Each year 80,000 - 100,000 people in the U.S die suddenly from heart attacks without ever having had any symptoms of heart disease. In some cases, the victims of these unheralded sudden cardiac deaths had been taking dietary supplements containing ephedrine.
In a new study in the Oct. 26, 2004 issue of the Journal of the American College of Cardiology, researchers show how ephedrine can cause sudden cardiac death in an animal model of asymptomatic heart disease.
"For our experiment, we went to the local health food store, bought ephedrine supplements and gave our animals the dose recommended on the label," said Philip B. Adamson, M.D., associate professor in the department of physiology and the department of medicine - cardiovascular diseases at the University of Oklahoma Health Sciences Center in Oklahoma City, Okla. and lead author of the study. "Ephedrine mimics the sympathetic nervous system, the part of the nervous system that makes the heart beat stronger and faster. In past experiments on obese, otherwise healthy individuals ephedrine did not raise their heart rates when they were either at rest or exercising." Dr. Adamson spoke at the American Medical Association's 23rd Annual Science Reporters Conference in Washington D.C.
"When we gave healthy animals ephedrine, we found exactly the same thing," Dr. Adamson said. "But the moment they developed a blockage in their heart artery, which we are able to cause reversibly, their heart rates went through the roof. It was the response to ischemia, a condition where there is a blockage of the heart's blood supply that was exaggerated by ephedrine."
"In ischemic heart disease, the blood supply to the heart becomes constricted, causing damage to the heart muscle and heart disease. However, sometimes the condition develops without any symptoms, leading to a sudden heart attack. Death can be the first symptom people with ischemic heart disease experience," Dr. Adamson said. "We wanted to determine how ephedrine, taken as directed, might cause someone with ischemic heart disease to have a potentially fatal heart attack."
"Ephedrine looks benign when you look at its effects on normal heart rates, but when there is a blockage, boom, ephedrine causes a potentially lethal arrhythmia," Dr. Adamson said. "The heart starts beating so fast, it can no longer pump blood."