiovasc Electr. 2004; 15 (7): 809-812. Li, J, Cui, S, Song, H, et al. A novel stepwise catheter ablation method of the mitral isthmus for persistent atrial fibrillation: efficacy and reproducibility. BMC Cardiovasc Disord. 2023; 23 (1): 466. Li, X, Li, M, Zhang, Y, et al. Simplified stepwise anatomical ablation strategy for mitral isthmus: efficacy, efficiency, safety, and outcome. EUROPACE. 2023; 25 (2): 610-618. He, B, Yu, W, Li, Y, et al. Acute mitral isthmus block in patients undergoing catheter ablation for atrial fibrillation: efficacy and safety of a systematic stepwise approach. J Interv Card Electrophysiol. 2025; 68 (8): 1647-1659. Hwang, C, Wu, TJ, Doshi, RN, et al. Vein of marshall cannulation for the analysis of electrical activity in patients with focal atrial fibrillation. Circulation. 2000; 101 (13): 1503-1505. Osorio, J, Hussein, AA, Delaughter, MC, et al. Very high-power short-duration, temperature-controlled radiofrequency ablation in paroxysmal atrial fibrillation: the prospective multicenter Q-FFICIENCY trial. JACC: Clin Electrophysiol. 2023; 9 (4): 468-480. Sawhney, N, Anand, K, Robertson, CE, et al. Recovery of mitral isthmus conduction leads to the development of macro-reentrant tachycardia after left atrial linear ablation for atrial fibrillation. Circ Arrhythm Electrophysiol. 2011; 4 (6): 832-837. VI. On the development of the great anterior veins in man and mammalia; including an account of certain remnants of fætal structure found in the adult, a comparative view of these great veins the different mammalia, and an analysis of their occasional peculiarities in the human subject Philos Trans R Soc Lond. 1997; 140 133-170. Chugh, A, Gurm, HS, Krishnasamy, K, et al. Spectrum of atrial arrhythmias using the ligament of Marshall in patients with atrial fibrillation. Heart Rhythm. 2017; 15 (1): 17-24. Reddy, VY, Grimaldi, M, De Potter, T, et al. Pulmonary Vein Isolation With Very High Power, Short Duration, Temperature-Controlled Lesions: The QDOT-FAST Trial. JACC Clin Electrophysiol. 2019; 5 (7): 778-786. Osorio, J, Hussein, AA, Delaughter, MC, et al. Very high-power short-duration, temperature-controlled radiofrequency ablation in paroxysmal atrial fibrillation: the prospective multicenter Q-FFICIENCY trial. JACC: Clin Electrophysiol. 2023; 9 (4): 468-480. Dello Russo, A, Compagnucci, P, Bergonti, M, et al. Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: a dual-center experience. J Cardiovasc Electr. 2023; 34 (5): 1216-1227. Additional Declarations No competing interests reported. Supplementary Files Supplementfigures.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8308466","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":558991211,"identity":"e9446139-f711-438a-bd9e-ce0be5db328b","order_by":0,"name":"Jingchao Li","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jingchao","middleName":"","lastName":"Li","suffix":""},{"id":558991212,"identity":"577270e6-3d8e-4f65-a54f-8b9c115ad174","order_by":1,"name":"Chaoyu Zhao","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chaoyu","middleName":"","lastName":"Zhao","suffix":""},{"id":558991213,"identity":"69ec1963-0806-4606-ac92-2c97afbd9f88","order_by":2,"name":"Luqian Cui","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Luqian","middleName":"","lastName":"Cui","suffix":""},{"id":558991214,"identity":"92628e91-4ea7-48af-8a6c-5da120e2d301","order_by":3,"name":"Xin Wang","email":"","orcid":"","institution":"Henan Provincial Chest Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xin","middleName":"","lastName":"Wang","suffix":""},{"id":558991215,"identity":"37d6cad0-b58e-40f3-99f5-ab2ff31821f9","order_by":4,"name":"Qianqian Feng","email":"","orcid":"","institution":"Zhoukou Central Hospital","correspondingAuthor":false,"prefix":"","firstName":"Qianqian","middleName":"","lastName":"Feng","suffix":""},{"id":558991218,"identity":"5f6019b6-4d56-48e5-aa24-59561e915eeb","order_by":5,"name":"Huihui Song","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Huihui","middleName":"","lastName":"Song","suffix":""},{"id":558991219,"identity":"4e44eb5b-d8be-4d69-8c21-4df90917fc15","order_by":6,"name":"Cong Ding","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Cong","middleName":"","lastName":"Ding","suffix":""},{"id":558991220,"identity":"fb5f723c-243b-4598-ad66-006cfc7f52b6","order_by":7,"name":"Hailan Wang","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Hailan","middleName":"","lastName":"Wang","suffix":""},{"id":558991221,"identity":"c2839572-20c8-4ecd-960f-1018bbca9305","order_by":8,"name":"Haijia Yu","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Haijia","middleName":"","lastName":"Yu","suffix":""},{"id":558991222,"identity":"32e420e5-c64d-4966-923b-4f678af1dcd8","order_by":9,"name":"Yingjie Chu","email":"","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yingjie","middleName":"","lastName":"Chu","suffix":""},{"id":558991223,"identity":"356338f7-6362-437c-aa36-ad5c26bd351a","order_by":10,"name":"Shujuan Dong","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuUlEQVRIiWNgGAWjYBACAxDBw8Amx8befoA0LcZ8PGcSSNLCkDhPwsGAOC3m0u3PJN784Utvk2BIYPhRsY2wFss5Z8wk57ax5bZJNx5g7DlzmwiH3chhk+ZtAGqROZDAzNhGlJb0Z9I8f9jS2SQSDIjVkmAmzcPGlkCKlhxjS6BfDNuAgXyQSL+kP7zx5s8xefn29oMPflQQoQUIWCQYGI6BWQeIUg8EzB8YGGqIVTwKRsEoGAUjEQAAUlQ6KlMuHSoAAAAASUVORK5CYII=","orcid":"","institution":"Henan Provincial People's Hospital","correspondingAuthor":true,"prefix":"","firstName":"Shujuan","middleName":"","lastName":"Dong","suffix":""}],"badges":[],"createdAt":"2025-12-08 13:53:57","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8308466/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8308466/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":98218467,"identity":"e146275b-b5c7-4892-9260-1464c0377224","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":46136,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.docx","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/757253722521aa50a5de9f99.docx"},{"id":98218470,"identity":"b9273ddb-5590-4688-944d-60453cb79036","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":19004,"visible":true,"origin":"","legend":"","description":"","filename":"table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/e72bfc5bcdc6e6ba40417b24.docx"},{"id":98432500,"identity":"692141c1-e657-462b-afb7-a402338b9e68","added_by":"auto","created_at":"2025-12-17 16:49:37","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":17489,"visible":true,"origin":"","legend":"","description":"","filename":"table2.docx","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/f1935816daf59b33eeb24610.docx"},{"id":98432302,"identity":"cb45a865-2c80-4234-8d8c-39124617e7d0","added_by":"auto","created_at":"2025-12-17 16:49:21","extension":"docx","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":18842,"visible":true,"origin":"","legend":"","description":"","filename":"table3.docx","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/74bfb163b9384321d3ce6db1.docx"},{"id":98218477,"identity":"40024ee2-76db-47f5-bc58-97326f708d65","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"json","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11792,"visible":true,"origin":"","legend":"","description":"","filename":"1a7dbb8b9e4e4c1c9d6ee4a724fea42f.json","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/5ee75388ee179b72bb05023e.json"},{"id":98218483,"identity":"c539a6ae-7ed3-495d-aeb3-b26b7b40a06e","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"docx","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1163155,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementfigures.docx","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/989db5fe092f353458f1e1d4.docx"},{"id":98432539,"identity":"1fdfc2cf-e43c-49ed-96b6-6b9570125006","added_by":"auto","created_at":"2025-12-17 