Left Bundle Branch Pacing Facilitated by Novel Surface Electrocardiography in Comparison with Electrophysiology Recording System

Left Bundle Branch Pacing Facilitated by Novel Surface Electrocardiography in Comparison with Electrophysiology Recording System | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 11 September 2025 V1 Latest version Share on Left Bundle Branch Pacing Facilitated by Novel Surface Electrocardiography in Comparison with Electrophysiology Recording System Authors : Lan Su , Ling Zhu 0009-0000-4339-7544 , Songjie Wang , Shengjie Wu , xiao chen , Zhou-Qing Huang , Liangping Wang , Lei Xu , Xiaohong Zhou , Roy Chung 0000-0001-6415-3880 , and weijian huang 0000-0003-2958-134X [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.175756696.63490025/v1 218 views 134 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Introduction: Left bundle branch pacing (LBBP) had been proven to be feasible and safe in patients with pacing indication. In this study, we assessed the feasibility and safety of LBBP procedure using simplified ECG monitoring and LBBP criteria in comparison with that by using the conventional electrophysiology recording system (EP recording system) and currently adopted LBBP criteria. Methods: The single-center study included 143 consecutive patients from March 2021 to January 2022. The operator was single-blinded to the EP recording system, where they were only avail of a four-lead ECG monitor to observe the morphological changes of pacing QRS and the pacing system analyzer (PSA) to record the intracardiac EGM. Other researchers kept synchronized records of the EP recording system, and analyzed whether the data collected were consistent with LBBP, which was blinded to the implanting operator. Intraoperative data were collected and the safety of follow-up were evaluated. Results: Of 143 patients enrolled, 139 successfully performed LBBP with a success rate of 97.2%, with a perceived clinical judgement consistent with LBBP on the four-lead ECG monitor in concordance with EP recording system at 99.3%. The fluoroscopy time of left bundle branch (LBB) lead deployment had no significant difference with previous studies. Ventricular septal perforation occurred in 2 patients during the procedure. Pacing parameters were stable and heart function improved during follow-up. Conclusion: LBBP implantation approach simply relying on a four-lead ECG system without an EP recording system combined with an analyzer is feasible and safe. Title page Left Bundle Branch Pacing Facilitated by Novel Surface Electrocardiography in Comparison with Electrophysiology Recording System Running title: LBBP Facilitated by Novel Surface Electrocardiography Lan Su, MD, 1,2 Ling Zhu, MD, 3 Songjie Wang, MD, 1,2 Shengjie Wu, MD, 1,2 Xiao Chen, MD, 1,2 Zhouqing Huang, PhD, 1,2 Liangping Wang, PhD, 1,2 Lei Xu, MD, 1,2 Xiaohong Zhou, PhD, 4 Roy Chung, MD, 5 Weijian Huang, MD 1,2 1 Department of Cardiology, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China; 2 The Key Lab of Cardiovascular Disease, Science and Technology of Wenzhou, Wenzhou, China; 3 Department of Cardiology, Yueqing People’s Hospital, Wenzhou, China; 4 Cardiac Rhythm and Heart Failure Division, Medtronic plc, Minneapolis, Minnesota, USA; 5 Section of Cardiac Electrophysiology and Pacing, Heart and Vascular Institute, Cleveland Clinic, Ohio, USA. Co-first author: Lan Su and Ling Zhu Conflict of interest: None declared. Funding: This study was supported by the Science and Technology Project of Wenzhou (Y20210139 to Lan Su). The University-Industry Collaborative Education Program of the Ministry of Education (22097154062650 to Lan Su). Address for correspondence: Weijian Huang, MD; Department of Cardiology, The First Affiliated Hospital of Wenzhou Medical University, Nanbaixiang, Wenzhou 325000, P.R. China. E-mail: [email protected] . OR Dr. Lan Su, Department of Cardiology, The First Affiliated Hospital of Wenzhou Medical University, Nanbaixiang, Wenzhou 325000, P.R. China. E-mail: [email protected] . Word count: 6686 Abstract Introduction: Left bundle branch pacing (LBBP) had been proven to be feasible and safe in patients with pacing indication. In this study, we assessed the feasibility and safety of LBBP procedure using simplified ECG monitoring and LBBP criteria in comparison with that by using the conventional electrophysiology recording system (EP recording system) and currently adopted LBBP criteria. Methods: The single-center study included 143 consecutive patients from March 2021 to January 2022. The operator was single-blinded to the EP recording system, where they were only avail of a four-lead ECG monitor to observe the morphological changes of pacing QRS and the pacing system analyzer (PSA) to record the intracardiac EGM. Other researchers kept synchronized records of the EP recording system, and analyzed whether the data collected were consistent with LBBP, which was blinded to the implanting operator. Intraoperative data were collected and the safety of follow-up were evaluated. Results: Of 143 patients enrolled, 139 successfully performed LBBP with a success rate of 97.2%, with a perceived clinical judgement consistent with LBBP on the four-lead ECG monitor in concordance with EP recording system at 99.3%. The fluoroscopy time of left bundle branch (LBB) lead deployment had no significant difference with previous studies. Ventricular septal perforation occurred in 2 patients during the procedure. Pacing parameters were stable and heart function improved during follow-up. Conclusion: LBBP implantation approach simply relying on a four-lead ECG system without an EP recording system combined with an analyzer is feasible and safe. Key Words: left bundle branch pacing, ECG monitoring, electrophysiology recording system Abbreviations and Acronyms: LBBP= left bundle branch