McMaster University

McMaster University

Faculty of
Health Sciences

Minimizing shocks in patients with installed defibrillators

Published: January 11, 2006
Family Medicine Photo
If you have an abnormal heart rhythm, an implanted defibrillator can save your life, but the high voltage jolts can hurt.

McMaster University researchers have found that using a combination of drugs can help stop the painful shocks for these patients.

In a study published today in the Journal of the American Medical Association (JAMA), principal investigator Dr. Stuart J. Connolly and his team report that using the antiarrhythmic drug amiodarone, in combination with the standard beta-blocker therapy, is effective in preventing both appropriate and inappropriate shocks that can occur in patients with implantable cardioverter defibrillators (ICDs).

Dr. Stuart J. Connolly, a professor of medicine for the Michael G. DeGroote School of Medicine was the principal investigator for the study. He and his colleagues compared amiodarone plus a beta-blocker, with the antiarrhythmic drug sotalol alone, and with the standard beta-blocker therapy alone.

The randomized, controlled clinical trial, evaluated 412 patients at 39 clinical centers in the United States, Canada and Europe. Patients received a dual-chamber ICD within 21 days before randomization. Antiarrhythmic drug therapy began immediately after implant.

The study showed that 10 per cent of patients with an ICD received shocks when taking the antiarrhythmic drug amiodarone combined with a beta blocker, compared to 24 percent of patients on the antiarrhythmic drug sotalol, and 38 percent of patients on a beta blocker alone.

Amiodarone combined with a beta blocker reduced the occurrence of shocks by suppressing ventricular tachycardia, sinus tachycardia and supraventricular arrhythmias. The chance of a patient having an inappropriate shock was reduced to only 3.3 percent per year.

"What this study makes clear is that, despite the ability of ICDs with advanced dual-chamber discrimination algorithms to reduce the occurrence of inappropriate therapies, the use of antiarrhythmic drugs can significantly reduce ICD shocks," said Dr. Connolly. "Among this category of drugs, amiodarone is considerably more effective against shocks than sotalol."

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