16:49:40","extension":"xml","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":78148,"visible":true,"origin":"","legend":"","description":"","filename":"1a7dbb8b9e4e4c1c9d6ee4a724fea42f1enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/cc9d95fff39ddf8998238e7e.xml"},{"id":98218478,"identity":"7485c63d-dba1-4c30-9ed7-492dc04f479b","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":442349,"visible":true,"origin":"","legend":"","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/389bf15d6e37cee9cb22b3b1.png"},{"id":98218473,"identity":"7a096bef-a944-4bf1-9351-b5c466d8385f","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1179034,"visible":true,"origin":"","legend":"","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/4e8e304fdb331c4a00c00d52.png"},{"id":98218487,"identity":"0c108846-0dee-4a41-84dc-a1a90505bcd5","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1618744,"visible":true,"origin":"","legend":"","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/9e41a668426c79db8d6cc74f.png"},{"id":98218479,"identity":"ec5d542b-1dfd-4382-9ffd-e6c9636c99d4","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1226400,"visible":true,"origin":"","legend":"","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/a2b5517bdd16bf601633dd97.png"},{"id":98433583,"identity":"f8b50410-eae9-4b99-8012-b15748cfb7ae","added_by":"auto","created_at":"2025-12-17 16:50:55","extension":"png","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":98086,"visible":true,"origin":"","legend":"","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/e1631b45e98bbc2d9665e1ff.png"},{"id":98433763,"identity":"e7082870-5f41-4cc7-a73f-40f489f48e0d","added_by":"auto","created_at":"2025-12-17 16:51:06","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":47578,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFigure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/a8a5063b7b40283b6fe7283e.png"},{"id":98431768,"identity":"26627c97-69fb-42c4-bbe6-97e9fc05e5ad","added_by":"auto","created_at":"2025-12-17 16:48:18","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":126225,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFigure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/2a38e351aace39b01c1f24ea.png"},{"id":98432589,"identity":"ebc0341c-2397-4ce4-96b5-d4401b964435","added_by":"auto","created_at":"2025-12-17 16:49:44","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":172102,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFigure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/fca3a66b7bcaa2088da6c6c9.png"},{"id":98218492,"identity":"98710dc5-c839-4917-9e4c-981cb5e37401","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":119864,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFigure4.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/cb1bfc872da257aa60e4405e.png"},{"id":98218488,"identity":"a6c705a8-4fcf-494c-9980-68564e2c9663","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":29251,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFigure5.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/96876c90639dcb5117c15047.png"},{"id":98433738,"identity":"5a0a9b21-84df-468c-b627-dee655041c3e","added_by":"auto","created_at":"2025-12-17 16:51:05","extension":"xml","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":76846,"visible":true,"origin":"","legend":"","description":"","filename":"1a7dbb8b9e4e4c1c9d6ee4a724fea42f1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/225643771ed33c7ab5d1b18e.xml"},{"id":98218490,"identity":"8c369a58-05ec-4a05-af84-f33fa9d04c55","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"html","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":82533,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/c40ca517dee36b40e329f838.html"},{"id":98434076,"identity":"10a8825f-c831-446b-92df-744dec45455d","added_by":"auto","created_at":"2025-12-17 16:51:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":105967,"visible":true,"origin":"","legend":"\u003cp\u003eMapping the potentials of VOM. The trend of these cyan dots could reflect the curve of VOM from the endocardial side. The red arrow points to the special potential (double potentials). The green model is the CS construction. The big blue dot is the ostium of VOM, marked from the epicardium.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/a1c6b8190f00d96b330b864d.png"},{"id":98218468,"identity":"cf1ce617-2323-413f-8208-ff53b12eafc4","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":265985,"visible":true,"origin":"","legend":"\u003cp\u003eSecond mapping of VOM potentials. Little cyan dots represent the locations where potentials could be recorded from VOM before EV-VOM, little orange dots are areas where the DQM catheter was relocated after EV-VOM, and the local potentials (red arrows) were recorded by the microelectrodes on the tip of the DQM catheter. The green model is the CS construction. The big blue dot is the ostium of VOM, marked from the epicardium.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/868944a61a3c3b3fcbf561a1.png"},{"id":98433802,"identity":"fabe85ba-004c-4794-84a9-876a4f608c16","added_by":"auto","created_at":"2025-12-17 16:51:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":343692,"visible":true,"origin":"","legend":"\u003cp\u003eKey ablation targets. The yellow dot is the KAT in the endocardium on the lower line of the “V-shape.” The little cyan dots are locations where potentials could be recorded from VOM in step 1 by the DQM catheter. Pink dots are electrode marks of DecaNAV. The big blue dot is the ostium of VOM, marked from the epicardium. A: left lateral position. B: posterior anterior position.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/2cff6680170582446d614bec.png"},{"id":98431893,"identity":"a7e4f6d4-4ca8-4ac0-9a81-ae5870eeb6cd","added_by":"auto","created_at":"2025-12-17 16:48:34","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":242477,"visible":true,"origin":"","legend":"\u003cp\u003ePrecise epicardial ablation. The yellow dot is the KAT in the epicardium. The little cyan dots are locations where potentials could be recorded from VOM in step 1 by the DQM catheter. The green model is CS mapped by DecaNAV. The big blue dot is the ostium of VOM, marked from the epicardium. A: left lateral position. B: posterior anterior position.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/b35a35822cb6a8b89083dce1.png"},{"id":98218472,"identity":"32663af4-a12f-4a19-b596-0e1bd0dddef0","added_by":"auto","created_at":"2025-12-15 11:02:33","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":117354,"visible":true,"origin":"","legend":"\u003cp\u003eThe characteristics of the double potential mapped in step 1. A: The amplitude difference between the A wave and the M wave. B: The duration difference between the A wave and the M wave. C: The increasing tendency of the A-M distance from the proximal to distal part of the curve mapped in step 1. A wave: potential from the left atrium. M wave: potential from Marshall.