pacing; ECG= electrocardiogram; EP recording system= electrophysiology recording system; PSA= pacing system analyzer; CLBBB= complete left bundle branch block; CRBBB= complete right bundle branch block; NS-LBBP= nonselective left bundle branch pacing; S-LBBP= selective left bundle branch pacing; LVSP= left ventricular septal pacing; Stim-LVAT= time from stimulus to left ventricular activation; PVC= premature ventricular contraction; LBB= left bundle branch; COI= current of injury; LVEF= left ventricular ejection fraction. Introduction His bundle pacing (HBP) and left bundle branch pacing (LBBP) have more recently been accepted as alternative to conventional pacing techniques as it is much more physiologic by utilizing our natural cardiac conduction system 1-3 . Given the limitations of HBP such as high and unstable pacing threshold, and low success rate 4 , Huang et al. introduced the clinical application of LBBP in 2017, which favors a lower and stable pacing threshold with a higher successful implant rate 5-7 . Clinical studies in recent years have verified its procedural feasibility, mid-term safety and favorable clinical benefits 8-10 . Since then, the LBBP has been adopted widely in clinical practice 11 . Currently, most operators who perform LBBP procedure relies on costly and sophisticated electrophysiology recording system (EP recording system) with the ability of capturing 12-lead ECG by observing the transition of ECG QRS morphology transition from LVSP (S-LBBP) to NS-LBBP and injury of current in intracardiac electrogram (EGM) to confirm LBB capture, in addition it also allows caliper measurements of the activation time from pacing stimulation to the peak of R wave along the precordial leads, as a surrogate of left ventricular activation time (LVAT) 12-14 . However, many hospitals do not have the financial resource to acquire such an EP recording system purely for LBBP implantation, therefore limiting the adoption of LBBP in routine clinical practice. Thus, the objective of the present study was to assess the feasibility and safety of LBBP procedure using a simplified 4-lead body surface ECG monitoring and corresponding LBBP criteria in comparison with that by using the conventional EP recording system and currently adopted LBBP criteria. Methods Study patients This single-center prospective study included consecutive patients from March 2021 to January 2022, and the inclusion criteria were: (1) bradycardia with pacing indication such as sick sinus syndrome, atrioventricular block or left bundle branch block requiring cardiac resynchronization therapy; (2) age older than 18 years; Exclusion criteria were: (1) ischemic cardiomyopathy; (2) nonspecific intraventricular conduction delay (IVCD); (3) ventricular septal hypertrophy (end-diastolic thickness over 15 mm); (4) pacing induced cardiomyopathy requiring resynchronization upgrade. The approval of the Ethics Committee of the first affiliated hospital of Wenzhou Medical University was obtained (KY2022-078), and informed consent was obtained from all recruited patients. The trial was conducted in accordance with the principles of the Declaration of Helsinki and was registered in ClinicalTrials.gov (NCT05553431). Implantation process The SelectSecure pacing lead (3830, Medtronic Inc.) and C315His delivery sheath (Medtronic Inc.) were used in all patients. The CPS Direct™ PL Peelable Outer Guide Catheter (Abbott Inc.) will be used when necessary. In this novel simplified body surface ECG approach, we utilized a new modified ECG lead system (Figure 1) that had four-lead body surface ECG monitoring (IntelliVue MP60, Philips Inc) to simulate V5, V1, II and III respectively, The QRS wave displayed on the ECG monitor screen could be amplified according to the operator’s preference, the sweep speed was 50mm/s and the placement of electrodes was shown in Figure 1. The modified V1 lead is as consistent as possible with the standard V1 lead. The pacing system analyzer (PSA, model number: 2290; Medtronic Inc.) could display and record significant LBB potential and injury current through EGM, as well as test pacing parameters. The filter of Electrophysiology recording system (GE CardioLab EP Recording System 2000; GE Healthcare, Milwaukee, WI) was routinely set to 30-500 Hz for collecting high-frequency signals, or 0.5-500Hz when recording ventricular or LBB current of injury (COI). The specific method of LBBP implantation has been well described previously 12, 13 . The procedure for performing LBBP using the 4-lead ECG and PSA is as follows: 1. Pace mapping the His bundle area and locating the initial screw point in the right ventricular septum under fluoroscopic guidance(Figure 2). 2. Observe changes in QRS morphology of the “LBB area fixation beats” and myocardial COI on PSA, monitor unipolar pacing impedance, to determine the depth of pacing lead 15 (Figure 2). 3. When the tip of the lead has reached the left ventricular septum subendocardial, high output pacing was performed to evaluate whether one could shorten the Stim-LVAT and change the QRS morphology, from LVSP to NS-LBBP or from S-LBBP to NS-LBBP (Figure 3). 