Importance Left bundle-branch pacing (LBBP) has been proposed as an alternative to biventricular pacing (BiVP) for patients with heart failure with left bundle-branch block (LBBB). However, robust clinical evidence from randomized clinical trials is lacking. Objective To evaluate the long-term clinical outcomes of LBBP and BiVP. Design, Setting, and Participants This multicenter, prospective, randomized clinical trial enrolled 200 patients at 6 centers in China with a left ventricular ejection fraction (LVEF) of 35% or less and LBBB from October 2020 to March 2022. This study was took place from October 2020 to September 2024. These data were analyzed September 2024 to December 2024. Interventions Patients were randomly assigned in a 1:1 ratio to receive either LBBP or BiVP. Main Outcomes and Measures The primary end point was the time to death from any cause or heart failure hospitalization (HFH). The secondary end points included all-cause death, HFH, echocardiographic response (absolute increase in LVEF ≥5%), and super response (absolute increase in LVEF ≥15% or improvement of LVEF to ≥50%) rates. Results Of the 200 included patients, 136 were male and 64 were female. The success rate was 98% in the LBBP group and 94% in the BiVP group ( P = .28). The median follow-up duration was 36 (range, 33-39) months. The primary end point of time to death or HFH was significantly lower in the LBBP group compared with BiVP (8% vs 28%; hazard ratio [HR], 0.26; 95% CI, 0.12-0.57; P < .001). There was no significant difference in all-cause mortality between the groups (2.0% vs 5.0%; HR, 0.40; 95% CI, 0.08-2.04; P = .25). However, LBBP significantly reduced the risk of HFH (7.0% vs 28.0%; HR, 0.23; 95% CI, 0.10-0.52; P < .001). The echocardiographic response rates were similar in both groups (86.0% vs 81.0%; P = .34) but the super-response rate was higher in the LBBP group (55.0% vs 36.0%; P < .007). Conclusions and Relevance In this study, LBBP was superior to BiVP in reducing the risk of death or HFH in patients with LBBB and severely reduced LVEF. Further trials are warranted in this patient population. Trial Registration Chinese Clinical Trial Registry identifier: ChiCTR2000036554

BACKGROUND:Right ventricular pacing (RVP) is associated with an increased risk of pacing-induced cardiomyopathy (PICM) in patients with a high pacing burden. Left bundle branch pacing (LBBP), a more physiological pacing modality, may better preserve cardiac function. OBJECTIVES:This randomized trial aimed to evaluate the clinical outcomes of LBBP vs RVP in patients with a high pacing burden with high risk of cardiac dysfunction. METHODS:In this prospective, multicenter, randomized controlled trial, 160 patients with a high pacing burden with high risk of cardiac dysfunction were randomly assigned in a 1:1 ratio to either LBBP or RVP. The primary endpoint was a composite of all-cause mortality, heart failure hospitalization, or PICM. Secondary endpoints were the individual components of the primary endpoints, echocardiographic parameters, and NYHA functional class. RESULTS:During a median follow-up duration of 36 months, the primary endpoint occurred in 9 patients in the LBBP group and in 25 patients in the RVP group (11.6% vs 33.9%; HR: 0.310; 95% CI: 0.145-0.664; P = 0.001), mainly driven by PICM (6.5% vs 18.2%; subdistribution HR: 0.324; 95% CI: 0.119-0.883; P = 0.028). No significant differences were observed in all-cause mortality (P = 0.391) and heart failure hospitalization (P = 0.100) between 2 groups. LBBP showed superior improvements over RVP in left ventricular ejection fraction (mean difference: 5.34; 95% CI: 3.18-7.50; P < 0.001), left ventricular end-diastolic diameter (mean difference: -3.06; 95% CI: -4.38 to -1.73; P < 0.001), and left ventricular end-systolic diameter (mean difference: -3.74; 95% CI: -5.07 to -2.41; P < 0.001) from baseline to 36 months. Patients in the LBBP group also showed favored NYHA functional class compared with those in the RVP group at the 36-month follow-up (1.66 ± 0.60 vs 1.90 ± 0.56, P = 0.014). CONCLUSIONS:In patients with a high pacing burden with high risk of cardiac dysfunction, LBBP significantly reduced the risk of the composite outcome, driven primarily by a decreased risk of PICM, and is associated with better echocardiographic improvements and clinical function. (A multicenter, prospective, randomized, controlled trial of left bundle branch pacing and right ventricular pacing in preventing deterioration of cardiac function in patients with ventricular pacing dependence [LBBP-FAVOUR]; ChiCTR2000036553).