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/70628bf61f58553a34d18ee5.png"},{"id":99309764,"identity":"a49f04a7-60c3-42fb-995b-b902058fb39f","added_by":"auto","created_at":"2025-12-31 16:11:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2051259,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/dfc10e28-ff72-40b6-aa04-7360de84a404.pdf"},{"id":98432252,"identity":"643492db-a97f-4ed4-b7f0-929759b038d4","added_by":"auto","created_at":"2025-12-17 16:49:18","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1163155,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementfigures.docx","url":"https://assets-eu.researchsquare.com/files/rs-8308466/v1/b74010ad54f9f39f083f1d8c.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Modified stepwise method with the guidance of QDOT MICRO catheter for mitral isthmus ablation in patients with persistent atrial fibrillation","fulltext":[{"header":"What is new?","content":"\u003cul\u003e\n \u003cli\u003eWe first used the QDOT MICRO (QDM) catheter to record the potential from the vein of Marshall (VOM) on the surface of the endocardium, guiding the endocardial ablation of MI.\u003c/li\u003e\n \u003cli\u003eThe biopotential recorded by the QDM catheter around MI included a higher sharp potential originating from the left atrium (LA) and a lower sharp potential originating from the VOM. The modified stepwise method guided by the QDM catheter for MI block was more effective and associated with fewer ablation points and shorter ablation time for the MI block than the stepwise method previously reported by us.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Introduction","content":"\u003cp\u003ePulmonary vein isolation (PVI) has become the cornerstone of atrial fibrillation (AF) ablation, but it is not enough to maintain sinus rhythm for persistent atrial fibrillation (PeAF) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Additional linear ablation beyond PVI, originating from the Cox-Maze surgical technique, is recommended to enhance the success of the ablation. Recently, authoritative journals have reported that the PVI plus linear ablation strategy is superior to PVI alone for patients with PeAF, especially for those facilitated by ethanol infusion of the vein of Marshall (EI-VOM) [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Mitral isthmus (MI) ablation is a key component and the most difficult step to achieve bidirectional block in the linear strategy due to its anatomical structure [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The success rates of MI block have been reported to be variable in different studies, and the high block rate always involved extensive endocardial ablation and epicardial ablation [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The imprecise ablation strategy increased the operational difficulty and risk. Our previous study introduced an efficient stepwise strategy for MI block with a high block rate;however, the procedure also requires two lines of endocardial ablation and epicardial ablation in more than 20% of cases [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eA previous study reported that the potential of the vein of Marshall (VOM) could be recorded by a special mapping catheter [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The novel QDOT MICRO (QDM) catheter, with three microelectrodes inserted at the top of the catheter, was used to provide high-resolution intracardiac mapping and enhance the ability to precisely detect conduction gaps [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Therefore, the potentials originating from the Marshall ligament may be recorded from the endocardium using the QDM catheter, which can facilitate precise endocardial ablation.\u003c/p\u003e\u003cp\u003eThis study aimed to take advantage of the QDM catheter, recording potentials from VOM on the endocardial surface, to formulate the endocardial ablation line precisely, thereby increasing the success rate of MI block from the endocardium and reducing the possibility of ablation from the epicardium.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy population and study design\u003c/h2\u003e\u003cp\u003eThis study was a prospective, single-center, open-label, randomized study conducted at Henan Provincial People\u0026rsquo;s hospital. We enrolled 73 consecutive patients (aged 18 to 75 years) with PeAF for more than 1 year who underwent first-time catheter ablation in our hospital between October 3, 2024, and February 28, 2025. The patients were randomly categorized into the STSF ablation catheter (Biosense Webster, Irvine, USA) group (n\u0026thinsp;=\u0026thinsp;37) using the stepwise method we proposed before and into the QDM catheter group (n\u0026thinsp;=\u0026thinsp;36) using the modified stepwise method for MI ablation (Supplement Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The numerical table method was used for randomization. Patients with previous cardiac surgery, left atrial diameter more than 55 mm, or left ventricular ejection fraction (LVEF) less than 35% were excluded. The trial was approved by the Institution Review Board of our hospital. All the included patients provided written informed consent.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003ePreoperative preparation and intra-procedural setting\u003c/h3\u003e\n\u003cp\u003eAll the included patients underwent cardiac contrast-enhanced computed tomography or transesophageal echocardiography to rule out left atrial thrombosis. Antiarrhythmic drugs (amiodarone or others) were discontinued for a minimum of five half-lives before the ablation procedure.\u003c/p\u003e\u003cp\u003eAll the procedures were performed under general anesthesia. A steerable decapolar catheter (DecaNAV; Biosense Webster, Irvine, USA) was used to construct the matrix and advanced into the CS. Then, the CS was mapped using the DecaNAV catheter. The first transseptal puncture was performed under the guidance of X-ray and intracardiac echocardiography. A Pentaray catheter (Biosense Webster, Irvine, USA) was inserted into the left atrium (LA) using the Swartz sheath (Abbott, Chicago, USA), and electro-anatomical maps of the pulmonary veins (PVs) and LA were constructed. The ablation strategy of pulmonary vein isolation (PVI) combined with linear ablation was chosen. Linear ablation involved MI, cavotricuspid isthmus, LA roof, and bottom lines. The posterior wall of PVI and roof line ablation were performed using the very high-power short-duration (vHPSD) model of the QDM catheter in the QDM group. The other positions' ablation in the QDM group and the whole ablation procedure in the STSF group were performed using the conventional-power temperature-controlled (CPTC) model. The ablation procedure for MI followed the two workflows below according to different groups.\u003c/p\u003e\n\u003ch3\u003eWorkflow of the stepwise ablation method\u003c/h3\u003e\n\u003cp\u003eThe detailed steps of the stepwise method for MI block using the STSF ablation catheter were according to the article we published previously [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Briefly, the four steps include EI-VOM, \u0026ldquo;V-shape\u0026rdquo; endocardial linear ablation, earliest activation sites (EASs) near the ablation line on the endocardium, and key ablation targets (KAT) in coronary sinus (CS).