4. If one achieves “fixation beats”, with acceptable parameters and pacing morphology, no further positioning was done. If the testing parameters are unsatisfactory or the LBB capture is defined as unsuccessful, the lead depth is adjusted or repositioned until the LBB capture threshold is below 1.5 V/0.5ms. Confirmation of LBB capture was conducted by the operator’s visual assessment with the guidance of a simplified 4-lead ECG and PSA while simultaneously blinded to an EP recording system, managed by an experienced EP laboratory staff. The operator’s visual observation of the electrophysiological characters included the RBBB pattern of the paced QRS in modified V1, the change of paced QRS with high and low output pacing, the abrupt change of Stim-LVAT in V5’ lead, RBBB pattern fixation beats and LBB potential of intracardiac EGM on the PSA. Simultaneously, the experienced EP laboratory staff independently recorded pacing ECG morphology, intracardiac EGM of the EP recording system and measured all LBBP-related variables and confirmed LBB capture based on the current LBBP criteria 14 . Intraoperative data were collected, including implant time, fluoroscopy time, fluoroscopy time of His lead placement, fluoroscopy time of LBBP lead placement, pacing parameters, intraoperative complications, and success rate. Definition of successful left bundle branch pacing implantation LBB capture using this novel simplified technique can be summarized by 1) Paced RBBB pattern in V1; 2) the new R’ wave or widening R’ wave in V1 with high output pacing; 3) Visible abrupt change of Stim-LVAT in lead V5; 4) fixation beats; 5) LB potential and LB COI noted on PSA. If operator’s LBBP judgement was consistent with LBBP confirmed by the EP recording system, the LBBP implantation was deemed as success; if the operator’s LBBP confirmation was confirmed as non-LBBP by the EP recording system, the LBBP implantation was assigned as failure and the reasons of failure were truthfully documented and intraoperative information was recorded, then the operator re-performed LBBP with the assistance of the EP recording system (Figure 3). Definition of selective LBBP(S-LBBP) and non-selective LBBP(NS-LBBP) LBBP criteria have been well described in previous studies 14, 16-18 , based on which we further clarify the LBBP criteria for the simplified ECG-guided LBBP implantation as below: S-LBBP is defined as capturing only the LBB： 1. When the output is reduced, the R wave in lead V1’ widens while the S wave in lead V5’ deepens; the paced QRS in lead V1’ is M or rsR’ pattern and the QRS complex duration is wide with a notch (Figure 4A). 2. There is no obvious change in Stim-LVAT visually on V5. 3. Discrete component is visible between the pacing stimulus and the onset of ventricular potential on the EGMs of PSA (Figure 5D). NS-LBBP simultaneously captures both the LBB and the local myocardium during pacing. As a result, the shift in the QRS morphology could be observed when varying the output voltage. A. When the output is increased, the QRS in lead V1’ becomes a QR mode or a smaller R wave, and the S wave in V5’ becomes smaller; there is no obvious change in Stim-LVAT, indicating S-LBBP to NS-LBBP (Figure 4A). B. When the output is increased from a capture threshold, a progressive R wave in lead V1’, associated with shortening of the Stim-LVAT, suggests a transition from LVSP to NS-LBBP 19 (Figure 4A). C. Simultaneous capture of the conduction bundle and local myocardium has no discrete component on the EGMs of PSA (Figure 5D). Follow-up Patients were followed for at least three months after with their pacing parameters, 12-lead electrocardiograms, echocardiograms, and post-operative complications documented during follow-up. Statistical analysis Continuous variables are expressed as mean ± SD, enumeration data are expressed as the number of cases (%) and using χ 2 test, measurement data using Student‘s t test, paired t test to analyze the difference between baseline and follow-up, P ≤ 0.05 is considered statistically significant difference. Statistical analysis was performed using statistical software packages such as SPSS Version 23 or R Software Version 4.1. Results Baseline characteristics Patients’ baseline characteristics are summarized in Table 1. Among all enrolled patients, atrioventricular block was presented in 64 patients, sick sinus syndrome was noted in 54 patients. According to the QRS duration of baseline ECG, the patients were divided into CLBBB group (n=37) and non-CLBBB group (n= 106). The non-CLBBB group included CRBBB group (n= 15) and narrow QRS group (n= 91). The mean New York heart function class was 1.1 ± 1.2, and the mean New York heart function class of patients in the CLBBB subgroup was 2.3 ± 0.9, and the proportion of patients with cardiomyopathy heart failure in the CLBBB subgroup was 67.6% (25/37). Intraoperative characteristics LBBP was successfully performed in 139 patients with a success rate of 97.2%, and left ventricular septal pacing in the remaining 4 patients. Among the 4 patients, the pacing lead tip could not be screwed deeply, possible reason of septal fibrosis in 2 patients, high LBB capture threshold (>1.5V/0.5ms) in 2 patients. One patient was re-performed LBBP under the EP recording system due to inconsistent judgment, which was not included in the postoperative analysis. Total implantation time (from skin cut to suture) was 78.9±26.5min, total fluoroscopy time 9.5±6.1min and fluoroscopy time of LBB lead deployment 3.0±2.6min. (Table 2). Changes of surface electrocardiogram Paced RBBB pattern in lead V1’ The operator’s ECG monitoring with simplified 4-lead ECG showed clear rSR’ or QR in RBBB pattern in lead V1’ in all 143 patients, which was consistent with those observed in the EP recording system (Figure 4A), yielding100% accuracy. Since RBBB QRS pattern can be observed during left ventricular septal capture, this may not be used as an only criterion to confirm LBB capture. (2) QRS morphological changes Unipolar pacing output was increased from low to high during testing with attention paid to V1 pacing morphology changes. Based on ECG monitoring, the operator monitored the morphological changes of R’ wave on lead V1’ of the simplified 4-lead ECG. We considered LBB capture was noted when the change of R’ wave in lead V1’ was observed during pacing output change. With the ECG monitor, the operator could observe two types of LBB capture transitions: NS-LBBP to S-LBBP or LVSP to NS-LBBP (Figure 4). NS-LBBP to S-LBBP NS-LBBP to S-LBBP transition during