Importance:Left bundle-branch pacing (LBBP) has been proposed as an alternative to biventricular pacing (BiVP) for patients with heart failure with left bundle-branch block (LBBB). However, robust clinical evidence from randomized clinical trials is lacking. Objective:To evaluate the long-term clinical outcomes of LBBP and BiVP. Design, Setting, and Participants:This multicenter, prospective, randomized clinical trial enrolled 200 patients at 6 centers in China with a left ventricular ejection fraction (LVEF) of 35% or less and LBBB from October 2020 to March 2022. This study was took place from October 2020 to September 2024. These data were analyzed September 2024 to December 2024. Interventions:Patients were randomly assigned in a 1:1 ratio to receive either LBBP or BiVP. Main Outcomes and Measures:The primary end point was the time to death from any cause or heart failure hospitalization (HFH). The secondary end points included all-cause death, HFH, echocardiographic response (absolute increase in LVEF ≥5%), and super response (absolute increase in LVEF ≥15% or improvement of LVEF to ≥50%) rates. Results:Of the 200 included patients, 136 were male and 64 were female. The success rate was 98% in the LBBP group and 94% in the BiVP group (P = .28). The median follow-up duration was 36 (range, 33-39) months. The primary end point of time to death or HFH was significantly lower in the LBBP group compared with BiVP (8% vs 28%; hazard ratio [HR], 0.26; 95% CI, 0.12-0.57; P < .001). There was no significant difference in all-cause mortality between the groups (2.0% vs 5.0%; HR, 0.40; 95% CI, 0.08-2.04; P = .25). However, LBBP significantly reduced the risk of HFH (7.0% vs 28.0%; HR, 0.23; 95% CI, 0.10-0.52; P < .001). The echocardiographic response rates were similar in both groups (86.0% vs 81.0%; P = .34) but the super-response rate was higher in the LBBP group (55.0% vs 36.0%; P < .007). Conclusions and Relevance:In this study, LBBP was superior to BiVP in reducing the risk of death or HFH in patients with LBBB and severely reduced LVEF. Further trials are warranted in this patient population. Trial Registration:Chinese Clinical Trial Registry identifier: ChiCTR2000036554.

