A study by a UC Irvine cardiologist suggests that cocaine users may be at increased risk of heart attacks because the drug directly weakens the heart muscle and causes it to skip beats.
In animal experiments conducted with large doses of cocaine, the drug caused heartbeats to weaken and the heart's process of contraction and relaxation to slow, said Dr. Charles Morcos, director of cardiovascular research at UC Irvine.
Morcos used pumps when inserting cocaine into the animals' hearts, rather than blood vessels, to rule out the previous theory that cocaine affects the heart only indirectly by causing blood vessel spasms that interrupt blood flow, he said.
"This is another way that cocaine affects the heart negatively," Morcos said.
Morcos said his findings do not contradict "the previous understanding of spasms (in blood vessels)" caused by cocaine. But he added that "it raises a lot of questions (such as) where in the mechanism of the heart does (cocaine) interfere?"
"It has quite a few implications," he said.
Morcos said preliminary results of his study were met with "strong interest" and "positive comments" when presented at the 37th annual scientific session of the American College of Cardiology, held in Atlanta. The results also were published, in abstract form, in the March, 1988, issue of the Journal of the American College of Cardiology, he said.
UCLA cardiologist Koonlawee Nademanee, who also attended and spoke at the Atlanta gathering, said that he is not completely familiar with Morcos' work but that the findings appear sound. Final judgment will come when the complete study is published, he said.
"It's quite interesting and has scientific merit," said Nademanee, an associate professor of medicine. "But we would like to see the whole paper published. Then you can see if there is any flaw or misinterpretation."
Morcos said he expects the findings to be published in their entirety within the next four months. He noted that the Journal of the American College of Cardiology, which published his preliminary results, accepts only 20% of all such submissions.
Although some of the concentrations of cocaine used in the studies on animals were extremely high, Morcos said, similar effects could occur in drug users who are small in size, are on medication or who may be drinking alcohol at the same time, or those highly sensitive to drugs in general.
Morcos said long-term use of cocaine can cause inflammation of the heart, which would deprive other organs of blood.