decremental of pacing outputs were noted in 126 patients, which was 100% consistent with observation by the EP recording system. Among 126 patients, 114 patients showed widening of the R’ wave in lead V1’, while all 126 patients showed deepening of the S wave in lead V5’ during S-LBBP (Table 3). LVSP to NS-LBBP Changes in LVSP to NS-LBBP were observed in 121 patients on the EP recording system. AS mentioned previously, RBBB pacing pattern alone does not guarantee LBB capture. The 121 patients that demonstrated changes of pacing QRS pattern on the V1’ lead (14 cases of emerging R wave, 90 cases of widening R’ wave and 17 cases of narrowed R’ wave) were associated with abrupt shortening of Stim-LVAT on V5 lead. The emerging R wave was defined as a QRS change from QS type to QR/rSR’. Notably, the phenomenon of the emerging R wave mainly occurred in the CLBBB group. And there were 17 patients with reduced R waves when transitioned from LVSP to NS-LBBP. We considered it to be caused by retrograde activation of the right bundle branch during non-selective capture of LBB 20 . Visible abrupt change of Stim-LVAT in V5’ lead The operator could clearly observe the visual changes of Stim-LVAT(19.4±8.4ms) in 110 patients on ECG monitoring while the EP recording system detected changes of Stim-LVAT in 120 patients (18.7±8.4ms), yielding a 91.7% concordance. In patients whose Stim-LVAT was not clearly judged to be shortened, the operator judged the LBB capture by the change in the QRS morphology. There was no statistical difference between CLBBB group (87.5%, N=28/32), CRBBB group (69.2%, N=10/12) and narrow QRS group (92.1%, N=72/76). Notably, in patients (93/120) with a ΔStim-LVAT≥12ms, the change could be recognized visually with a specificity of 100%. The operator made a successful judgment of 120 patients through the four-lead ECG monitoring, and only one patient was adjudicated inconsistently with the EP recording system. This case had second-degree type II atrioventricular block with a QRS duration of 100ms. When the output was increased, the QRS pattern changed from LVSP (Stim-LVAT=78ms) to NS-LBBP (67ms), and LVSP was misjudged as S-LBBP. PVC with RBBB morphology during fixation When the tip of the lead is close to the LBB area, mechanical stimulation of the LBB or the adjacent septal myocardium during screwing-in can lead to PVC with RBBB pattern in ECG lead V1’ (Figure 4B). These fixation beats during lead screw-in attempt was observed in 122 of 143 patients (85.3%) with 100% consistency between the operator’s observation and the EP recording system. (Table 3). Phenomena of intracardiac electrocardiogram LBB potentials were recorded using the EP recording system in 86.8% of patients (125/143). In the narrow QRS group, the operator observed LBB potential in only 73.3% of patients (66/90) through EGM analysis on PSA, which was significantly lower than the recording rate achieved by the EP recording system. This discrepancy may be attributed to PSA’s inability to adjust filtering during recording, resulting in some Purkinje potentials with smaller amplitudes being disregarded (Figure 5), when the amplitude of LBB potential on intracardiac EGM from non-CLBBB group≥0.16mV (N=41), PSA demonstrated a sensitivity of 100% for detecting LBB potential. The average amplitude of LBB potential recorded by PSA was measured as 0.28±0.26mV, while those that could be captured by the EP recording system but not by PSA had an average amplitude of 0.08±0.04mV. Additionally, potential-related COI was observed in the EGM recordings from PSA in 22.4% (32/143; or equivalently, among 34% of patients with LBB potential) cases examined. The ventricular COI recording rate reached a consistent value of 100% both for PSA and EP recording systems (Table3). Pacing parameters Of the total 139 successful LBBP implant patients 135 patients were included in the statistical analysis, one patient did not complete the follow-up, the follow-up completion rate was 99.3%. One patient was re-performed LBBP using EP recording system and 2 patients had the pacing capture threshold of the LBB increased to more than 3V/0.5ms during follow-up, were not included in the statistical analysis. The LBB capture threshold was slightly increased at 3-month follow-up (0.60±0.25V/0.5ms) compared with the immediately postoperative period (0.53±0.23V/0.5ms, P=0.008). There was no statistically significant change in LV septal myocardium capture threshold between 3-month follow-up (0.63±0.25V/0.5ms) and the immediately postoperative period (0.60±0.26V/0.5ms, P=0.170), the unipolar impedance was significantly lower at 3-month follow-up (498.9±108.5Ω) than the immediate postoperative period (377.2±47.4Ω, P<0.001). Intraoperative and postoperative complications During the operation, ventricular septal perforation was suspected in 2 patients, which indicated that the EGM amplitude on the PSA decreased, the impedance dropped below 450Ω from 600Ω, and the capture threshold increased from less than 1.5V/0.5ms to more than 5V/0.5ms. The pacing leads were repositioned. In 2 patients, the LBB capture threshold increased due to withdrawal of the sheath caused by micro-displacement of the lead tip; this issue was resolved by changing its position and re-fixing it. In one patient, there was a puncture in the thoracoacromial artery while attempting axillary vein puncture; however, it recovered without intervention. No serious complications occurred during follow-up. Cardiac function and LVEF improvement Three groups of NYHA functional class showed improvement compared to the baseline, with the CLBBB group demonstrating the most significant improvement (1.6±0.7 from baseline 2.3±0.9, P<0.001). The three-month follow-up in the CLBBB group revealed a significant increase in LVEF compared to baseline (53.7±11.9% vs. baseline 41.3±14.7%, P<0.001), and there was no statistical difference between the CRBBB group (66.7±5.1% vs. 68.0±6.3%, P=0.548) and the narrow QRS group (66. 