Bachmann Bundle Pacing for Prevention of New-Onset Atrial Fibrillation in Patients With Heart Failure

Background Chronic heart failure (HF) is a prevalent and prognostically poor cardiovascular disorder, with atrial fibrillation (AF) being the most common arrhythmia comorbid with HF. The bidirectional interaction between HF and AF forms a vicious cycle, significantly elevating the risks of mortality, hospitalization, and stroke in affected patients. Epidemiological data indicate that the cumulative incidence of AF following pacemaker implantation reaches 30-40%, a rate markedly higher than that in the general population without pacemaker implantation.

Traditional right atrial appendage (RAA) pacing, the most widely used clinical atrial pacing approach, induces prolonged interatrial conduction, asynchronous atrial contraction, and hemodynamic perturbations, which predispose patients to AF. The Bachmann bundle represents the most physiological atrial pacing site; pacing in this region achieves synchronous activation of the left and right atria, producing a narrower P wave compared with sinus rhythm and traditional RAA pacing. While prior studies have suggested that Bachmann bundle pacing (BBP) may reduce the recurrence and progression of atrial arrhythmias, there remains a paucity of prospective randomized controlled trials investigating the efficacy of BBP in preventing new-onset AF in HF patients undergoing cardiac resynchronization therapy with left bundle branch pacing (CRT/LBBP) or implantable cardioverter defibrillator (ICD) implantation.

Study Objectives The primary objective of this study is to determine whether BBP reduces the incidence of new-onset AF within 12 months of device implantation, compared with traditional RAA pacing, in HF patients with indications for CRT/LBBP or ICD implantation. Secondary objectives include evaluating the impact of BBP on the time to first new-onset AF, procedural safety, cardiac function parameters, electrophysiological indices, and clinical adverse events (including HF rehospitalization, all-cause death, and stroke) during the 12-month follow-up period.

Study Procedures

1. Screening and Baseline Assessment Eligible patients are identified per predefined inclusion and exclusion criteria. Following written informed consent, baseline data are collected, including demographic characteristics, medical history, 12-lead electrocardiogram (ECG), 24-hour Holter monitoring, transthoracic echocardiography, New York Heart Association (NYHA) functional classification, 6-minute walk test results, and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels. 2. Randomization Patients are stratified by implant device type (CRT/LBBP or ICD) and randomized in a 1:1 ratio to the BBP group or the RAA pacing group via a central randomization system. 3. Intervention Patients in the BBP group undergo atrial lead implantation at the Bachmann bundle region, identified via anatomical localization and intracardiac electrogram recording. Successful BBP is defined by characteristic ECG changes: a positive P wave in leads I, II, III, and aVF; a biphasic or negative P wave in lead V1; a P wave duration narrowed by \>10 ms compared with baseline (in patients with pre-existing interatrial block); and documentation of the Bachmann bundle potential. If BBP implantation fails, the patient is immediately converted to RAA pacing, with the cause of failure recorded in detail. Intraoperative pacing parameters (threshold, sensing, impedance) are monitored in both groups. 4. Follow-up All patients undergo follow-up assessments at 1 week, 3 months, 6 months, 9 months, and 12 months post-implantation. Follow-up evaluations include ECG, 24-hour Holter monitoring, pacemaker programming, echocardiography, NYHA classification reassessment, 6-minute walk test, NT-proBNP measurement, medication adjustment tracking, and adverse event reporting. 5. Statistical Analysis All data are analyzed in accordance with the intention-to-treat (ITT) principle. The primary endpoint is compared using analysis of covariance, and the time to first new-onset AF is evaluated via the Kaplan-Meier method with log-rank testing. Continuous variables are compared using the t-test or Wilcoxon rank-sum test, while categorical variables are analyzed with the chi-square test or Fisher's exact test. A two-sided P value \< 0.05 is considered statistically significant.

• Immediate Success Rate of Bachmann Bundle Pacing and Perioperative Complication Rate [Time frame: Intraoperatively (success rate) and 30 days post-implantation (perioperative complications)]
• Absolute and percentage change in left atrial diameter/volume index from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Change in mitral/tricuspid regurgitation grade from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Absolute change in left ventricular end-diastolic diameter (LVEDD) from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Absolute change in left ventricular end-systolic volume (LVESV) from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Change in New York Heart Association (NYHA) functional class from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Absolute change in 6-minute walk test (6MWT) distance from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Absolute change in plasma NT-ProBNP level from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Comparison of P-wave duration from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Comparison of P-wave amplitude from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Comparison of P-wave vector from baseline to 12 months [Time frame: Baseline and 12 months after device implantation]
• Prevalence of interatrial block at baseline and 12 months [Time frame: Baseline and 12 months after device implantation]