Improvement in Clinical Outcomes with Biventricular Versus Right Ventricular Pacing the BLOCK HF Study

Background Sustained right ventricular (RV) apical pacing may lead to deterioration in ventricular function and an increased risk of heart failure, especially in patients with pre-existing systolic dysfunction. The BLOCK HF (Biventricular Versus Right Ventricular Pacing in Heart Failure Patients With Atrioventricular Block) trial demonstrated that biventricular-paced patients had a reduced incidence of a composite endpoint of death, heart failure-related urgent care, and adverse left ventricular remodeling. Objectives In a pre-specified analysis, this study examined clinical outcomes, including clinical composite score, quality of life (QOL), and change in New York Heart Association (NYHA) functional classification. Methods The BLOCK HF trial randomized patients with atrioventricular block, NYHA symptom class I to III heart failure, and left ventricular ejection fraction ≤50% to biventricular or RV pacing. NYHA functional classification, QOL, and clinical composite score were assessed at 6, 12, 18, and 24 months. Bayesian statistical methods were used, with the pre-specified metric of benefit being a posterior probability ≥0.95. Results Patients with biventricular pacing showed greater improvement in NYHA functional class at 12 months, with 19% improved, 61% unchanged, and 17% worsened, compared with 12%/62%/23% in the RV arm. QOL was improved through 12 months. At 6 months, clinical composite score was improved/unchanged/worsened in 53%/24%/24% in the biventricular arm compared with 39%/33%/28% in the RV arm. This improvement in clinical composite score was sustained through 24 months. Conclusions For patients with atrioventricular block and systolic dysfunction, biventricular pacing not only reduces the risk of mortality/morbidity, but also leads to better clinical outcomes, including improved QOL and heart failure status, compared with RV pacing.