7±9.1% vs. 65.9±8.6%, P=0.396). Discussion Feasibility and safety In this study, in the absence of guidance from an EP recording system, the operator could rely on the simplified 4-lead body surface ECG and the PSA to accurately determine whether LBB was captured at low output（<1.5V/0.5ms） and achieve a high implantation success rate (97.2%). LBB capture with this simplified ECG approach showed a remarkable concordance rate of 99.3% with its confirmation by the EP recording system. Compared with our previous studies, the intraoperative operation time and the fluoroscopy time was similar (78.8±26.4 versus 86.4±43.5min in the previous report 9 , 9.5±6.1min versus 9.7±7.3min reported in the previous studies 21 ). Our findings confirm the feasibility of LBBP operation without the need for an EP recording system. Myocardial COI on PSA and impedance testing could help avoid septum perforation and enhance the safety of lead implant. The LBB capture threshold remained low and stabilized at the 3-month follow-up, demonstrating safe short-term outcomes consistent with previous studies of LBBP under standard practice. We had two cases with suspected intraoperative septal perforation, notably. In the acute phase, if the EP recording system records LBB potential and COI, we would typically wait for a lower threshold. PSA may not exhibit the same degree of small potential and COI as the EP recording system does, making it more likely to be over-screwed during the acute phase and leading to perforation. The primary focus of the simplified method The main purpose of utilizing the simplified method under a 4-lead ECG monitoring for LBBP confirmation is to observe changes in the body surface’s 4-lead ECG, including: ① the QRS morphological changes of LVSP, NS-LBBP, and S-LBBP could be evaluated by altering the pacing voltage outputs; ② the presence of LBB capture can be confirmed by observing the visible shortening of Stim-LVAT in lead V5; ③ observe the intracardiac electrocardiogram of PSA to determine the depth and accuracy of the electrode by LBB potential and the COI of V wave. The accuracy of diagnosing LBB capture can be significantly improved by considering both indicators mentioned above, rather than relying solely on one indicator. All patients in the study exhibited an RBBB pacing pattern. If the pacing ECG displays changes in one of the above factors, it can accurately confirm the presence of LBBP. The change in QRS morphology confirms the capture of left bundle branch When there is no EGM guidance, the operator mainly focuses on the QRS changes of captured conduction system. With HBP, due to the long HV interval, noticeable QRS changes occur from ventricular septum capture to His bundle capture, which is easily observable. Conversely with LBBP, both LBBP and LVSP can exhibit a RBBB pacing pattern. Careful observation of the subtle differences between the two paced ECG morphologies is necessary for differentiation. The essence of these QRS changes lies in: (1) while capturing LBB, there are two paced patterns: S-LBBP and NS-LBBP. The right bundle branch delay is more pronounced in S-LBBP due to the lack of capture by surrounding myocardium, resulting in a wider QRS complex and a deep S wave in lead V5’. (2) during the transition from LVSP to NS-LBBP, the Stim-LVAT in lead V5’ may exhibit abrupt shortened in duration exceeding 12ms, which can be visually discerned. Though the ECG monitoring cannot be measured, but it can be repeatedly verified by adjusting the output voltage and observing the synchronous changes in the shape and width of the QRS complex. The key point is to identify differences in QRS changes, with the S-LBBP pattern being the most sensitive and specific feature. The techniques for repeated verification are recommended as follows: (1) pacing with lower output (1V/0.5ms) first, followed with a higher output (10V/0.5ms), paying attention to changes in paced ECG morphology and Stim-LVAT in V5 lead. (2) the pacing test method involves repeatedly changing the voltage near the LBB capture threshold for identification. This helps distinguish the capture threshold of LV septal and LBB. Alternatively, increasing the pacing frequency to over 130 bpm can also aid differentiation due to differences in refractory period between the myocardium and conduction bundle. 13 Abrupt shortening of Stim-LVAT is important In previous studies, the abrupt shortening of Stim-LVAT during increasing output was considered significant evidence for capturing LBB. In our study, while the abrupt shortening of Stim-LVAT remains equally important, only visually noticeable changes in Stim-LVAT (ΔStim-LVAT≥12ms) can be observed due to the absence of a measurement function in the four-lead ECG monitor. Therefore, using the V6-V1 interpeak interval as a criterion for determining the capture of the LBB is not feasible 17, 22 . Recently, simple EP recording systems and ECG tracer systems have been proposed. These systems with freezing function and calipers are very helpful for in determining LBB capture. Patients in the CLBBB group are more probable to be identified and assessed. In this study cohort, LBBP could be accurately judged intraoperatively in 100% of patients with CLBBB. From the intrinsic morphology of LBBB to the narrow QRS of septal-derived PVC and then to the typical RBBB morphology after LBB capture, sufficient and obvious changes can be easily identified and assessed. Retrograde atrial activation from ventricle due to proximal left bundle or distal His block is rare in patients with LBB block, therefore S-LBBP patterns are more likely to be observed across the distal end of the block site at low output, accounting for 94.7% (N=36/38) in this study. The