Biventricular vs. Right Ventricular Pacing Outcomes

Study Questions:

What were the clinical outcomes in terms of clinical composite score (CCS), quality of life (QOL), and change in New York Heart Association (NYHA) classification in patients in the BLOCK HF (Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block) trial?


The BLOCK HF trial randomized patients with atrioventricular block, NYHA symptom class I-III heart failure, and left ventricular ejection fraction (LVEF) ≤50% to biventricular or right ventricular (RV) pacing. NYHA classification, QOL, and CCS were assessed at 6, 12, 18, and 24 months. Bayesian statistical methods were employed, with prespecified metric of benefit being a posterior probability of ≥0.95%.


Patients with biventricular pacing showed greater improvement in NYHA class at 12 months, with 19% improved, 61% unchanged, and 17% worsened, compared to 12%/62%/23% in the RV arm. QOL was improved through 12 months. At 6 months, CCS was improved/unchanged/worsened in 53%/24%/24% in the biventricular arm compared to 39%/33%/28% in the RV arm. This improvement in CCS was sustained through 24 months.


The authors concluded that 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 to RV pacing.


The BLOCK HF trial is the largest published trial comparing RV and biventricular pacing modes in patients with an indication for pacing and evidence that they would require frequent ventricular pacing and an LVEF of ≤50%. The study had a heterogeneous population with 30% of the participants with LVEF <35%, and a similar percentage had NYHA class III. These patients would already be expected to benefit from biventricular pacing extrapolating from other trials. For patients with LVEF between 35% and 50%, the benefit of biventricular pacing is less well established. The present study attempts to provide a more detailed account of the clinical benefits of the entire trial population using the Packer CCS, QOL, and NYHA class. A publication of an even larger study (BIOPACE), examining outcomes of biventricular pacing versus RV pacing in patients requiring frequent ventricular pacing, is still pending.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure

Keywords: Arrhythmias, Cardiac, Atrioventricular Block, Cardiac Resynchronization Therapy, Heart Failure, Outcome Assessment (Health Care), Pacemaker, Artificial, Quality of Life, Risk, Secondary Prevention, Stroke Volume, Ventricular Function, Left

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