\u003c/p\u003e\n\u003ch3\u003eWorkflow of the modified stepwise ablation method\u003c/h3\u003e\n\u003cp\u003eThe steps of the modified stepwise strategy for blocking MI according to the potentials from Marshall on the endocardial surface recorded by the DQM catheter were as follows:\u003c/p\u003e\n\u003ch3\u003eStep 1. Mapping the potentials of VOM\u003c/h3\u003e\n\u003cp\u003eAfter constructing the PVs and LA, sinus rhythm (SR) was restored by transthoracic cardioversion. A 6F Judkins R4.0 guiding catheter was cannulated inside the Swartz sheath to perform CS venography and identify the ostium of VOM. Then, the DQM catheter was sent to the ostium of VOM to record the local potential and mark the position of the VOM ostium on the 3D model of CS precisely. After that, the QDM catheter was sent to the left atrium to detect VOM potentials around the MI area from the endocardial surface, referencing the course of VOM which was guided by CS venography. The site with double potential was marked by special color dots on the 3D model of LA (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The course formed by these special dots would be used to guide operators in formulating the first ablation line on endocardial surface.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eStep 2: EI-VOM\u003c/h2\u003e\u003cp\u003eEI-VOM was performed according to a previously published protocol [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. An over-the-wire angioplasty balloon (Emerge 1.5\u0026ndash;2.5 mm x 6\u0026ndash;8 mm; Boston Scientific) preloaded with a guidewire was advanced into the proximal VOM, and 5\u0026ndash;8 ml of 98% ethanol was injected into the VOM for 1 min. After conducting EI-VOM, the QDM catheter was relocated again to the sites marked in step 1 to detect the local potential (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), and voltage mapping of LA for the second time was performed to locate the low voltage region of MI and the ethanol-induced scar (Supplement Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIf the endpoint of bidirectional block was not achieved after EI-VOM, we proceeded to the next step.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eStep 3: Endocardial ablation according to the guidance of bipotential recorded by QDM catheter\u003c/h3\u003e\n\u003cp\u003eThe course of the first ablation line was infinitely close to the line formulated in step 1 according to the double potentials. The ablation points that change the sequence of CS temporarily or permanently and/or prolong the conduction time during ablation were marked and designated as key ablation targets (KATs) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The reinforced ablation of KATs was performed. If MI block wasn\u0026rsquo;t fulfilled, the sequences of potentials on the QDM and CS at the same level were compared to verify whether the MI had been blocked from the endocardium. If the potential on the endocardium was earlier, the second ablation line of \u0026ldquo;V-sharp\u0026rdquo; and the ablation of earliest activation sites (EASs) around the two \u0026ldquo;V-shape\u0026rdquo; ablation lines were performed. If the block still hadn\u0026rsquo;t been achieved, step 4 would be processed.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eStep 4: Precise epicardial ablation\u003c/h3\u003e\n\u003cp\u003eThe QDM catheter was inserted into the CS to perform precise epicardial ablation. Firstly, ablation around the VOM ostium was performed. Secondly, the anatomically corresponding sites of KATs on the epicardial side were ablated. If the block was not achieved, the ablation scale would be expanded appropriately in the CS (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIf the MI block was achieved in step 4, it would be verified again after 20 minutes to confirm the continued existence of the bidirectional MI block. If the endpoint was not reached, the procedure was terminated and the MI block was considered a failure.\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eDefinition of MI bidirectional block\u003c/h2\u003e\u003cp\u003eConduction block of MI was assessed by the activation sequence along the CS catheter and the ablation catheter. The conduction block was characterized as an activation detour when pacing on one side of the ablation line. The endpoint of the MI ablation was the achievement of a bidirectional block.\u003c/p\u003e\u003cp\u003eIf the Pentaray catheter was used for LAA pacing, proximal-to-distal activation on the CS catheter was considered a unidirectional block. When the QDM catheter was located on the high lateral side of the ablation lines for recording potential sequences and the CS was used for pacing, distal-to-proximal activation of QDM represented a bidirectional block of MI.\u003c/p\u003e\u003cp\u003eComplications related to this procedure were recorded. Furthermore, we calculated the block rate and operation time for each step.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eStatistical analyses were performed using the SPSS 25.0 software (SPSS Inc., Chicago, USA). For continuous variables, normally distributed data were expressed as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD) and non-normally distributed data were expressed as median [interquartile range (IQR)]. The dichotomous variables were expressed as n (%). The normality of data distribution was tested using the Shapiro-Wilk test. Parametric tests (Student\u0026rsquo;s t-test) or non-parametric tests (Mann-Whitney U test) were used for comparing the continuous variables. Categorical variables were compared using the X\u003csup\u003e2\u003c/sup\u003e test or Fisher\u0026rsquo;s exact test. Two-sided P-values were reported and the significance level was set at \u0026le;\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eBaseline characteristics of patients\u003c/h2\u003e\u003cp\u003eThe basic characteristics between the two groups did not show any significant statistical differences (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDemographic characteristics of the PeAF patients\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristics\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSTSF group\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;36\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eQDM group\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;32\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge in y, mean (SD)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e62.1\u0026thinsp;\u0026plusmn;\u0026thinsp;23.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e56.9\u0026thinsp;\u0026plusmn;\u0026thinsp;13.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.448\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23 (63.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (56.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.413\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.357\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDuration of AF (months)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e28.6\u0026thinsp;\u0026plusmn;\u0026thinsp;14.