A government-mandated tracking system in France showed that over five years, physicians in that country treated 1,979 patients for serious health problems associated with the use of marijuana, and nearly 2 percent of those encounters were with patients who had cardiovascular problems, including heart attack, cardiac arrhythmia and stroke, and circulation problems in the arms and legs. In roughly one-quarter of those cases, the study found, the patient died.

In the United States, when young and otherwise healthy patients show up in emergency departments with symptoms of heart attack, stroke, cardiomyopathy and cardiac arrhythmia, physicians have frequently noted in case reports that these unusual patients are regular marijuana users.

Such reporting is hardly the basis for declaring marijuana use an outright cause of cardiovascular disease. But recently, cardiologists writing in the Journal of the American Heart Association warned that “clinical evidence … suggests the potential for serious cardiovascular risks associated with marijuana use.”

They called for data-collection efforts capable of detecting and measuring marijuana’s cardiovascular effect among U.S. users.

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“There is now compelling evidence on the growing risk of marijuana-associated adverse cardiovascular effects, especially in young people,” said Emilie Jouanjus, lead author of the French study, which was also published in the Journal of the American Heart Association. That evidence, Jouanjus added, should prompt cardiologists to consider marijuana use a potential cause of cardiovascular disease in patients they see.

In an editorial published April 23
in the American Heart Association journal, Drs. Sherief Rezkalla and Robert Kloner cited evidence that marijuana use probably increases clotting factors in the blood and that heavy use may lead to significant changes in the tiny vessels carrying blood to the heart and brain.