LEFT VENTRICULAR REVERSE REMODELING WITH BIVENTRICULAR VERSUS RIGHT VENTRICULAR PACING IN PATIENTS WITH ATRIOVENTRICULAR BLOCK AND LEFT HEART FAILURE IN THE BLOCK HF TRIAL



Anne Curtis, M.D., University at Buffalo, Buffalo, NY, USA

Background: In patients with heart failure (HF), biventricular pacing (BIV) attenuates adverse left ventricular (LV) remodeling in addition to improving survival and relieving symptoms. However, little is known about the effects of BIV pacing in HF patients with atrioventricular (AV) block.

Methods: The BLOCK HF trial randomized patients with AV block, NYHA class I-III heart failure, and LV ejection fraction (EF) less than or equal to 50% to BIV or right ventricular (RV) pacing. Doppler echocardiograms (DE) were obtained at randomization (30-60 days post-implant) and at 6, 12, 18, and 24 months. Data analysis comparing changes in 10 pre-specified echo parameters over time was conducted using a Bayesian adaptive design and all objectives were evaluated with intention-to-treat analyses.

Results: There were 624 subjects among the 691 randomized subjects who had paired DE data for one or more analyses. LV volumes, EF, diastolic function and intra-ventricular mechanical delay (IVMD) were estimated at all time points. BIV pacing resulted in LV reverse remodeling, with significant reduction in LV end systolic and end diastolic volume indices and in IVMD and improvement in EF. By contrast, none of these parameters changed with RV pacing, indicating that no reverse remodeling occurred post-randomization.

Conclusions: Patients with AV block, depressed LV function, and HF symptoms benefit from BIV pacing with regard to cardiac structure and function. This DE analysis has important clinical implications in supporting the use of BIV pacing rather than RV pacing for patients with HF and AV block.