Evaluation of Accelerated Bachmann Bundle Area Pacing in Heart Failure With Reduced ejectIon Fraction Who Have electrocarDioGraphic Evidence of Interatrial Block and Indicated for Implantable Cardioverter Defibrillator

Interatrial block (IAB) is a distinct electrocardiographic finding resulting from delayed conduction between the right and left atria through Bachmann's bundle (BB). In a prevalence study of non-hospitalized individuals aged 65 years or older in sinus rhythm, IAB was observed in 59% of participants. With population aging and improved survival among patients with cardiovascular comorbidities, the prevalence of IAB is expected to increase further. Importantly, IAB leads to delayed left atrial contraction and impaired left ventricular diastolic filling, pathophysiological features commonly observed in heart failure (HF) that contribute to worsening HF symptoms. Bachmann bundle area pacing (BBAP) has emerged as an attractive alternative to conventional right atrial appendage (RAA) pacing. Recent studies have demonstrated that BBAP, when guided by intracardiac electrograms and implemented using sheath-assisted atrial lead implantation techniques, is a safe and feasible approach for effectively correcting IAB. Echocardiographic data have shown that BBAP induces biatrial resynchronization. In clinical studies involving patients with heart failure with preserved ejection fraction (HFpEF), BBAP has been associated with significant clinical benefits, including improvements in quality of life, increased physical activity, and reductions in NT-proBNP levels. In these HFpEF studies, the clinical effects of BBAP were evaluated using physiologically accelerated pacing (approximately 70 beats per minute or individualized fine-tuned accelerated pacing based on body size and left ventricular ejection fraction), with particularly notable benefits observed in the improvement of diastolic function. Despite these promising findings, the role of BBAP and BBAP-mediated accelerated pacing in patients with heart failure with reduced ejection fraction (HFrEF) has not yet been clearly established. In animal (porcine) models, improvement in atrial synchrony achieved through BBAP has been shown to significantly increase left ventricular stroke volume compared with conventional RAA pacing, as confirmed by comprehensive hemodynamic analyses. However, despite the potential advantages of this more physiological pacing strategy, human data evaluating BBAP in patients with HFrEF remain limited. Accordingly, the present study aims to evaluate the clinical effects of atrial resynchronization achieved through accelerated BBAP in patients with HFrEF accompanied by interatrial block who meet indications for implantable cardioverter-defibrillator implantation.