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 (LBTP) 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 LBTP. 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 I 2 statistics. Risk of bias was evaluated using the ROBINS-I. Results: Six studies involving 2,989 patients (1,241 LBFP; 249 LBTP) were included. LBFP was associated with a significantly shorter V6-RWPT (mean difference: –3.50 ms; 95% CI: –5.74 to –1.26; p=0.002), suggesting improved electrical synchrony. 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 LBTP, 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. Keywords: Conduction system pacing; left bundle branch pacing; fascicular pacing; ventricular synchrony; permanent pacemaker; meta-analysis; cardiac resynchronization Glossary of Abbreviations: CSP : Conduction system pacing; HBP : His bundle pacing; LBBAP : Left bundle branch area pacing; LBBP : Left bundle branch pacing (proximal/trunk); LBFP : Left bundle fascicular pacing; LBTP : Left bundle trunk pacing; LVAT : Left ventricular activation time; LVEDD : Left ventricular end-diastolic diameter; RWPT : R-wave peak time (lead V6); ROBINS-I : Risk of Bias in Non-Randomized Studies of Interventions; RoB 2 : Cochrane Risk of Bias 2.0 tool; PROSPERO : International Prospective Register of Systematic Reviews; NYHA : New York Heart Association (functional class).