BACKGROUND:Unexplained syncope and palpitations are common chief complaints in the outpatient department of cardiology. Their sporadic and unpredictable poses significant diagnostic challenges. Implantable cardiac monitors (ICMs) can monitor arrhythmia events efficiently, and can overcome the shortcomings of traditional electrocardiogram (ECG) detection tools such as Holter. However, the high cost of imported ICM devices limits accessibility for patients in China. The MA01-100 (Singular Medical, Suzhou, China), the first domestically developed ICM, may offer a cost-effective alternative. This study aimed to evaluate the safety and efficacy of the MA01-100 compared with standard surface electrocardiography (ECG) for arrhythmia monitoring in Chinese patients. METHODS:A prospective, paired design trial was conducted across six hospitals in China. Sixty-four participants underwent implantation of the MA01-100 ICM device. As the self-control group, patients were also assessed using a surface ECG at implantation, and 30- and 90-day follow-ups. The primary efficacy endpoints were the sensitivity and positive predictive value (PPV) of R wave detection at 30 days post-implantation. Secondary endpoints included R wave amplitude stability, QRS complex morphology consistency, arrhythmia event detection rate, arrhythmia event identification accuracy, clinical performance evaluation of the programmer, and remote transmission function assessment. Safety was evaluated by the incidence rates of major adverse events (MAEs), serious adverse events (SAEs), and device defects within 3 months of follow-up. RESULTS:All 64 patients who met the inclusion criteria were enrolled in the trial. They underwent successful cardiac monitor implantation with acceptable sensitivity and PPV of R wave detection. The mean sensitivity was 99.98 ± 0.10%, with a minimum of 99.34%. The two-sided 95% confidence interval (CI) for the compliance rate was (94.40%-100.00%). The mean PPV was 99.94 ± 0.35%, with a minimum of 97.35%. The two-sided 95% CI for the compliance rate was (94.40%-100.00%). Two patients (3.1%) experienced mild implantation site infections; no device defects or SAEs were observed. All pre-defined efficacy and safety benchmarks were met. CONCLUSION:This study provides the first prospective, multicenter clinical evaluation of the safety and efficacy of an intracardiac monitor (ICM) independently developed in China. It systematically validated the device's clinical performance, thereby filling the gap in China's ICM field across the entire chain of "independent development-clinical validation-translational application." The results demonstrate that the ICM meets the requirements for clinical use, providing new support for improving the accessibility of arrhythmia diagnostic services in China and offering a reference for formulating globally cost-effective cardiac monitoring strategies.

Background:Left bundle branch area pacing (LBBAP) emerges as an alternative to traditional right ventricular pacing, demonstrating safety and feasibility through superior access for implantation. Case summary:An 89-year-old female, with a prior history of pacemaker pocket infection and a tricuspid endocarditis during follow-up, was referred to our hospital for management due to a sinus arrest. The patient underwent pacemaker removal due to a pocket infection in the right subclavian area, necessitating tricuspid valvuloplasty for infective endocarditis. Venography revealed occlusion in the left brachiocephalic vein. Subsequently, LBBAP pacemaker implantation via the right iliac vein was performed, with follow-up indicating proper functioning of the pacing system. Discussion:The feasibility of the right iliac vein access for LBBAP implantation is highlighted, demonstrating good stability and offering a practical alternative. This approach mitigates unnecessary risks associated with thoracotomy and epicardial lead placement, providing a safer and effective option for cardiac pacing.

Considering the variability of amplitude and phase patterns in electrocardiogram (ECG) signals due to cardiac activity and individual differences, existing entropy-based studies have not fully utilized these two patterns and lack integration. To address this gap, this paper proposes a novel fusion entropy metric, morphological ECG entropy (MEE) for the first time, specifically designed for ECG morphology, to comprehensively describe the fusion of amplitude and phase patterns. MEE is computed based on beat-level samples, enabling detailed analysis of each cardiac cycle. Experimental results demonstrate that MEE achieves rapid, accurate, and label-free localization of abnormal ECG arrhythmia regions. Furthermore, MEE provides a method for assessing sample diversity, facilitating compression of imbalanced training sets (via representative sample selection), and outperforms random pruning. Additionally, MEE exhibits the ability to describe areas of poor quality. By discussing, it proves the robustness of MEE value calculation to noise interference and its low computational complexity. Finally, we integrate this method into a clinical interactive interface to provide a more convenient and intuitive user experience. These findings indicate that MEE serves as a valuable clinical descriptor for ECG characterization. The implementation code can be referenced at the following link: https://github.com/fdu-harry/ECG-MEE-metric.

