'Heart block' with pacemaker is safe treatment for atrial fibrillation

ROCHESTER, MINN. -- For patients who have not responded to medications, treating atrial fibrillation by permanently blocking a key portion of the heart’s electrical system and replacing it with a pacemaker leads to survival rates that are as good as those for patients receiving conventional drug therapy, according to a Mayo Clinic study published in this week’s New England Journal of Medicine.

As many as four million Americans have atrial fibrillation (AF), a group of electrical abnormalities that makes the upper chambers of the heart flutter at up to 500 cycles per minute. Some of these irregular impulses reach the ventricles, causing the heart to beat erratically and pump inefficiently. Symptoms of AF include rapid pulse, chest pain and lightheadedness. It is also an independent risk factor for stroke.

Medications can restore normal heart rhythms for some patients, but over half of those who are helped by medication will have a recurrence of AF within one year. A newer option, which is used only in patients who don’t respond to drug treatment, involves creating a "heart block" to keep atrial currents from reaching the ventricles. Radiofrequency energy is used to ablate, or burn, the atrioventricular (AV) node (the "junction box"), and patients then receive permanent pacemakers to keep the ventricles pumping at a desired rate.

"AV node ablation combined with permanent pacemaker implantation has previously been shown to help relieve symptoms of atrial fibrillation," says Win-Kuang Shen, M.D., a Mayo Clinic cardiologist and author of the study. "We have not known, however, whether creating a permanent heart block and making these patients pacemaker-dependent might negatively affect long-term survival."

The study compared mortality of 350 Mayo Clinic patients who received AV node ablation with a pacemaker between 1990 and 1998 to mortality of a group of similar AF patients on medication. The patients were followed for an average of three years, and mortality was also compared with the expected survival for an age- and sex-matched group from the Minnesota population. The pacemaker group did worse than the general population, but the results were equivalent to those for the medicated group. Among the pacemaker patients without significant heart disease, the survival was equivalent to the general population.

"This study provides the first evidence that ablation and pacing does not create additional risk of mortality," says Dr. Shen. "Ablation with pacing has improved the quality of life for many individuals whose atrial fibrillation did not respond to medication. Now patients and physicians can be reassured that this procedure is both safe and effective."

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