Ventricular Pacing Saves More Lives than Dual-Chamber Pacing

In a surprising result, a study has shown that implantable cardioverter defibrillators (ICDs) with simple ventricular backup pacemaker therapy provide better outcomes than those with sophisticated dual pacing of the right atrial and ventricular chambers. The study was published in the December 25, 2002, issue of The Journal of the American Medical Association.

ICD therapy is usually given to patients with significant previous damage to the heart muscle, whose most common cause of death is congestive heart failure (CHF). Previous evaluations of ICD therapy showed that devices with a simple pacemaker that stimulated the heart only when the rate dropped very low saved lives when compared to the best medications. However, newer ICDs include a pacemaker designed to maintain an optimal heart rate that is automatically adjusted according to the level of the patient's activities.

The current study involved 506 patients with indications for ICD therapy. All had dual-
chamber pacemaker ICDs implanted and were then randomized to a pacing mode of ventricular backup pacing or dual-chamber rate-responsive pacing. All were given angiotensin-converting enzyme (ACE) inhibitors and beta blockers. The study was terminated ahead of schedule because of the significant trend toward worse outcome in the group receiving dual-chamber pacing. Specifically, one-year survival without death or hospitalization in the back-up pacing group was 83.9%, versus 73.3% in the group with dual-chamber pacing.

The researchers noted that when the ICD pacemaker function is activated in the right side of the heart, it may disturb the synchronization with the left side and cause the patient's heart to become less efficient and perhaps to deteriorate. They also noted, however, that there are patients who have ailments that result in dangerously slow heartbeats who can benefit from dual-chamber pacing but that other patients, who do not need the pacemaking function, should probably avoid using the dual-chamber pacing device.

"The DAVID (dual chamber and VVI implantable defibrillator) study produced opposite results from expectations,” said Bruce L Wilkoff, M.D., director of cardiac pacing and tachyarrhythmia devices at The Cleveland Clinic (OH, USA) and chairman of the study's steering committee. The ICDs used in the study were supplied by St. Jude Medical, Inc. (St. Paul, MN, USA).




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