Implantable defibrillators save lives by shocking hearts back into a healthy rhythm, but that shock can cause physical and psychological trauma for the patient. Now, drugs used to help prevent abnormal heartbeats can reduce the need for these defibrillators to fire, according to a Canadian study.
"There can be a fair amount of psychological trauma from the shock, and it is actually fairly painful," notes Dr. Jeffrey J. Goldberger, director of cardiac electrophysiology at Northwestern University. He was not involved in the study, but has extensive experience with patients who have implanted defibrillators.
The international study, led by Dr. Stuart Connolly of McMaster University in Hamilton, Ontario, included 412 heart patients who received implantable defibrillators at 39 medical centers in the United States, Canada and Europe. Some of the patients were given beta blockers, the standard treatment. Others received beta blockers plus amiodarone, a drug that reduces arrhythmias, or abnormal heartbeats. (For more information about amiodarone, see page 192) And a third group received sotalol, another anti arrhythmia drug.
The risk of experiencing a shock during one year was 56% lower in the patients who got either the beta blocker-amiodarone combination or the sotalol treatment, compared with those who got a beta blocker alone. The beta blocker amiodarone combination was the most effective, reducing the incidence of shock by 73%.
However, some of the patients taking amiodarone reported side effects such as abnormally slow heartbeats and lung and thyroid problems, according to the researchers.
The researchers considered whether amiodarone or sotalol should be used immediately after defibrillator implantation or some time before the first shock occurs. Their answer, based on the study's findings, was that therapeutic decisions should be made on an individual basis.
In his practice, Goldberger says, "We typically individualize each patient, and we do not routinely put patients on amiodarone." He considers treatment with anti-arrhythmia drugs "when there is a high probability of a patienr having events, a lot of arrhythmias or if they already have had events." Approximately 40% of his defibrillator patients get one of these drugs, Goldberger says.
Dr. Robert L. Page, head of cardiology at the University of Washington, agrees that treatment needs to be tailored to each patient.
Drug therapy might be used immediately after implanting the defibrillator if there has been a high frequency of abnormal heartbeats or any anxiety or intolerance of the shock in the past, Page says.
For most patients, the decision on drug therapy will be made after implantation "if there is an indication that something further is needed,'' he says. Page estimates that more than 50% of his patients will be taking an anti-arrhythmia drug within two years after implantation, with most getting amiodarone because it is more effective. However, he might consider sotalol for some patients because it has a lower incidence of side effects.
"Ideally, it would be great if we could prevent all [shocks]," Goldberger says. 'A defibrillator is a wonderful thing; it saves lives. But the mechanism by which it saves lives is that first you must have a cardiac arrest, then the defibrillator resuscitates. A more ideal way would be to prevent the arrest from happening."