Can We Learn New Tricks from an Old Drug in Treating Heart Attacks

An “old” drug has unique benefits for patients with acute myocardial infarction, a finding that may contribute to a new understanding of how heart attacks develop, according to an article in the July/August American Journal of Therapeutics.

In the definitive report, Dr. Marvin Bacaner of University of Minnesota describes the effects of the antiarrhythmic drug bretylium tosylate in preventing dangerous heart rhythm disorders and other complications after acute myocardial infarction (AMI; commonly known as “heart attack”).

Bretylium works by blocking release of the “fight or flight” hormone adrenaline, preventing activation of the sympathetic nervous system. Given intravenously, bretylium was once the mainstay of treatment for ventricular fibrillation and other heart rhythm disorders (arrhythmias) after AMI, although in recent years it has been largely replaced by other drugs.

However, Dr. Bacaner now believes that bretylium may offer unique advantages in heart attack treatment, and that it can be given effectively orally. In a study of 110 patients with AMI, potentially deadly arrhythmias developed in just eight percent of patients treated with bretylium, compared to 65 percent of those treated with a different drug, called lidocaine.

Bretylium’s adrenaline-blocking effect may lead to other benefits as well. In 31 percent of patients taking bretylium, the evolving heart attack did not develop into a “true” myocardial infarction, with permanent damage to the heart muscle. In contrast, 95 percent of patients treated with lidocaine developed a large heart attack.

A clue to the importance of blocking the sympathetic nervous system was that bretylium-treated patients remained warm and dry, with normal skin color. In contrast, patients receiving lidocaine were pale, sweaty, and cool, all signs of sympathetic nervous system activation.

Taken together, the findings suggest that the sympathetic nervous system plays an important role in the development of AMI. While blockage of coronary arteries by atherosclerosis is a major factor, Dr. Bacaner points out that it isn’t the only cause of the problem: some people have AMIs even though they have no coronary blockage, while others have blocked arteries but never experience a heart attack.

Sympathetic nervous system activation may be a previously underappreciated contributor to arrhythmias and heart muscle damage after heart attack. In the past, bretylium was available for intravenous use only. Dr. Bacaner has recently developed an oral form, which may offer a new approach to preventing arrhythmias as well as other dangerous complications.

“Dr. Bacaner is a true pioneer in the treatment of heart disease, and his development of an oral formulation of bretylium has the potential to extend the utility of discoveries made a half-century ago,” says AJT Editor Dr. John C. Somberg. “Although further, rigorous ’proof of concept’ studies will be needed, Dr. Bacaner’s ideas about the importance of the sympathetic nervous system may offer a new paradigm for the understanding of heart disease.”