Background: Cardiac resynchronization therapy (CRT) nonresponders account for nearly 30% of CRT candidates. Left-bundle branch pacing (LBBP) is an alternative to CRT. Objectives: This study aimed to evaluate the feasibility, clinical efficacy, and outcomes of upgrading to LBBP in CRT nonresponders, using propensity-score matching (PSM) analysis. Methods: CRT nonresponders were defined as those with an implantable CRT-pacemaker or CRT-defibrillator for more than 12 months who remained nonresponsive (a decrease in left ventricular end-systolic volume of <15% or a left ventricular ejection fraction [LVEF] absolute increase of <5%) after optimal medical therapy and device optimization compared with baseline. In total, 145 CRT nonresponders were prospectively enrolled and randomly divided into 2 groups: upgraded to LBBP (n = 48), and continuing biventricular pacing (BVP) (control; n = 97). PSM was performed at a 1:1 ratio, and clinical evaluation and echocardiographic assessments were compared at baseline and follow-up in paired cohorts. The primary composite endpoint for clinical outcomes (heart failure-related rehospitalization events, all-cause death, or heart transplantation) was analyzed. Results: Successful upgrading to LBBP was achieved in 48/49 patients (97.96%), with a significant decrease in QRS duration (P < 0.001). In the paired LBBP group, LVEF significantly increased (baseline: 29.75% +/- 7.79%; 6 months: 37.78% +/- 9.25% [P < 0.001]; 12 months: 38.84% +/- 12.13% [P < 0.001]) with 21/44 patients (47.73%) classified as echocardiographically responsive, whereas in the BVP control group, no significant improvement was observed (29.55% +/- 6.74% vs 29.22% +/- 8.10%; P = 0.840). In a multivariate logistic regression model, LV end-diastolic volume and baseline LBBB QRS morphology were independent predictors of echocardiographic response after upgrading to LBBP. At a median 24 months, the primary composite endpoint was significantly lower in the LBBP group (HR: 0.31; 95% CI: 0.14-0.72; log-rank P = 0.007). Conclusions: Upgrading to LBBP is feasible and effective in achieving significant heart function improvement and better clinical outcomes in CRT nonresponders, making it a reasonable and promising pacing strategy. (LBBP in CRT Non-Response patients; ChiCTR1900028131).

Background:Cardiac resynchronization therapy (CRT) has been shown to benefit patients with heart failure and left bundle branch block (LBBB). However, CRT implantation is challenging when the superior venous access is not feasible. Case summary:A 50-year-old man with a history of dilated cardiomyopathy and complete LBBB was referred to our hospital for CRT management. Angiography showed that the left and right brachiocephalic veins were occluded. Cardiac resynchronization therapy was finally implanted via the iliac vein. Follow-up echocardiography showed improved cardiac function, and the pacing system was functioning properly. Discussion:The iliac vein access is feasible for CRT implantation with good stability, which can be a viable alternative to avoid unnecessary risk associated with thoracotomy and epicardial lead placement.

Abstract: Studies have demonstrated the roles of trimetazidine beyond being an antianginal agent in ischemic heart disease (IHD) treatment associated with mechanisms of calcium regulation. Our recent studies revealed that mitochondrial calcium uniporter (MCU, the pore-forming unit responsible for mitochondrial calcium entrance) inhibition provided cardioprotective effects for failing hearts. Because trimetazidine and MCU are associated with calcium homeostasis, we hypothesized that trimetazidine may affect MCU to restore the failing heart function. In the present study, we tested this hypothesis in the context of cardiac ischemia in vivo and in vitro. The IHD model was established in male C57BL/6 mice followed by trimetazidine administration intraperitoneally at 20 mg/kg q.o.d for 8 weeks. In vitro studies were performed in a hypoxia model using primary rat neonate cardiomyocytes. The mice survival outcomes and heart function, pathohistologic, and biological changes were analyzed. The results demonstrated that trimetazidine treatment resulted in longer life spans and heart function improvement accompanied by restoration of mitochondrial calcium levels and increase in ATP production via MCU down-regulation. Studies in vitro further showed that trimetazidine treatment and MCU inhibition decreased reactive oxygen species (ROS) production, inhibited the NFκB pathway, and protected the cardiomyocytes from hypoxic injury, and vice versa. Thus, the present study unveils a unique mechanism in which trimetazidine is involved in ameliorating the ischemic failing heart via MCU down-regulation and the following mitochondrial calcium homeostasis restoration, ROS reduction, and cardiomyocyte protection through NFκB pathway inhibition. This mechanism provides a novel explanation for the treatment effects of trimetazidine on IHD.