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.544\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRisk factors, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypertension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e21 (58.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20 (62.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.726\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (38.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14 (43.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.684\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStrock-TIA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (19.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (15.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.680\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCoronary heart disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (11.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6 (18.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.375\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCongestive heart failure\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9 (25.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (9.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.092\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAntiarrhythmic drugs, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAmiodarone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (41.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15 (46.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.666\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eΒ-block\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (41.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16 (50.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.491\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNYHA functional Class\u0026thinsp;\u0026ge;\u0026thinsp;2, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (11.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (11.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.859\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCHA2DS2-VASC Scores\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.08\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.03\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.472\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeft atrial diameter (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e46.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e45.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.568\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeft atrial volume (mL)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e156.3\u0026thinsp;\u0026plusmn;\u0026thinsp;28.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e161.6\u0026thinsp;\u0026plusmn;\u0026thinsp;28.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.996\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLeft ventricular ejection fraction (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e52.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e52.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.102\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eAF: atrial fibrillation; BMI: Body Mass Index; CHF: congestive heart failure; TIA: transient ischemic attack; CHA2DS2-VASc: Congestive heart failure, Hypertension, Age\u0026thinsp;\u0026ge;\u0026thinsp;75 years (doubled), Diabetes mellitus, Stroke/transient ischemic attack/thromboembolism (doubled), Vascular disease (prior myocardial infarction, peripheral artery disease, or aortic plaque), Age 65 to 74 years, Sex Category (female).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eThe characteristics of potential from Marshall\u003c/h2\u003e\u003cp\u003eFive points were selected for analysis from proximal to distal along the curve formulated in step 1 (Supplement Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The amplitudes, durations, and distances of the two potentials of the bipotential recorded in step 1 were analyzed separately. The ahead potential of the double potential was deemed to be from the left atrium (A wave) and the latter one was deemed to be from Marshall (M wave). The amplitude of the M wave was lower compared to that of the A wave (0.84\u0026thinsp;\u0026plusmn;\u0026thinsp;0.134 vs 0.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.046, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with a longer duration (18.41\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09, P\u0026thinsp;=\u0026thinsp;0.019). The distance between the A wave and the M wave has an increasing tendency from the proximal to the distal site of the curve we mapped in step 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003eComparison of procedure parameters between the two groups\u003c/h2\u003e\u003cp\u003eThe procedural parameters were compared between the two groups (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Both the total procedure time (p\u0026thinsp;=\u0026thinsp;0.032) and total ablation time (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) were significantly shorter in the QDM group than in the STSF group. Compared to the STSF group, the total mapping time was longer in the QDM group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while the radiofrequency times were significantly shorter for ablating PVs, conducting roof line, and MI (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The total fluoroscopy time was not statistically different between the two groups.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of procedure parameters between STSF and QDM\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameters\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSTSF group\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;36\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eQDM group\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;32\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal procedure time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e201 (165, 226)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e176.5 (157.5, 223)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.032\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal ablation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100 (87, 114)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e85.5 (66, 112)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal mapping time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (11, 17)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.5 (15.5, 23)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal mapping time for potential from VOM (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8 (7, 11)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal fluoroscopy time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (11, 18.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14 (16, 19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.092\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal RF application time for ablating PVs (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e45 (43, 55)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37 (32, 43)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal RF application time for ablating Roof Line (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (6, 9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (4, 5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal RF application time for MI (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23 (17, 25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.5 (9, 20)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eVOM, vein of Marshall; PVs, pulmonary veins; RF, radiofrequency; MI, mitral isthmus.