Heart Procedure Reduces Need for Defibrillator Shocks
WEDNESDAY Dec. 26, 2007 -- A treatment that wipes out abnormal heart tissue reduces the number of shocks delivered to people who have defibrillators implanted after heart attacks, a new trial showed.
While those shocks do keep the heart going when it slips into abnormal rhythms, they are desirable to avoid not only because they are unpleasant to experience but carry hazards of their own, said study senior author Dr. Mark E. Josephson, chief of the cardiovascular division at Beth Israel Deaconess Medical Center in Boston.
"People with these devices have a lower quality of life because of the shocks and the fear of getting shocks," Josephson said. "With ablation, there was a marked reduction in any kind of therapy, and shocks specifically."
Ablation is a technique of identifying and eliminating cardiac tissue that can generate the kind of abnormal rhythm that sets the heart beating irregularly, so that a defibrillator shock is needed to restore normal heart rhythm.
The study led by Josephson included 128 people who had defibrillators implanted after heart attacks. Half of them underwent ablation, half did not. In an average follow-up period of 22.5 months, just eight of those who had ablation experienced defibrillator shocks, compared to 21 -- a full third -- of the group that did not have ablation.
And there was a marked reduction in deaths among those in the ablation group, Josephson said. Eleven of those who did not have ablation died, while there were just six deaths in the ablation group, he said. The numbers were too small to reach statistical significance, but Josephson described it as "a remarkable finding."
The study results are published in the Dec. 27 issue of the New England Journal of Medicine.
But the study did not address the issue of drug treatment to keep abnormal heart rhythm under control, said Dr. V.A. Mark Estes III, director of the cardiac arrhythmia center at Tufts New England Medical Center, and author of an accompanying editorial in the journal. None of the people in the trial were given anti-arrhythmia drugs, he said.
"Additional trials are needed to assess the comparative benefit of catheter ablation and anti-arrhythmic drugs, to identify which subgroups of patients are most likely to benefit, to evaluate the effect of operator expertise and to assess quality of life and cost," Estes wrote.
In addition, the trial "enrolled carefully selected patients and was conducted at highly experienced centers," Estes wrote. It's not clear whether the results would be as good at centers with less expertise, he said.
Drug treatment in such cases is problematical, Josephson said. "No data suggest that drugs would be effective," he said. "No drug has been shown to be particularly successful. Drugs also have side effects, and people must remember to take them. There needs to be some randomized trials showing that drugs reduce the need for defibrillator shocks."
Josephson said he was in full agreement with the need for expertise in applying ablation. "To identify potential sites and ablate them requires a skilled operator, electrophysiologists, training in mapping and in abrasion in particular," he said. "It all depends on the individual and the experience the individual has in this area. The procedure is intensive. We were fortunate in having a low incidence of any kind of side effect."
Given the right circumstances, benefits do flow to a person with an implanted defibrillator, Estes said. "These are really sick people who need these devices," he said. "But people don't like it even if they get an appropriate shock."
A guide to ablation is offered by the U.S. Food and Drug Administration.
Posted: December 2007
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