Biventricular Pacing Found Superior to Right Ventricular Pacing

Researchers at the Chinese University of Hong Kong (China), the Malaysian National Heart Institute (Kuala Lumpur), and other institutions participating in the prospective, double-blind, multicenter Pacing to Avoid Cardiac Enlargement (PACE) trial, randomly assigned 177 patients in whom a biventricular pacemaker had been successfully implanted to receive either biventricular pacing (89 patients) or right ventricular apical pacing (88 patients). The primary endpoints were the left ventricular ejection fraction (LVEF) and left ventricular end-systolic volume at 12 months.

The results showed that at 12 months, the mean LVEF was significantly lower in the right-ventricular-pacing group than in the biventricular-pacing, with an absolute difference of 7.4%, whereas the left ventricular end-systolic volume was significantly higher in the right-ventricular-pacing group than in the biventricular-pacing group, with a relative difference between the groups in the change from baseline of 25%. The harmful effect of right ventricular apical pacing occurred in prespecified subgroups, including patients both with and without preexisting left ventricular diastolic dysfunction. Eight patients in the right-ventricular-pacing group (9%) and one in the biventricular-pacing group (1%) had ejection fractions of less than 45%; there was one death in the right-ventricular-pacing group, and six patients in the right-ventricular-pacing group; five in the biventricular-pacing group were hospitalized for heart failure. The study was published in the November 15, 2009, issue of the New England Journal of Medicine (NEJM).

"These early results show biventricular pacing may be superior to pacing only in the right ventricle to preserve the heart's normal left ventricle size and pumping ability for these pacemaker patients,” said lead author Cheuk-Man Yu, M.D., of the Chinese University of Hong Kong. "As the first randomized study with this patient population, these initial results suggested that ensuring synchrony of the ventricles can help maintain patient health.”

A cardiac resynchronization therapy-pacemaker (CRT-P) is implanted in the upper chest to resynchronize (without defibrillation) the contractions of the ventricles by sending small electrical pacing impulses to the heart muscle, thus helping the heart pump blood throughout the body more efficiently. CRT is intended to complement standard drug treatment, and dietary and lifestyle modifications. The PACE study involves 177 patients at four hospitals in Asia who had a Medtronic (Minneapolis, MN, USA) Insync III CRT-P implanted, with no prior history of heart failure, normal left ventricle function, and an ejection fraction greater than or equal to 45%.

Related Links:
Chinese University of Hong Kong
Malaysian National Heart Institute
Medtronic