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003eThe operative time and effects of each step in both groups\u003c/h2\u003e\u003cp\u003ehe median operation time of step 1 in the QDM group was 4 minutes. There were no differences in the operation time of EI-VOM between the two groups, and only 1 patient in the STSF group achieved conduction block of MI after that. Fewer patients in the QDM group required \u0026ldquo;V-shaped\u0026rdquo; and EASs ablation than those in the STSF group. Conduction block of MI was achieved in 71.9% of patients in the QDM group after a single line ablation, which was more than that in the STSF group (P\u0026thinsp;=\u0026thinsp;0.017). Furthermore, with a shorter endocardial ablation time, the total number of ablation points was significantly lower in the QDM group compared to those in the STSF group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Most importantly, after step 3, the QDM group exhibited a higher conduction block rate of MI than that in the STSF group (90.6% vs. 69.4%; P\u0026thinsp;=\u0026thinsp;0.019). In step 4, the total number of ablation points with shorter ablation time (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) was fewer in the QDM group than those in the STSF group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Besides, the cumulative operation time was significantly shorter in the QDM group than that in the STSF group after step 4 (P\u0026thinsp;=\u0026thinsp;0.021). Details of the comparison were shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Supplement Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of the time and effects of different steps in STSF and QDM\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSTSF group\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;36\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eQDM group\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;32\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStep 1: Outline the curve of VOM from the endocardial side\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (3, 5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStep 2: EI-VOM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (12, 15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14 (12, 15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.764\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAccumulated operation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13.5 (12, 15)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (16, 19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eConduction block of MI\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (2.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStep 3: Endocardial ablation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOne line of \u0026ldquo;V sharp,\u0026rdquo; n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13 (36.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23 (71.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.017\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAblation after EASs mapping, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (38.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (5.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.033\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal ablation points\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e19 (17.0, 21.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14 (12,16)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (15, 19)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e13 (11,16)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAccumulated operation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30 (27.2, 33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30 (27,33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.921\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eConduction block of MI, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25 (69.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e29 (90.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.031\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStep 4: Epicardial ablation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal ablation points\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003cp\u003e(6.3, 12.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003cp\u003e(0, 6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (7, 10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (4, 6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAccumulated operation time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e36\u003c/p\u003e\u003cp\u003e(30.5, 40.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.5\u003c/p\u003e\u003cp\u003e(28.0, 36.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.021\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eConduction block of MI, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e34 (94.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31 (96.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e0.626\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003eVOM: vein of Marshall; EI-VOM: ethanol infusion of the vein of Marshall; MI: mitral isthmus; operation time is expressed in minutes; and total number of ablation points is expressed as median (IQR); conduction block of MI, one line of V sharp, and ablation after EASs mapping were expressed by n (%); IQR: interquartile range; EASs: earliest activation sites.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003eComplications\u003c/h2\u003e\u003cp\u003eOnly 4 patients experienced complications in this study. No patients suffered fatal complications. Two patients in the STSF group and one patient in the QDM group developed pericardial effusion but did not need pericardiocentesis. In the QDM group, one patient developed a hematoma due to femoral venous puncture.\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study used the QDOT micro catheter to facilitate MI ablation in patients with PeAF. Furthermore, we modified the stepwise method for MI block proposed previously [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Our main findings were as follows: (1) VOM potential could be mapped around MI from the endocardial surface using the QDOT micro catheter. These potentials characterized by bipotential with a higher sharp potential from LA and a lower sharp potential from VOM (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). (2) With fewer ablation points, the modified stepwise protocol increases the incidence of MI block after a single endocardial ablation line compared to the stepwise strategy. (3) The rate of conduction block of MI without epicardial ablation was higher in the QDM group than in the STSF group.