role of PSA In addition to routine pacing analysis, PSA can also record EGMs. It can help record conduction potential with an amplitude greater than 0.1mv ahead of the V wave, and in some cases, record the potential COI (Figure 5). The left bundle potential associated with COI can serve as a confirmation of LBB capture and lead positioning. Moreover, this observation has also been noted to be correlated to lower and stable capture threshold at follow up 23, 24 . If the immediate threshold is too > 1.5V @0.5msec in the presence of large COI, there is no need to advance the lead deeper or changing positions as we would recommend waiting for a few minutes to allow improvement in the capture threshold. Observation of an acute amplitude change in the V wave COI in PSA can determine whether the lead has perforated the ventricular septum perforated and avoid further deployment of the lead 25 . Study limitations This study is a single-center study with a sample size of 143 cases. Patients with acute anterior myocardial infarction, hypertrophic cardiomyopathy and nonspecific IVCD were not included in the group. Considering the potential complexities in assessing LBB capture among patients with the aforementioned conditions, only two experienced operators with extensive experience in assessing LBB capture were included in the study. Therefore, it is recommended that operators who are still in the learning curve familiarize themselves with the electrophysiological and operating procedures of LBBP before transitioning to the simplified method. We also did not involve other stylet-driven pacing leads which may result in different implantation outcomes. And only one type of PSA was used, which might affect the observation of potential and COI. Conclusion The simplified LBBP implantation method without an EP recording system and relying only on a simplified body surface ECG combined with PSA is clinically feasible and safe. It is recommended that the operator pays close attention to pacing QRS changes during the LBBP procedure, including the S-LBBP/NS-LBBP/LVSP morphology transformation which accompanies an obvious shortening of Stim-LVAT. These are key nuances that can be observed to determine LBB capture. In addition, presence of left bundle COI on PSA can also be a strong predictor of low stable capture threshold at follow up. LBBP has gained significant clinical adoption in China. This technique enables primary hospitals, even without EP recording system, to achieve comparable left bundle branch capture pacing. Reference 1.Huang, W., S. Wang, L. Su, G. Fu, Y. Su, K. Chen, et al., His-bundle pacing vs biventricular pacing following atrioventricular nodal ablation in patients with atrial fibrillation and reduced ejection fraction: A multicenter, randomized, crossover study-The ALTERNATIVE-AF trial. Heart Rhythm 2022 19(12):1948-1955.2.Curila, K., R. Prochazkova, P. Jurak, M. Jastrzebski, J. Halamek, P. Moskal, et al., Both selective and nonselective His bundle, but not myocardial, pacing preserve ventricular electrical synchrony assessed by ultra-high-frequency ECG. Heart Rhythm 2020 17(4):607-614.3.Vijayaraman, P., N. Patel, S. Colburn, D. Beer, A. Naperkowski, and F. A. Subzposh, His-Purkinje Conduction System Pacing in Atrioventricular Block: New Insights Into Site of Conduction Block. JACC Clin Electrophysiol 2022 8(1):73-85.4.Hua, W., X. Fan, X. Li, H. Niu, M. Gu, X. Ning, et al., Comparison of Left Bundle Branch and His Bundle Pacing in Bradycardia Patients. JACC Clin Electrophysiol 2020 6(10):1291-1299.5.Huang, W., L. Su, S. Wu, L. Xu, F. Xiao, X. Zhou, et al., A Novel Pacing Strategy With Low and Stable Output: Pacing the Left Bundle Branch Immediately Beyond the Conduction Block. Can J Cardiol 2017 33(12):1736 e1731-1736 e1733.6.Huang, W., L. Su, S. Wu, L. Xu, F. Xiao, X. Zhou, et al., Long-term outcomes of His bundle pacing in patients with heart failure with left bundle branch block. Heart 2019 105(2):137-143.7.Cai, M., S. Wu, S. Wang, R. Zheng, L. Jiang, L. Lian, et al., Left Bundle Branch Pacing Postatrioventricular Junction Ablation for Atrial Fibrillation: Propensity Score Matching With His Bundle Pacing. Circ Arrhythm Electrophysiol 2022 15(10):e010926.8.Huang, W., S. Wu, P. Vijayaraman, L. Su, X. Chen, B. Cai, et al., Cardiac Resynchronization Therapy in Patients With Nonischemic Cardiomyopathy Using Left Bundle Branch Pacing. JACC Clin Electrophysiol 2020 6(7):849-858.9.Su, L., S. Wang, S. Wu, L. Xu, Z. Huang, X. Chen, et al., Long-Term Safety and Feasibility of Left Bundle Branch Pacing in a Large Single-Center Study. Circ Arrhythm Electrophysiol 2021 14(2):e009261.10.Wu, S., L. Su, P. Vijayaraman, R. Zheng, M. Cai, L. Xu, et al., Left Bundle Branch Pacing for Cardiac Resynchronization Therapy: Nonrandomized On-Treatment Comparison With His Bundle Pacing and Biventricular Pacing. Can J Cardiol 2021 37(2):319-328.11.Chen, X., Y. Ye, Z. Wang, Q. Jin, Z. Qiu, J. Wang, et al., Cardiac resynchronization therapy via left bundle branch pacing vs. optimized biventricular pacing with adaptive algorithm in heart failure with left bundle branch block: a prospective, multi-centre, observational study. Europace 2022 24(5):807-816.12.Huang, W., X. Chen, L. Su, S. Wu, X. Xia, and P. Vijayaraman, A beginner’s guide to permanent left bundle branch pacing. Heart Rhythm 2019 16(12):1791-1796.13.Su, L., K. A. Ellenbogen, and W. Huang, Left Bundle Branch Pacing: How I Do It? Card Electrophysiol Clin 2022 14(2):165-179.14.Wu, S., X. Chen, S. Wang, L. Xu, F. Xiao, Z. Huang, et al., Evaluation of the Criteria to Distinguish Left Bundle Branch Pacing From Left Ventricular Septal Pacing. JACC Clin Electrophysiol 2021.15.Jastrzębski, M., G. Kiełbasa, P. Moskal, A. Bednarek, A. Kusiak, T. Sondej, et al., Fixation beats: A novel marker for reaching the left bundle branch area during