BACKGROUND: Left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT) has shown encouraging results for QRS duration reduction and heart function improvement. However, the feasibility and efficacy of LOT-CRT have not been well established in intraventricular conduction delay patients. This study aims to assess and compare the efficacy and clinical outcome of CRT based on left bundle branch pacing, combined with coronary sinus left ventricular pacing (LOT-CRT) with CRT via biventricular pacing (BiV-CRT) in intraventricular conduction delay patients indicated for CRT. METHODS: Consecutive patients with intraventricular conduction delay and CRT indications were assigned nonrandomized to LOT-CRT (n=30) or BiV-CRT (n=55). Addition of the left bundle branch pacing (or coronary venous) lead was at the discretion of the implanting physician guided by suboptimal paced QRS complex and on clinical grounds. Echocardiographic parameters and clinical characteristics were accessed at baseline and during 2-years’ follow-up. RESULTS: Success rate for LOT-CRT and BiV-CRT was 96.8% and 96.4%. LOT-CRT had greater reduction of QRS duration compared with BiV-CRT (42.7±17.4 ms versus 21.9±21.5 ms; P <0.001). Higher left ventricular ejection fraction was also achieved in LOT-CRT than BiV-CRT at 6-month (36.7±9.8% versus 30.5±6.4%; P <0.05), 12-month (34.8±7.6% versus 30.3±6.2%; P <0.05), 18-month (36.3±7.9% versus 28.1±6.6%; P <0.005), and 24-month follow-up (37±9.5% versus 30.5±7%; P <0.05). Adverse clinical outcomes including heart failure rehospitalization and mortality were lower in LOT-CRT group for 24 months follow-up (hazard ratio, 0.33; P =0.035). CONCLUSIONS: LOT-CRT improves ventricular electrical synchrony and may provide greater clinical outcomes as compared with BiV-CRT in intraventricular conduction delay patients. These findings need further evaluation in future randomized controlled trials.

传统心脏起搏器通常通过锁骨下静脉入路植入。由于对导线的长度需求、递送系统长度限制以及髂静脉穿刺和囊袋制作流程顾虑，甚少选择髂静脉入路。本文拟介绍本中心经髂外静脉途径分别植入双腔起搏器和三腔起搏器的2个病例及其随访结果。

Subcutaneous implantable cardioverter–defibrillators (S-ICDs) have been shown to be non-inferior to transvenous ICDs in the prevention of sudden cardiac death (SCD), but there is still a lack of evidence from clinical trials in China. We investigated whether S‑ICD implantation in the Chinese population is safe and feasible and should be promoted in the future. Consecutive patients undergoing S‑ICD implantation at our center were enrolled in this retrospective study. Data were collected within the median follow-up period of 554 days. Data concerning patient selection, implantation procedures, complications, and episodes of shock were analyzed. In total, 70.2

Dilated cardiomyopathy(DCM)is a primary myocardial disease of unknown cause that is characterized by ventricular enlargement and ventricular systolic dysfunction(Reichart et al.,2019).DCM exhibits obvious heterogeneity,and its outcomes extend from arrhythmia to heart failure.Early arrhythmia is a common condition that may pro-gressively become aggravated,and death can occur at any stage of the disease.The most serious complications are heart failure and sudden death(McNally et al.,2013).

