Chronic methamphetamine use linked to cardiomyopathy.
"To our knowledge, this is the first study of its type to examine the relationship between chronic methamphetamine use and its effect on the heart," Melissa R. Robinson, M.D., reported in a poster at the annual scientific sessions of the American Heart Association.
"In contrast with cocaine, long-term methamphetamine use seems to have a direct, cardiotoxic effect, and promotes the development of severe, nonischemic, dilated cardiomyopathy," according to Dr. Robinson of the department of internal medicine at the University of California, Davis.
Although the number of chronic users of methamphetamine is not known, a 2001 survey estimated that more than 5 million people in the United States had tried the drug, the physician commented.
Dr. Robinson's review started with 226 patients who were either hospitalized at the UC Davis Medical Center or seen in the hospital's emergency department during 1993-2002 and reported using methamphetamine and were diagnosed with either cardiomyopathy or heart failure.
This list of patients was then pared to exclude those with another possible explanation for their heart disease, including a history of significant alcohol use (at least four drinks per day for at least 5 years), alcoholic cirrhosis, cocaine use, or severe coronary artery disease.
These exclusions left 53 patients who were methamphetamine users and had no clear etiology for their cardiomyopathy or heart failure. The average duration of drug use among these 53 patients was 5 years.
The patient's average age was 46 years, and 43% were younger than 45. Their average left-ventricular end-diastolic dimension was 66.3 mm, and 87% had an end-diastolic dimension of more than 55 mm, indicating severe dilated cardiomyopathy.
Echocardiography was done on 46 patients, who had an average left-ventricular ejection fraction of 25%; 35 of the 46 patients (76%) had an ejection fraction of less than 30%.
Several of the patients had severe complications while they were followed at UC Davis. Five patients had strokes, another five had recurrent ventricular arrhythmias that required implantation of a cardioverter defibrillator, and six had sudden deaths.
"These clinical findings were unusual given the relatively young age of these patients," Dr. Robinson commented.
Four patients had resolution of their cardiomyopathy after they stopped using methamphetamine.
Methamphetamine probably triggers cardiomyopathy by causing a chronic excess of catecholamines, similar to what happens in patients with a pheochromocytoma, an adrenal gland tumor, Dr. Robinson told this newspaper.
The effects of methamphetamine are exacerbated by its relatively long half-life, 8-12 hours.
In contrast, the half-life of cocaine is 30-60 minutes.
These findings show that chronic methamphetamine use can lead to severe cardiomyopathy, and physicians should think about these effects when caring for patients who use methamphetamine, she said.
BY MITCHEL L. ZOLER