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BIVENTRICULAR PACING: RANDOMIZED RESULTS ARE IN

About one third of patients with chronic heart failure have intraventricular conduction delays, which result in dyssynchronous, inefficient cardiac contraction. In several nonrandomized clinical trials, resynchronization via simultaneous pacing of the right and left ventricles has improved cardiac function and quality of life. In this industry-supported, multicenter trial, 453 patients with NYHA class III or IV heart failure, ejection fractions of <35%, and QRS durations of 130 msec each received a cardiac-resynchronization device and, then, were randomized to biventricular pacing or to no pacing for 6 months. Standard heart-failure therapy was maintained. Initially, 571 patients were enrolled, but implantation was unsuccessful in 43 patients, 2 required continuous pacing, 2 died, and data on 71 were used for a 3-month pilot phase.

Compared with controls, patients in the biventricular-pacing group fared significantly better on the three 6-month primary endpoints -- 6-minute walk distance (median change, +39 vs. +10 m), improvement in NYHA class, and quality-of-life improvement -- and on stress-test exercise duration (median change, +81 vs. +19 sec), ejection fraction (median change, +4.6% vs. -0.2%), rate of hospitalization for worsening heart failure (8% vs. 15%), and need for intravenous heart-failure medication (7% vs. 15%). The between-groups mortality difference was nonsignificant (12 deaths in the biventricular group and 16 in the control group).

Comment: For the first time, a prospective, randomized trial has shown that biventricular pacing improves heart-failure symptoms. It is striking that these benefits were achieved even with optimal medical management of heart failure. On the basis of these findings, physicians should consider referrals for biventricular pacing in patients with drug-refractory class III or IV heart failure and notable intraventricular conduction delay. However, enthusiasm must be tempered by the high rate of unsuccessful implantation (up to 10%) and by the procedure's length and potential for complications. Further research must assess which patient subgroups are most likely to benefit from biventricular pacing and from biventricular implantable defibrillators (vs. less expensive pacemakers).

— Hugh Calkins, MD

Published in Journal Watch Cardiology January 1, 2003

Citation(s):

Abraham WT et al. for the MIRACLE Study Group. Cardiac resynchronization in chronic heart failure. N Engl J Med 2002 Jun 13; 346:1845-53.

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• Medline abstract (Free)

Hare JM. Cardiac-resynchronization therapy for heart failure. N Engl J Med 2002 Jun 13; 346:1902-5.

• Original article (Subscription may be required)
• Medline abstract (Free)