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Don't Rush to Implant a Dual-Chamber ICD

This study challenges the assumed superiority of dual-chamber pacing in patients with implanted cardioverter-defibrillators.

Studies showing that implantable cardioverter-defibrillators (ICDs) effectively prevent sudden cardiac death in high-risk patients have been conducted mostly on single-chamber ICDs programmed to provide backup ventricular pacing, typically at 40 bpm (VVI-40). Cardiologists have assumed that ICDs with dual-chamber pacing benefit patients by allowing optimization of pharmacologic therapy for heart failure, by limiting supraventricular arrhythmias, and by optimizing resting and exercise heart rates. This manufacturer-supported, single-blind study challenges that assumption.

Dual-chamber ICDs with backup VVI-pacing capacity were implanted in 506 patients (mean age, 65) who had standard indications for ICD therapy and did not have indications for antibradycardia pacing. Then, patients were randomized to backup VVI-40 pacing alone or to dual-chamber responsive pacing at 70 bpm (DDDR-70). All patients received maximally tolerated standard heart-failure drug therapy.

Percentages of ventricular-paced beats were about 60% in the DDDR-70 group and roughly 2% in the VVI-40 group. After a median follow-up of 8.4 months, the study was terminated because of a higher combined rate of death or heart-failure hospitalization in the DDDR-70 group than in the VVI-40 group (26.7% vs. 16.1%, P0.03). Death rates were 10.1% and 6.5%, respectively; heart-failure hospitalization rates were 22.6% and 13.3%.

Comment: These data clearly challenge the conventional wisdom that dual-chamber pacing is superior to backup VVI pacing alone in patients with ICDs by documenting worse outcome with dual-chamber pacing. The findings, though striking, are consistent with recent studies that highlight the importance of simultaneous contraction of the right and left ventricles; right-ventricular pacing may create discoordinate cardiac contraction. Further studies must determine whether atrial-based pacing alone (with a long AV interval to allow native conduction to the ventricles) is superior to backup VVI pacing and whether biventricular pacing can eliminate the apparent adverse consequences of RV pacing alone. For now, clinicians should rely on single-chamber ICDs or dual-chamber ICDs that are programmed to provide backup VVI pacing alone.

— Hugh Calkins, MD

Published in Journal Watch Cardiology February 21, 2003

Citation(s):

The DAVID Trial Investigators. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA 2002 Dec 25; 288:3115-23.

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

Kass DA. Pathophysiology of physiologic cardiac pacing: Advantages of leaving well enough alone. JAMA 2002 Dec 25; 288:3159-61.

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