deep septal lead implantation. Heart Rhythm 2021 18(4):562-569.16.Chen, X., S. Wu, L. Su, Y. Su, and W. Huang, The characteristics of the electrocardiogram and the intracardiac electrogram in left bundle branch pacing. J Cardiovasc Electrophysiol 2019 30(7):1096-1101.17.Jastrzebski, M., G. Kielbasa, K. Curila, P. Moskal, A. Bednarek, M. Rajzer, et al., Physiology-based electrocardiographic criteria for left bundle branch capture. Heart Rhythm 2021 18(6):935-943.18.Burri, H., M. Jastrzebski, Ó Cano, K. Čurila, J. de Pooter, W. Huang, et al., EHRA clinical consensus statement on conduction system pacing implantation: endorsed by the Asia Pacific Heart Rhythm Society (APHRS), Canadian Heart Rhythm Society (CHRS), and Latin American Heart Rhythm Society (LAHRS). Europace 2023 25(4):1208-1236.19.Wu, S., P. S. Sharma, and W. Huang, Novel left ventricular cardiac synchronization: left ventricular septal pacing or left bundle branch pacing? Europace 2020 22(Suppl_2):ii10-ii18.20.Sun, W., G. A. Upadhyay, and R. Tung, Influence of Capture Selectivity and Left Intrahisian Block on QRS Characteristics During Left Bundle Branch Pacing. JACC Clin Electrophysiol 2022 8(5):635-647.21.Sharma, P. S., N. R. Patel, V. Ravi, D. V. Zalavadia, S. Dommaraju, V. Garg, et al., Clinical outcomes of left bundle branch area pacing compared to right ventricular pacing: Results from the Geisinger-Rush Conduction System Pacing Registry. Heart Rhythm 2022 19(1):3-11.22.Jastrzębski, M., H. Burri, G. Kiełbasa, K. Curila, P. Moskal, A. Bednarek, et al., The V6-V1 interpeak interval: a novel criterion for the diagnosis of left bundle branch capture. Europace 2022 24(1):40-47.23.Su, L., T. Xu, M. Cai, L. Xu, P. Vijayaraman, P. S. Sharma, et al., Electrophysiological characteristics and clinical values of left bundle branch current of injury in left bundle branch pacing. J Cardiovasc Electrophysiol 2020 31(4):834-842.24.Shali, S., W. Wu, J. Bai, W. Wang, S. Qin, J. Wang, et al., Current of injury is an indicator of lead depth and performance during left bundle branch pacing lead implantation. Heart Rhythm 2022.25.Ponnusamy, S. S., W. Basil, and P. Vijayaraman, Electrophysiological characteristics of septal perforation during left bundle branch pacing. Heart Rhythm 2022 19(5):728-734. Figure legends Central Illustration Figure 1. New Modified ECG Lead System. The new modified ECG lead system used a five-electrode monitoring cable with four leads. The right arm (RA) electrode was placed in left shoulder and the left arm (LA) electrode was placed in the right fourth intercostal space to obtain a modified V1’ lead configuration. The left leg (LL) electrode and the right leg (RL) electrode were placed in left and right lower limbs respectively. Modified lead II was obtained by LA and LL electrodes, while modified lead III was obtained by RA and RL electrode. The fifth(V) electrode was placed in the stand V5 lead position. Figure 2. The Routine of Left Bundle Branch Pacing. The operation of LBBP had been described in detail in previous studies, and several unconventional methods of His bundle location had emerged. A simplified method using ECG monitor and PSA was proposed for pacing mapping in the LBB area. HB= his bundle; ICE= intracardiac echocardiogram; PSA= pacing system analyzer. Figure 3. Flowchart for the Simplified Left Bundle Branch Pacing. The operator was single-blind to the EP recording system and determined the LBB capture by signs of ECG monitoring and PSA. Other researchers synchronously observed the EP recording system, evaluated the operator’s judgments, and recorded relevant information. PSA= pacing system analyzer; COI= current of injury; EGM = electrogram. Figure 4. Electrophysiological Characteristics on ECG Monitoring and EP recording system. (A) At the initial depth, a transition from LVSP to NS-LBBP was noted as output increased, and paced RBBB pattern was observed (yellow asterisk). Stim-LVAT could be measured on the EP recording system and reduced from 101ms to 71ms. At the same time, it was also observed that Stim-LVAT was abruptly shortened in lead V5 on ECG monitoring (red arrow), although it was not as intuitive as EP recording system. At the final depth, QRS morphology shifted from S-LBBP to NS-LBBP as output increased. On ECG monitoring, it could be observed that the R wave in lead V1 of S-LBBP was wider, and the S wave in lead V5 was deeper. Stim-LVAT in lead V5 of S-LBBP and NS-LBBP were similar. (B) The PVCs with RBBB morphology were obviously different from the beat of intrinsic rhythm (the first beat), and it can be easily distinguished in ECG monitoring and EP recording system. LVSP= left ventricular septal pacing; NS-LBBP= nonselective left bundle branch pacing; S-LBBP= selective left bundle branch pacing; Stim-LVAT= time from stimulus to left ventricular activation; PVC= premature ventricular contraction. Figure 5. Electrophysiological Characteristics on PSA. (A, B, C) The LBB potential and COI (red circle) of three cases on PSA. One patient could be noted to have obvious LBB potential on PSA, and the amplitude of LBB potential measured on EP recording system was 0.2mv. And COI of ventricular and LBB potential could also be identified. (D) Obvious discrete component (red arrow) between the pacing stimulus and the onset of ventricular potential could be observed on the EGMs of PSA while S-LBBP. LBB= left bundle branch; COI= current of injury; NS-LBBP= nonselective left bundle branch pacing; S-LBBP= selective left bundle branch pacing; EGM = electrogram. Table 1 Baseline characteristics Baseline characteristics All, N=143 CLBBB, N=37 Non-CLBBB, N=106 CRBBB, N=15 Narrow QRS(≤120ms), N=91 Age (y) 72.2±10.3 73.2±8.0 74.9±7.0 71.4±11.5 BMI (kg/m²) 24.0±3.6 24.1±3.5 25.3±2.9 23.7±3.8 Male 75(52.4) 19(51.4) 11(73.3) 45(49.5) Medical history CAD 38(26.6) 12(32.4) 4(26.7) 