Len Bias' sudden cardiac arrest could have been caused by cocaine, by a heart ailment that his doctors missed or by a combination of the two, according to experts interviewed yesterday.

Cocaine can stop even a healthy heart by triggering a deadly disturbance of the heart rhythm or by raising the user's temperature, pulse and blood pressure so high that the heart fails. If a heart condition is present, the risks of the drug are magnified.

Police sources said yesterday evidence of cocaine was found in Bias' urine. Dr. John Smialek, chief medical examiner for the state of Maryland, said results of an autopsy will not be known for seven to 10 days.

Bias showed no sign of a heart ailment in yearly team physicals, including a special study to look for hidden heart disease, and no evidence of drug use in urine tests done during the past season, according to University of Maryland physicians.

He passed an examination for the Boston Celtics last month that included an electrocardiogram, a drug test, blood tests and X-rays, according to a Celtics source. In recent weeks, he passed physicals for other NBA teams and seemed to be "in perfect health," according to Maryland trainer Frank Grimaldi.

Yet, even these extensive screening tests could have failed to detect several potentially lethal heart conditions, according to Dr. Barry Maron, a senior investigator at the National Heart, Lung and Blood Institute.

Yesterday, Maron reviewed an electrocardiogram done on Bias as part of a University of Maryland study, and said, "It's not totally normal, really . . . " He said the tracing contained "some T-wave abnormalities," a finding that could signal a heart problem or could be insignificant.

"A lot of athletes have that," he said. "There's hardly any athlete that has a totally normal EKG."

Maron said Bias' electrocardiogram was interpreted as normal for the purposes of the study, conducted during the 1984-85 academic year to try to detect hidden heart disease in Maryland athletes. "We weren't providing a total workup for each one of those kids," he said. "We were trying to test whether it was possible to screen that many."

Maron said that when a young, healthy person dies of cardiac arrest, the most common explanation is a hidden heart defect, present from birth. In a study he conducted of 29 such deaths of athletes, the majority had hypertrophic cardiomyopathy, a disease of the heart muscle that causes thickening of the wall of the left ventricle. He said death occurs from an abnormal heart rhythm, usually during exercise.

Most victims of the disorder have a heart murmur or electrocardiogram pattern that alerts doctors, according to Dr. Sacared A. Bodison, coordinator of the Maryland's sports medicine program. She said Bias had none of these.

Another possible cause is Marfan's syndrome, an abnormality of connective tissue that causes weakness of the wall of the aorta, the huge artery that carries blood from the heart to the rest of the body. A 7-foot Maryland freshman, Chris Weisheit, was found to have the syndrome this year and was barred from basketball. Maron and Bodison said Bias had none of the physical characteristics, such as nearsightedness, loose joints or a breastbone deformity, that would suggest the Marfan's syndrome diagnosis.

But Maron said either condition could have gone undetected at Maryland, since Bias did not have an echocardiogram, a test that uses sound waves to create an image of the heart's chambers.

He said another potentially lethal condition in which a coronary artery supplying blood to the heart muscle is anatomically abnormal, usually can be detected only on an arteriogram, a test in which dye is injected into these arteries. Neither echocardiograms nor arteriograms are routinely done on athletes, he said.

As for cocaine, it can cause cardiac arrest even in a healthy heart. Cocaine is toxic to the heart and also stresses it by raising temperature, blood pressure and pulse rate, according to Greg Hayner, assistant professor of clinical pharmacy at the University of California at San Francisco.

He said the drug releases body stores of catecholamines, chemical transmitters that increase the metabolic rate and also sensitize the heart muscle to electrical stimulation, causing abnormal rhythms. Cocaine users can die from ventricular fibrillation, a chaotic disturbance of heart rhythm that prevents the organ from pumping blood to the body. He said the drug also can apparently cause spasm of the coronary arteries, especially in users of "free base" cocaine.

Bias became the third Maryland basketball player in 10 years to die of heart failure. Owen Brown, a forward who captained the 1974-75 Terrapins, and center Chris Patton each died within a 57-day period during the early part of 1976. The death of Brown, who was 22, was attributed to hypertrophic cardiomyopathy. That of Patton, who was 21, was attributed to Marfan's syndrome, which also killed U.S. volleyball star Flo Hyman earlier this year.

Dr. Richard Schwartz, the Alexandria cardiologist who treated Brown prior to his death, said yesterday, "My feeling is as it was then: these basketball and volleyball players are of a body type where there is an incidence of these abnormalities -- an enlarged septum in Brown's case and a weakened aorta in Patton's case -- and these things should be tested for."

In fact, those two deaths led Maryland to take a more aggressive approach in attempting to detect heart ailments. However, the university's new policy stops short of including electrocardiogram (EKG), stress tests or chest x-rays on a routine basis, due to costs. Bodison said such tests would be ordered if anything out of the ordinary was found in medical histories or physical exams. Following the deaths of Brown and Patton, university doctors had recommended the routine use of EKG and chest x-rays.

Bodison said Maryland athletes receive physicals each year, adding that many schools administer physicals to athletes only once every two years.

Staff writer Mark Asher contributed to this report.