BackgroundMonitoring of lead depth is crucial to achieve left bundle branch pacing (LBBP) with a low capture threshold and avoid septal perforation, but lacks informative approach.ObjectiveWe aimed to prospectively assess the predictive value of current of injury on the occurrence of inadequate left bundle branch (LBB) capture threshold and acute septal perforation.MethodsConsecutive patients who received LBBP were enrolled. ST-segment elevation ≥ 25% of intrinsic R-wave amplitude on the unipolar intracardiac electrogram was defined as a sign of distinct current of injury. An LBB capture threshold of <1.5 V/0.5 ms was considered acceptable.ResultsLBBP was attempted 513 times in 212 patients. The LBB capture threshold was more likely to improve to an acceptable level after 10 minutes in leads with initial (33 of 47 vs 0 of 8, with vs without) and residual (29 of 33 vs 4 of 14, with vs without) current of injury recorded on the tip electrode (P < .0001). Lead perforation during the procedure has occurred in 11 patients who had no current of injury noted on the tip electrode. The ratio of current of injury recorded on the tip electrode to that on the ring electrode was correlated to the lead depth determined by sheath angiography (Spearman correlation coefficient −0.624; P < .0001), and microperforation is highly possible when the ratio is decreased to <1 (sensitivity 100%; specificity 96.6%).ConclusionCurrent of injury is a useful tool in forecasting LBBP lead depth and septal perforation, and it could facilitate the decision-making process when the initial LBB capture threshold is undesirable.

Objectives: The purpose of our study was to evaluate the feasibility and efficacy of cardiac resynchronization therapy (CRT) via left bundle branch pacing (LBBP-CRT) compared with optimized bi-ventricular pacing (BVP) with adaptive algorithm (BVP-aCRT) in heart failure with reduced left ventricular ejection fraction≤35% (HFrEF) and left bundle branch block (LBBB). Methods: One hundred patients with HFrEF and LBBB undergoing CRT were prospectively enrolled in a non-randomized fashion and divided into 2 groups (LBBP-CRT, n=49; BVP-aCRT, n=51) in 4 centers. Implant characteristics and echocardiographic parameters were accessed at baseline and during 6-month and 1-year follow-up. Results: The success rate for LBBP-CRT and BVP-aCRT was 98.00% and 91.07 %. Fused LBBP had the greatest reduced QRS duration compared to BVP-aCRT (102.61±9.66ms vs 126.54±11.67ms, P<0.001). Higher absolute LVEF and ΔLVEF was also achieved in LBBP-CRT than BVP-aCRT at 6-month (P=0.008,P=0.020) and 1-year follow-up (P=0.021,P=0.015). There was no significant difference in response rate between two groups while higher super-response rate was observed in LBBP-CRT as compared to BVP-aCRT at 6-month(53.06% vs 36.59%, p=0.016) and 12-month(61.22% vs 39.22%, p=0.028) during follow-up. The pacing threshold was lower in LBBP-CRT at implant and during 1-year follow-up(both p<0.001). Procedure-related complications and adverse clinical outcomes including heart failure hospitalization and mortality were not significantly different in 2 groups. Conclusions: The feasibility and efficacy of LBBP-CRT demonstrated better electromechanical resynchronization and higher clinical and echocardiographic response, especially higher super-response than BVP-aCRT in HFrEF with LBBB.

Electrocardiogram (ECG), a technique for medical monitoring of cardiac activity, is an important method for identifying cardiovascular disease. However, analyzing the increasing quantity of ECG data consumes a lot of medical resources. This paper explores an effective algorithm for automatic classifications of multi-classes of heartbeat types based on ECG. Most neural network based methods target the individual heartbeats, ignoring the secrets embedded in the temporal sequence. And the ECG signal has temporal variation and unique individual characteristics, which means that the same type of ECG signal varies among patients under different physical conditions. A two-stream architecture is used in this paper and presents an enhanced version of ECG recognition based on this. The architecture achieves classification of holistic ECG signal and individual heartbeat and incorporates identified and temporal stream networks. Identified networks are used to extract features of individual heartbeats, while temporal networks aim to extract temporal correlations between heartbeats. Results on the MIT-BIH Arrhythmia Database demonstrate that the proposed algorithm performs an accuracy of 99.38\%. In addition, the proposed algorithm reaches an 88.07\% positive accuracy on massive data in real life, showing that the proposed algorithm can efficiently categorize different classes of heartbeat with high diagnostic performance.