22(24.2) NICM 34(23.8) 25(67.6) 0(0) 9(9.9) Kidney dysfunction 29(20.3) 12(32.4) 3(20.0) 14(15.4) AF 51(35.7) 11(29.7) 3(20.0) 37(40.7) SSS 54(37.8) 2(5.4) 6(40.0) 46(50.5) AVB 64(44.8) 9(24.3) 12(80.0) 43(47.3) NYHA 1.1±1.2 2.3±0.9 1.3±1.0 0.6±1.0 Echocardiographic parameters LVEF (%) 60.1±15.4 42.1±15.4 67.7±5.7 66.2±9.6 LVEDd (mm) 51.4±6.9 56.6±8.1 51.1±4.9 49.4±5.4 LAD (mm) 45.0±6.0 45.9±4.9 45.6±5.5 44.5±6.5 IVS (mm) 10.4±1.4 10.4±1.4 10.5±1.6 10.4±1.3 QRS duration (ms) 117.3±33.8 164.9±16.9 142.4±13.7 93.8±7.6 CLBBB= complete left bundle branch block; CRBBB= complete right bundle branch block; BMI= body-mass index; CAD= coronary artery disease; NICM= nonischemic cardiomyopathy; AF= atrial fibrillation; SSS= sick sinus syndrome; AVB= atrioventricular block; NYHA= New York Heart Association; LVEF= left ventricular ejection fraction; LVEDd= left ventricular end-diastolic dimension; LAD= left atrial diameter; and IVS= interventricular septal. Table 2 Intraoperative Information All, N=143 CLBBB, N=37 Non-CLBBB, N=106 CRBBB, N=15 Narrow QRS(≤120ms), N=91 Procedure duration, min 78.9±26.5 91.7±22.2 85.9±36.3 72.5±24.2 Total fluoroscopy time, min 9.5±6.1 11.2±7.3 12.1±5.0 8.3±5.4 Total fluoroscopy dose, mGy 44.9±31.7 54.2±36.5 56.7±17.0 39.2±30.2 Fluoroscopy time of His lead deployment, min 0.6±0.7 0.7±0.7 0.7±0.6 0.6±0.7 Fluoroscopy dose of His lead deployment, mGy 3.9±3.6 3.7±3.4 3.9±2.9 3.9±3.8 Fluoroscopy time of LBB lead deployment, min 3.0±2.6 3.2±2.7 3.5±2.9 2.8±2.6 Fluoroscopy dose of LBB lead deployment, mGy 19.3±16.6 20.6±15.1 24.8±13.6 17.8±17.6 Judgement consistent with EP recording system, N(%) 142(99.3) 37(100) 15(15) 90(98.9) Left bundle branch pacing in final, N(%) 139(97.2) 37(100) 13(86.7) 89(97.8) CLBBB= complete left bundle branch block; CRBBB= complete right bundle branch block; LBB= left bundle branch; EP recording system= electrophysiology recording system. Table 3 Comparison of Electrophysiological Characteristics between ECG monitoring, PSA, and EP recording System Total, N=143 CLBBB group, N=37 CRBBB group, N=15 Narrow QRS group, N=91 ECG or PSA EP recording system Coincidence rate (%) ECG or PSA EP recording system Coincidence rate (%) ECG or PSA EP recording system Coincidence rate (%) ECG or PSA EP recording system Coincidence rate (%) Changes of surface electrocardiogram Paced RBBB pattern in lead V1, N 143 143 100 37 37 100 15 15 100 91 91 100 NS-LBBP to S-LBBP*, N 126 126 100 36 36 100 11 11 100 79 79 100 Widening R’ wave in lead V1, N 7 7 100 0 0 / 0 0 / 7 7 100 Narrowed R’ wave in lead V1, N 119 119 100 36 36 100 11 11 100 72 72 100 Deepening S wave in lead V5, N 126 126 100 36 36 100 11 11 100 79 79 100 LVSP to NS-LBBP*, N 119 120 99.2 32 32 100 12 12 100 75 76 98.7 Emerging R’ wave in lead V1, N 14 14 100 11 11 100 0 0 / 3 3 100 Widening R’ wave in lead V1, N 86 90 95.6 19 20 95.0 9 11 81.8 58 59 98.3 Narrowed R’ wave in lead V1, N 15 16 93.8 2 2 100 1 1 100 12 13 92.3 Visible abrupt change of Stim-LVAT in lead V5, N 110 120 91.7 28 32 87.5 10 12 69.2 72 76 92.1 PVCs with RBBB morphology during fixation, N 122 122 100 28 28 100 11 12 100 83 83 100 PSA LBB potential † , N 83 125 66.4 9 22 40.9 8 13 61.5 66 90 73.3 COI of LBB potential, N 32 94 34.0 2 13 15.4 2 11 18.2 28 70 40.0 Ventricular COI, N 143 143 100 37 37 100 15 15 100 91 91 100 PSA= pacing system analyzer; EP recording system, electrophysiology recording system; NS-LBBP, nonselective left bundle branch pacing; S-LBBP, selective left bundle branch pacing; LVSP, left ventricular septal pacing; Stim-LVAT, time from stimulus to left ventricular activation; PVC, premature ventricular contraction; LBB, left bundle branch; COI, current of injury, other abbreviations as in Table 1.* The transition from NS-LBBP to S-LBBP or LVSP to NS-LBBP was caused by changing output at the same pacing site. † LBB potentials of CLBBB group were recorded on the PSA during corrective HBP and during RBBB morphology escape rhythm from the LBB fascicles. Information & Authors Information Version history V1 Version 1 11 September 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords clinical: electrophysiology – conduction disturbances clinical: implantable devices – biventricular pacing/defibrillation clinical: implantable devices – lead implantation/extraction clinical: implantable devices – pacemaker-bradyarrhythmias clinical: implantable devices – physiologic pacing Authors Affiliations Lan Su The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Ling Zhu 0009-0000-4339-7544 Yueqing People's Hospital View all articles by this author Songjie Wang The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Shengjie Wu The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author xiao chen The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Zhou-Qing Huang The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Liangping Wang The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Lei Xu The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Xiaohong Zhou Medtronic Cardiac Rhythm and Heart Failure Management View all articles by this author Roy Chung 0000-0001-6415-3880 Cleveland Clinic Cardiac Electrophysiology and Pacing Section View all articles by this author weijian huang 0000-0003-2958-134X [email protected] The First Affiliated Hospital of Wenzhou Medical University Department of Cardiology View all articles by this author Metrics & Citations Metrics Article Usage 218 views 134 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Lan Su, Ling Zhu, Songjie Wang, et al. Left Bundle Branch Pacing Facilitated by Novel Surface Electrocardiography in Comparison with Electrophysiology Recording System. Authorea . 11 September 2025. DOI: https://doi.org/10.22541/au.175756696.63490025/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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