Pacing Both Ventricles Best for Heart Block Patients

For patients with atrioventricular (AV) block and depressed left ventricular ejection fraction (LVEF), biventricular pacing improves outcomes better than standard right ventricular pacing, according to a new study.

Researchers at the University of Buffalo (New York, NY, USA) enrolled 691 patients who had indications for pacing with AV block; New York Heart Association (NYHA) class I, II, or III heart failure; and a LVEF of 50% or less. The patients received a cardiac-resynchronization pacemaker or implantable cardioverter-defibrillator (ICD), and were randomly assigned to standard right ventricular pacing or biventricular pacing. The primary outcome was the time to death from any cause, an urgent care visit for heart failure that required intravenous therapy, or a 15% or more increase in the left ventricular end-systolic volume index.

The results showed that the primary outcome occurred in 190 of 342 patients (55.6%) in the right-ventricular-pacing group, as compared with 160 of 349 (45.8%) in the biventricular-pacing group, a significantly lower incidence rate. The results were similar in both the pacemaker and ICD groups. Left ventricular lead-related complications occurred in 6.4% of patients. The study was published in the April 25, 2013, issue of the New England Journal of Medicine (NEJM).

“The benefit was seen both in patients with cardiac resynchronization pacemakers and in those with implantable cardioverter-defibrillators,” concluded lead author Anne Curtis, MD, and colleagues. “The trial was limited by the large number of patients who switched from right ventricular pacing to biventricular pacing and by the high number of missing echocardiograms at various points during follow-up.”

Heart block occurs when the heart beats too slowly (bradycardia), since the electrical signals that tell the heart to contract are partially or totally blocked between the atria and the ventricles; thus the term atrioventricular block. Right ventricular pacing is used to restore an adequate heart rate in patients with AV block, but sometime induces left ventricular dysfunction and heart failure, presumably owing to the electrical and mechanical dyssynchrony that occurs with right ventricular pacing.

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