\u003c/p\u003e\u003cp\u003eAdditional linear ablation beyond PVI was recommended to reinforce the maintenance of sinus rhythm after AF ablation [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, the strategy has not been widely recognized and used due to the technical challenges. It was reported that incomplete lesions created anatomical substrates and could bring additional risks of atrial tachyarrhythmias [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Mitral isthmus (MI) ablation is a key component and the most difficult step to achieve bidirectional block in a linear strategy due to its anatomical structure [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The advent of new technologies and tools has increased the possibility of achieving MI bidirectional block, while variable block rates of MI are still reported in different studies [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe ligament of Marshall (LOM), which contains cardiomyocytes, adipose tissue, fibrous tissue, small blood vessels, and nerve tissue, lies on the epicardial surface of the MI area and increases its difficulty of ablation [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. EI-VOM was reported to improve the success rate of MI block and AF ablation [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. We have also reported a novel stepwise catheter ablation method for MI that included EI-VOM, V-shape ablation from the endocardium, and ablation of KATs from the epicardium, obtaining a high bidirectional block rate of 98.3% [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, those methods involved extensive endocardial and epicardial ablation in the procedure [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The imprecise ablation strategy increased the operational difficulty and risk.\u003c/p\u003e\u003cp\u003eHwang et al. reported that the VOM potential could be recorded by an electrophysiological catheter into the VOM [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]; however, the VOM potential was recorded from the epicardium. The QDM catheter is a novel catheter for very high power-short duration (vHPSD) ablation. It contains 3 micro-electrodes (0.086 mm\u0026sup2;) located at the tip of the electrode at an angle of 60\u0026deg;. The clinical feasibility and safety of MI ablations using the QDM catheter have been demonstrated by previous clinical studies [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Dello Russo et al. demonstrated that microelectrode mapping using the QDM catheter revealed higher amplitude, longer duration, and more fractionated electrograms, thereby identifying potential pathology in suspected regions more effectively than standard bipolar electrode mapping [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Therefore, the QDM catheter may be able to record the VOM potential from the endocardium and facilitate precise endocardial ablation.\u003c/p\u003e\u003cp\u003eIn this study, we used the precise mapping capability of the embedded micro-electrodes in the QDM catheter to record the VOM potential from the endocardium, along which the endocardial ablation line was performed precisely. The bipotential recorded by the QDM catheter from the surface of the endocardium includes a higher sharp potential from LA and a lower sharp potential from VOM. We speculate that the sites on the endocardial surface where the VOM potential can be recorded likely correspond to the endocardial terminations of myocardial bundles connecting the endocardium and epicardium in the region surrounding the mitral isthmus. Therefore, the endocardial ablation line guided by the VOM potential recorded via the QDOT catheter is likely to maximize the likelihood of achieving conduction block of MI from the endocardial surface. Our research results thoroughly confirmed the above hypothesis. The results found that the modified stepwise method with the guidance of QDOT MICRO catheter increased the incidence of MI block after a single endocardial ablation line with fewer ablation lesions, thereby avoiding further epicardial ablation.\u003c/p\u003e\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\u003ch2\u003eLimitation\u003c/h2\u003e\u003cp\u003eSeveral important limitations of this trial warrant mention. First, this study is a single-center, randomized, controlled study with a relatively small sample size. Subsequently, the sample size needs to be expanded and a multi-center randomized controlled study should be conducted. Secondly, the present work has not specifically evaluated the long-term outcomes. Our research group followed all patients in our study, and the follow-up results will be published in future studies, providing insights into the short- and long-term prognosis.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eQDOT micro catheter can be used to map the potential of VOM from the endocardium, which facilitates guiding the endocardial MI linear ablation. The technique is able to reduce the endocardial ablation points and the chance of epicardial ablation with comparable complications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eThe study was approved by the ethics committee of Henan provincial people’s Hospital (permission no: 2021092) and was conducted in accordance with the Helsinki Declaration. All patients supplied their signed, informed consent prior to any operations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u0026nbsp;\u003c/strong\u003eNot Applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available request from the corresponding author, Shujuan Dong.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest:\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eProject of Key Science-Technology Foundation of Henan Province (1221023100).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor’s contribution:\u003c/strong\u003e Jingchao Li and Xing Wang wrote the main manuscripts text. Luqian Cui conducted the statistical analysis and prepared table 1-3. Qianqian Feng and Huihui Song performed the operations.Cong Ding,Hailan Wang and Chaoyu Zhao collected the original and conducted radom. Haijia Yu propared the figures in the article. Shujuan Dong and Yingjie Chu designed the research and conducted the quality control of the study. All authors reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Number:\u0026nbsp;\u003c/strong\u003eNCT06145906(ClinicalTrial.gov)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors sincerely thank our clinical specialists, Mr. Liujie Li and Miss Yingrong Xin from Zhengzhou University and Mr. Changyi Yang and Jinlong Li from Biosense Webster, who were very helpful during the ablation procedure and in the collection of CARTO backup data.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eVan Gelder, IC, Rienstra, M, Bunting, KV, et al. 2024 ESC guidelines for the management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS). Eur Heart J. 2024; 45 (36): 3314-3414.\u003c/li\u003e\n \u003cli\u003eJoglar, JA, Chung, MK, Armbruster, AL, et al. 2023 ACC/AHA/ACCP/HRS guideline for the diagnosis and management of atrial fibrillation: a report of the American College of Cardiology/American Heart Association Joint Committee on clinical practice guidelines. Circulation. 2023; 149 (1): e1-e156.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eValderr\u0026aacute;bano, M, Peterson, LE, Swarup, V, et al. Effect of catheter ablation with vein of marshall ethanol infusion vs catheter ablation alone on persistent atrial fibrillation: the VENUS randomized clinical trial. JAMA. 2020; 324 (16): 1620-1628.