Objective:To investigate the incidence and clinical characteristics of femoral vein thrombus after leadless pacemaker implantation.Methods:The patients received leadless pacemaker implantation in Zhongshan Hospital, Fudan University from April 2020 to January 2021 were consecutively included. All of the patients suffered from bradycardia were indicated for a single chamber pacemaker implantation and received femoral vein ultrasound at the first day post-procedure. The incidence and the clinical characteristics were described and the correlation factors were analyzed.Results:One hundred and forty-six patients were enrolled. The incidence of femoral vein thrombus was 2.74% (4/146). The average age of these 4 cases was (75.75±19.14) years old with 3 males,and all the patients were asymptomatic. During follow-up, there were no adverse outcomes happened, including thromboembolism with the thrombus. The femoral vein thrombus of 3 cases disappeared at 1 month's follow-up, and 1 case disappeared at 2 months post-procedure. In thrombus group, elevation of D-dimmer (>0.5 mg/L) were documented in 1 case (25.00%) pre-procedure, and 3 cases (75.00%) post-procedure while the median level of D-dimmer pre-procedure were not significantly different as compared to post-procedure [0.33(0.26,0.94) mg/L vs.1.49(0.67,2.17) mg/L,P=0.057)].The occurrence of femoral vein thrombus after leadless pacemaker implantation was significantly associated with D-dimmer elevation post-procedure by Spearman correlation analysis (r=0.239,P=0.037). While it was not significantly correlated to the other factors including age, gender, body weight, comorbidities (atrial fibrillation, hypertension and diabetes), baseline echocardiographic parameters, D-dimmer elevation pre-procedure, fluoroscopic time and closure methods (all P>0.05).Conclusion:The incidence of femoral vein thrombus was rather low. Monitoring D-dimmer and performing puncture site ultrasound post-procedure are helpful to detect femoral vein thrombus and start anticoagulation in time.

Objectives: To compare electromechanical ventricular synchrony when pacing from different sites including right ventricular apex pacing (RVAP), right ventricular septum pacing (RVSP), His Bundle pacing (HBP), left bundle branch pacing (LBBP) and RVSP during unipolar pacing from the ring electrode of LBBP lead (RVSPring ) in each patient. Methods: Twenty patients with complete atrioventricular block (AVB) indicated for dual-chamber pacemaker implantation were included. Unipolar pacing at different sites including RVAP, RVSP，HBP，LBBP and RVSPring were successively performed. Pacing characteristics and echocardiogram parameters were compared among intrinsic rhythm and pacing at different sites. Results: Similar to HBP(114.84 ±18.67ms), narrower paced QRSd was found in LBBP(116.15±11.60ms) versus RVSPring(135.11±13.68ms), RVSP(141.75±14.08ms) and RVAP(158.15±21.41ms)(p＜0.001). LBBP showed comparable pacing parameters to RVAP or RVSP and were significantly better than HBP, with maintained cardiac function. TS-12-SD was significantly improved in LBBP(27.00±21.53ms) than RVAP(54.05±34.21ms, p=0.004) and RVSP(47.56±33.26ms, p=0.029) but similar to HBP(37.05±26.24ms, p=0.283) or RVSPring(42.16±26.19ms, p=0.107). Negative values of interventricular mechanical delay(IVMD) were only identified in LBBP(-20.16±18.47ms), significantly different from RVAP(33.68±30.98ms), RVSP (21.68±22.02ms), HBP (4.74±19.04ms) and RVSPring(14.56±26.76ms(all p＜0.001). Using Pearson’s analysis, Sti-LVAT was positively corelated with QRS, IVMD, TS-12-SD, LVEDV and LVESV while a negative relationship was identified for LVEF. Conclusions: Similar to HBP, LBBP achieved better electrical and mechanical left ventricular synchrony than conventional RV pacing. For interventricular synchrony, only LBBP initiated earlier LV activation than RV among these pacing strategies, in consistent with the RBBB pattern of paced QRS during LBBP.