HeartSync Trial Compares Left Bundle Branch Pacing With Biventricular Pacing

Key Takeaways

• In this randomized clinical trial, left bundle-branch pacing was superior to biventricular pacing for reducing the composite risk of all-cause mortality or heart failure hospitalization in patients with heart failure, left bundle-branch block, and severely reduced left ventricular ejection fraction.
• The report also described device performance, reverse remodeling, and functional outcomes, with several measures favoring left bundle-branch pacing.
• Safety findings were reported within the same trial comparison, with no major complications observed in the left bundle-branch pacing group.

The comparison extended beyond procedural performance alone and included long-term clinical outcomes, device-related measures, echocardiographic remodeling, functional status, and safety events. Within that framework, the central finding was that left bundle-branch pacing was associated with better long-term clinical outcomes than biventricular pacing in the study population.

The study enrolled 200 patients at 6 centers in China with left bundle-branch block and a left ventricular ejection fraction of 35% or less. Patients were randomized 1:1 to receive either left bundle-branch pacing or biventricular pacing. The median follow-up duration was 36 months. This design placed the trial’s emphasis on long-term comparative outcomes in a defined cardiac resynchronization therapy population rather than on acute procedural differences alone. The primary endpoint was time to all-cause mortality or heart failure hospitalization.

Investigators reported that this composite outcome occurred less often in the left bundle-branch pacing group than in the biventricular pacing group (8% vs 28%; hazard ratio, 0.26; 95% CI, 0.12-0.57; P<.001). All-cause mortality alone did not differ significantly between groups (2.0% vs 5.0%; hazard ratio, 0.40; 95% CI, 0.08-2.04; P=.25). However, heart failure hospitalization was significantly less frequent with left bundle-branch pacing (7.0% vs 28.0%; hazard ratio, 0.23; 95% CI, 0.10-0.52; P<.001). The authors therefore interpreted left bundle-branch pacing as superior to biventricular pacing for the principal clinical outcome, with the difference driven mainly by fewer heart failure hospitalizations.

Researchers also reported device-performance findings within the randomized comparison. The initial implant success rate was 98% in the left bundle-branch pacing group and 94% in the biventricular pacing group. Paced QRS duration was shorter with left bundle-branch pacing, and pacing thresholds were lower both at implantation and at follow-up. These device-related findings were presented alongside the clinical outcomes rather than as isolated technical observations.

The evaluation also included echocardiographic remodeling and functional outcomes. Both groups improved, but changes in left ventricular ejection fraction, left ventricular end-diastolic diameter, and left ventricular end-systolic diameter favored left bundle-branch pacing. The echocardiographic response rate did not differ significantly between groups (86.0% vs 81.0%; P=.34), whereas the super-response rate was higher with left bundle-branch pacing (55.0% vs 36.0%; P=.007). Functional status also improved in both groups, with better New York Heart Association class at last follow-up in the left bundle-branch pacing group.

Safety events were reported within the overall trial readout. Investigators stated that there were no major complications in the left bundle-branch pacing group. In the biventricular pacing group, 1 lead dislodgement and 2 increases in pacing threshold were reported. Across the report, the randomized comparison therefore spans structural change, patient function, clinical outcomes, device performance, and safety observations, while supporting left bundle-branch pacing as the more favorable strategy in this study population.