Researchers are beginning to find evidence that cocaine use can cause heart attacks, irregular heartbeats and sudden death in young patients not normally at risk of heart disease.

Three separate studies by researchers at Tufts University School of Medicine in Boston, Stanford University in Palo Alto, Calif., and Brookdale Hospital in Brooklyn have linked cocaine use to cardiac complications.

Cocaine has been implicated in the cardiac arrest and sudden death last week of University of Maryland basketball star Len Bias.

The Tufts group studied seven patients -- six men and one woman -- who admitted to having used cocaine before entering the hospital for treatment of irregular heartbeats. Six used cocaine regularly.

"Two of the male patients died suddenly of heart-related problems," said Dr. Jeffrey M. Isner, associate professor of medicine at Tufts. "In one, an autopsy showed evidence of a heart attack and a blood clot in a coronary artery that was narrowed by artherosclerosis. The other died presumably of cardiac arrhythmia irregular heartbeats ."

Last year, doctors at Brookdale Hospital investigated six cases of cardiac problems in cocaine users ranging in age from 27 to 44 and found that they suffered spasms of the coronary arteries.

"The patients had normal, healthy arteries but, nonetheless, suffered spasms of the coronary arteries," said Dr. Alan F. Lyon, Brookdale's director of medicine.

At Stanford University, pathologist Dr. Henry Tazelaar recently completed a study of 30 autopsies of young cocaine users performed by the San Francisco coroner's office.

"The average age of the deceased was 32. We found lesions on muscle cells of the heart of cocaine users that are like those seen when there's an increase in adrenalin. Cocaine was found in urine and blood samples. The control group didn't have such lesions," said Tazelaar, whose findings have been submitted to The New England Journal of Medicine.

The details of how cocaine affects the cardiovascular system have yet to be worked out.

"We do know cocaine acts similar to speed or dexedrine, increasing heart rate and blood pressure," said Tufts' Isner. "It doesn't clog arteries. We speculate that this precipitates the release of large amounts of adrenelin. The heart is asked to do more work at a faster rate than it can do. The heart doesn't get enough blood to function properly, despite the arteries being open. This can cause an unstable electrical situation within the heart muscle."

"Cocaine's effect on the heart has been underestimated," said Isner. Although no hard data on the connection exists, during the past few years, emergency room doctors and specialists have been seeing an increase in heart attacks, ventricular arrhythmias (irregular heartbeats) and sudden death in patients younger than age 30.

"The physicians' observations have been shared informally at medical meetings. At the same time, we know cocaine use has increased. When young patients who are not at risk have heart attacks, arrhythmias, or die suddenly, we want to know why. The relationship between cocaine use or abuse and the heart is worth pursuing," said Isner, who presented his research at the American Heart Association meeting last year.

"Often the death of patients following excessive cocaine use is attributed to central nervous system or respiratory depression, because signs of cardiac disorder are not specifically searched out," Isner said.

Isner concedes that the evidence implicating cocaine in the deaths he studied is circumstantial. He points out, however, that the patient who had artherosclerosis had not had clinical symptoms of the heart trouble until after using cocaine.

"A heart attack may have occurred anytime. It did after using cocaine. It's like the heart attack that happens after shoveling snow," Isner said. "There's an assumed relationship between the shoveling and the attack."

Isner and his colleagues found most of the cardiac problems observed in the cocaine users were related to irregular heartbeats. They also believe cocaine can cause coronary arteries to spasm, which cuts to the blood flow to the muscular cells of the heart.

Three patients, despite experiencing ventricular arrhythmias, had normal angiograms -- diagnostic X-ray images showing that the blood vessels of their hearts looked healthy, said Isner.

Doctors know that snorting cocaine can cause blood vessels in the nose to constrict and can kill nasal tissue, Isner said. He speculated that cocaine could have the same effect on the heart's blood vessels.

"Up to now, even many doctors have considered cocaine relatively harmless -- just as they did with marijuana -- particularly when compared to heroin. Doctors may ask if a patient smokes cigarettes, but few ask about use of cocaine or other drugs," Isner said. "But now they should."

Laura White is a free-lance writer living in Boston.