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eSang, C, Liu, Q, Lai, Y, et al. Pulmonary vein isolation with optimized linear ablation vs pulmonary vein isolation alone for persistent AF: the PROMPT-AF randomized clinical trial. JAMA. 2025; 333 (5): 381-389.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eDerval, N, Tixier, R, Duchateau, J, et al. Marshall-Plan Ablation Strategy Versus Pulmonary Vein Isolation in Persistent AF: A Randomized Controlled Trial. Circ Arrhythm Electrophysiol. 2025; 18 (5): e013427.\u003c/li\u003e\n \u003cli\u003eBecker, AE. Left atrial isthmus: anatomic aspects relevant for linear catheter ablation procedures in humans. J Cardiovasc Electr. 2004; 15 (7): 809-812.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eLi, J, Cui, S, Song, H, et al. A novel stepwise catheter ablation method of the mitral isthmus for persistent atrial fibrillation: efficacy and reproducibility. BMC Cardiovasc Disord. 2023; 23 (1): 466.\u003c/li\u003e\n \u003cli\u003eLi, X, Li, M, Zhang, Y, et al. Simplified stepwise anatomical ablation strategy for mitral isthmus: efficacy, efficiency, safety, and outcome. EUROPACE. 2023; 25 (2): 610-618.\u003c/li\u003e\n \u003cli\u003eHe, B, Yu, W, Li, Y, et al. Acute mitral isthmus block in patients undergoing catheter ablation for atrial fibrillation: efficacy and safety of a systematic stepwise approach. J Interv Card Electrophysiol. 2025; 68 (8): 1647-1659.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eHwang, C, Wu, TJ, Doshi, RN, et al. Vein of marshall cannulation for the analysis of electrical activity in patients with focal atrial fibrillation. Circulation. 2000; 101 (13): 1503-1505.\u003c/li\u003e\n \u003cli\u003eOsorio, J, Hussein, AA, Delaughter, MC, et al. Very high-power short-duration, temperature-controlled radiofrequency ablation in paroxysmal atrial fibrillation: the prospective multicenter Q-FFICIENCY trial. JACC: Clin Electrophysiol. 2023; 9 (4): 468-480.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eSawhney, N, Anand, K, Robertson, CE, et al. Recovery of mitral isthmus conduction leads to the development of macro-reentrant tachycardia after left atrial linear ablation for atrial fibrillation. Circ Arrhythm Electrophysiol. 2011; 4 (6): 832-837.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eVI. On the development of the great anterior veins in man and mammalia; including an account of certain remnants of f\u0026aelig;tal structure found in the adult, a comparative view of these great veins the different mammalia, and an analysis of their occasional peculiarities in the human subject Philos Trans R Soc Lond. 1997; 140 133-170.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eChugh, A, Gurm, HS, Krishnasamy, K, et al. Spectrum of atrial arrhythmias using the ligament of Marshall in patients with atrial fibrillation. Heart Rhythm. 2017; 15 (1): 17-24.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eReddy, VY, Grimaldi, M, De Potter, T, et al. Pulmonary Vein Isolation With Very High Power, Short Duration, Temperature-Controlled Lesions: The QDOT-FAST Trial. JACC Clin Electrophysiol. 2019; 5 (7): 778-786.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003e\u0026nbsp;Osorio, J, Hussein, AA, Delaughter, MC, et al. Very high-power short-duration, temperature-controlled radiofrequency ablation in paroxysmal atrial fibrillation: the prospective multicenter Q-FFICIENCY trial. JACC: Clin Electrophysiol. 2023; 9 (4): 468-480.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eDello Russo, A, Compagnucci, P, Bergonti, M, et al. Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: a dual-center experience. J Cardiovasc Electr. 2023; 34 (5): 1216-1227. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Persistent atrial fibrillation, QDOT MICRO catheter, Mitral isthmus","lastPublishedDoi":"10.21203/rs.3.rs-8308466/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8308466/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground \u003c/strong\u003eEthanol infusion of the vein of Marshall (EI-VOM) has elevated the success rate of mitral isthmus (MI) block in patients with persistent atrial fibrillation (PeAF). However, the procedure involve the extensive endocardial ablation and epicardial ablation, which brought the operational difficulty and risk.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjectives \u003c/strong\u003eThis study aimed to investigate the value of QDOT MICRO (QDM) catheter in mapping the potential of VOM and guiding MI ablation in patients with PeAF.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods \u003c/strong\u003ePatients with PeAF were randomly assigned in a 1:1 ratio to either STSF catheter group using the stepwise method (STSF group) or QDM catheter group using a modified stepwise method (QDM group) for MI ablation. The modified stepwise method was as follows: step 1, The potential of VOM was mapped from endocardium using the QDM catheter. Step 2, EI-VOM. Step 3, precise endocardial ablation guiding by VOM potential. Step 4, QDM catheter was cannulated into the CS for epicardial ablation, especially the ostium of Marshall. The immediate procedural results were compared between the two groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e After excluding 5 patients with unsuccessful EI-VOM, 68 patients were divided into STSF group (36 cases) and QDM group (32 cases). The potential of VOM could be clearly mapped from endocardium using a QDM catheter. Both the accumulated operation time (p=0.032) and ablation time (p\u0026lt;0.001) were significantly shorter in the QDM group compared to the STSF group. QDM group achieved more conduction blocks of MI after a single endocardial line ablation (71.9% vs. 36.1%, p=0.017) with fewer ablation points (p\u0026lt;0.001) compared to the STSF group. The block rate of the MI after endocardial ablation alone was also higher in the QDM group than in the STSF group (90.6% vs. 69.4%; P=0.019), which avoided epicardial ablation. Even if epicardial ablation is necessary, the number of ablation points on the epicardial surface in the QDM group would be fewer than in the STSF group (p\u0026lt;0.001).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e The QDM catheter can be used to map the potential of VOM from endocardium, thereby facilitating precise endocardial mitral isthmus linear ablation. The modified stepwise approach effectively reduces the number of endocardial ablation points and the likelihood of requiring epicardial ablation.\u003c/p\u003e","manuscriptTitle":"Modified stepwise method with the guidance of QDOT MICRO catheter for mitral isthmus ablation in patients with persistent atrial fibrillation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-15 11:02:28","doi":"10.21203/rs.3.rs-8308466/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e6490083-6a2b-4d97-8f01-0d7e7f8e4d9f","owner":[],"postedDate":"December 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-23T17:53:57+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-15 11:02:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8308466","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8308466","identity":"rs-8308466","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}