Ventricular lead positioning within the left conduction system in permanent cardiac pacing: a systematic review and meta-analysis.

BACKGROUND: Left bundle branch pacing (LBBP) and left bundle fascicular pacing (LBFP) are conduction system pacing techniques that preserve physiological ventricular activation. Whether proximal or distal capture yields superior electrical or echocardiographic outcomes is uncertain. OBJECTIVE: To systematically evaluate and compare LBFP versus left bundle branch trunk pacing (LBBP) in terms of electrical synchrony and echocardiographic characteristics in patients requiring permanent cardiac pacing. METHODS: We searched PubMed, Embase, and Cochrane through May 21, 2025, for randomized and observational studies comparing LBFP with LBBP. Outcomes of interest included QRS duration, V6 R-wave peak time (RWPT), left ventricular activation time (LVAT), left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), and pacing thresholds. Statistical analysis was performed using a random-effects model, with heterogeneity assessed using I² statistics. Risk of bias was evaluated using the ROBINS-I. RESULTS: Six studies involving 2,989 patients (1,241 LBFP; 249 LBBP) were included. There were 3 prospective studies, 2 retrospective, and 1 that was both prospective and retrospective. There were no RCTs on this subject. LBFP was associated with a statistically shorter V6-RWPT (mean difference: − 3.50 ms; 95% CI: − 5.74 to − 1.26; p = 0.002), representing a modest electrophysiological difference without a corresponding difference in LVAT. No significant differences were observed in QRS duration, LVAT, LVEF, LVEDD, or pacing thresholds. Both modalities demonstrated high procedural success and low, stable capture thresholds. CONCLUSION: LBFP achieved faster ventricular activation compared with LBBP, while maintaining comparable mechanical performance and pacing stability. Its broader anatomical accessibility and favorable electrical profile support LBFP as a practical alternative particularly when proximal conduction capture is not feasible. Further randomized trials are warranted to assess long-term outcomes.