Biventricular pacing best in atrioventricular block patients

By Eleanor McDermid, Senior medwireNews Reporter

Use of biventricular rather than conventional right ventricular pacing results in better clinical outcomes in patients who have heart failure with atrioventricular block and left ventricular systolic dysfunction, show the results of BLOCK HF.

"These findings address the clinical need to determine the best possible pacing mode for patients with atrioventricular block and an abnormal left ventricular ejection fraction who do not have an established indication for biventricular pacing," write the researchers in The New England Journal of Medicine.

The randomized controlled trial included 691 patients who were followed up for the primary composite outcome of death, an urgent care visit for heart failure, or an increase in the left ventricular end-systolic volume index of at least 15%. During follow up lasting an average of 37 months, this occurred in 45.8% of patients who received biventricular pacing, compared with 55.6% of those given right ventricular pacing, which was a significant difference.

Most endpoints related to urgent care or left ventricular end-systolic volume index; treatment allocation did not influence mortality risk over the period studied.

Previous trials excluded patients who had atrioventricular block and required right ventricular pacing, in order to determine the benefits of cardiac-resynchronization therapy without the confounding effects of right ventricular pacing. It was thought that right ventricular pacing may lead to progressive left ventricular dysfunction.

"This study adds to the body of evidence suggesting that biventricular pacing in patients with atrioventricular block preserves systolic function," comment lead study author Anne Curtis (University at Buffalo, New York, USA) and team.

Patients in BLOCK HF (Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block) received a pacemaker or a implantable cardioverter-defibrillator (ICD) according to clinical indication, with 484 receiving the former device and 207 given the latter.

The average left ventricular ejection fractions were markedly different between the groups, at 42.9% in the pacemaker group and 33.0% in the ICD group. Nevertheless, both groups derived similar benefit from biventricular pacing, which the team says suggests that "the benefit of biventricular pacing is unlikely to be tightly linked to the ejection fraction."

Indeed, the relative reduction in the primary endpoint with biventricular versus right ventricular pacing was almost identical in the two groups, at 27% in the pacemaker group and 25% in the ICD group, as were the 95% confidence intervals.

"We conclude that the benefit of biventricular pacing in patients with atrioventricular block is similar with the two types of devices," say Curtis et al.

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