CRT Improves Outcome in Pacing-Dependent Patients With Depressed EF

Typically, patients with atrioventricular (AV) block who receive right ventricular pacing are able to achieve an adequate heart rate. However, there is increasing concern that right ventricular apical pacing may lead to progressive left ventricular systolic dysfunction and heart failure. Some experts believe that biventricular pacing with standard cardiac-resynchronization therapy (CRT) may circumvent this problem. Previous CRT studies have examined advanced systolic heart failure but excluded patients with moderate-to-high AV block who require pacing. The present study sought to examine the effect of biventricular pacing in patients with AV block, mild-to-moderate heart failure, and abnormal left ventricular systolic function. The investigators hypothesized that right ventricular pacing may promote electrical and mechanical dyssynchrony, while biventricular pacing may reduce morbidity, mortality, and adverse left ventricular remodeling.

Curtis and colleagues conducted a prospective, multicenter, randomized, double-blind trial, the Biventricular Versus Right Ventricular Pacing in Heart Failure Patients With Atrioventricular Block (BLOCK HF) study. The study criteria included an indication for ventricular pacing with AV block, left ventricular ejection fraction ≤ 50%, and mild-to-moderate heart failure. Of the 918 BLOCK HF patients, 691 received a CRT pacemaker or implantable cardioverter-defibrillator (ICD) and underwent randomization to receive standard right ventricular pacing or biventricular pacing. The average follow-up was 37 months.

Study findings revealed that the primary outcome (time to death from any cause, an urgent care visit for heart failure, or a ≥ 15% increase in the left ventricular end-systolic volume index) occurred in 190 of 342 patients (55.6%) in the right ventricular group compared with 160 of 349 (45.8%) in the biventricular group. Specifically, patients randomized to receive biventricular pacing showed a significantly lower incidence of urgent care visits for heart failure, death from any cause, or progression of heart failure over time than did patients who underwent right ventricular pacing (hazard ratio = 0.74; 95% credible interval, 0.60–0.90). Similar results were found in the CRT pacemaker and ICD groups. Complications attributed to left ventricular lead occurred in 6.4% of patients.

The researchers concluded that pacing both ventricles in patients with AV block and left ventricular systolic dysfunction is significantly more beneficial to patients than the conventional method of pacing the right ventricle alone. They noted that patients enrolled in their BLOCK HF trial who underwent biventricular pacing had a lower incidence of urgent care visits for heart failure, death from any cause, or progression of heart failure. Curtis and colleagues suggest that biventricular pacing in patients with AV block preserves systolic function. The authors emphasized that research is needed to determine the best pacing options for patients with AV block and an abnormal left ventricular ejection fraction.