Comparison of left bundle branch area pacing and biventricular pacing for atrioventricular block with heart failure and mild-to-moderately reduced left ventricular systolic function: design and rationale of the BLOCK NAGOYA randomized clinical trial

Background: Cardiac resynchronization therapy (CRT) with biventricular pacing (BVP) is an established cardiac physiologic pacing strategy for patients requiring substantial ventricular pacing, heart failure (HF), and reduced left ventricular ejection fraction (LVEF). Recently, left bundle branch area pacing (LBBAP) has emerged as a promising alternative to BVP. It remains uncertain whether BVP or LBBAP is more advantageous for patients with mild-to-moderately reduced left ventricular systolic function. Objective: To compare efficacy and safety of LBBAP and BVP in patients with atrioventricular block and LVEF of 36-50%. Methods: The BLOCK NAGOYA trial is a multicenter, prospective, randomized, controlled trial to determine whether LBBAP is superior to BVP in terms in improving left ventricular function. A total of 46 participants, with advanced atrioventricular block, HF, and LVEF of 36-50%, will be recruited in 17 Japanese institutions and randomized to receive either LBBAP (with targeted left bundle branch capture) or BVP treatment arm. Results: The primary endpoint is the change in LVEF at 6 months. Secondary endpoints include changes in brain natriuretic peptide levels, electrocardiographic and echocardiographic findings at 6 months, clinical outcomes (hospitalization for HF or ventricular arrhythmias), and adverse events. The follow-up duration is set to two years after the implantation. Conclusion: The BLOCK NAGOYA trial will provide significant insights on the optimal physiologic pacing therapy for patients with atrioventricular block, HF, and mild-to-moderately reduced LVEF. Trial registration number: Japan Registry of Clinical Trials: jRCTs042240129: https://jrct.mhlw.go.jp/en-latest-detail/jRCTs042240129