June 21, 1999 ANN ARBOR -- Researchers from the University of Michigan Health System's Division of Cardiology restored normal heart rhythms in 100 percent of study patients with atrial fibrillation through treatment with an ibutilide fumarate injection prior to an electrical shock to the heart. The successful findings appear today in the June 17 issue of the New England Journal of Medicine.
More than 2 million adults suffer with atrial fibrillation---rapid irregular heart contractions originating in the upper chambers of the heart. Atrial fibrillation can cause blood to pool, forming clots that could travel to the brain and result in a stroke. According to the American Heart Association, about 15 percent of strokes occur in people with atrial fibrillation. Stroke is the nation's third-leading cause of death and the No. 1 cause of adult disability, according to the National Stroke Association.
While atrial fibrillation is not usually life-threatening, it can lead to decreased cardiac output, congestive heart failure and low blood pressure.
"Since atrial fibrillation is the most common arrhythmia (irregular heart rhythm) observed in patients who visit a primary care setting, it is important to improve our understanding of the options available for treatment," says S. Adam Strickberger, M.D., associate professor in the Department of Internal Medicine and a study co-author. "The results of this study suggest that the use of ibutilide injection and cardioversion (electrical shock) represents an important new treatment option for patients suffering from atrial fibrillation."
Typically, doctors use electrical current alone to convert or "shock" the heart into a more normal rhythm. For this study, the investigators used a step-up protocol of electrical shock energy to determine the minimum energy required for successful cardioversion. In 20 percent of patients who were selected randomly to receive ibutilide pretreatment, electrical shock therapy was not needed at all. Therefore, the study suggests that giving a dose of ibutilide prior to an electrical shock may reduce the shock energy required, or in some cases eliminate the need for electrical cardioversion altogether.
Ibutilide fumarate is an injectable (class III) antiarrythmic medication that stabilizes electrical membranes by affecting sodium channels. Ibutilide has been used until now to convert patients from atrial fibillation to a normal heart rhythm without the electrical shock therapy, but it was not always successful..
In the study, 100 patients with atrial fibrillation lasting more than six hours, and up to more than 3 months were randomly assigned to pre-treatment with either ibutilide and electrical shock, or electrical shock alone. Conversion to normal heart rhythm occurred in all 50 patients who received ibutilide and in 36 of the 50 patients who received electrical shock alone. In the 14 patients in whom electrical shock alone failed, normal heart rhythm was restored when electrical shock was attempted again after the administration of ibutilide. Following injection, two of the patients developed an additional life-threatening arrhythmia (polymorphi ventricular tachycardia) that was quickly resolved with treatment.
"A 100 percent success rate in our study suggests a powerful beneficial drug effect; however, we would not expect a 100 percent success rate in wide spread clinical practice. For patients in whom electrical shock has failed, pretreatment with ibutilide may allow successful cardioversion of atrial fibrillation to a normal heart rhythm" said Gregory Michaud, M.D., co-author of the study.
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