His team reported, “Although marijuana is smoked with fewer puffs, larger puff volumes and longer breath holds may yield greater delivery of inhaled elements.” In other words, when compared to tobacco smoking, exposure to chemicals damaging to the heart and lungs may be even greater from smoking marijuana.
Dr. Vaduganathan said he was especially concerned about the increasing number of heart attacks among marijuana users younger than 50. In a registry of cases created by his colleagues, in young patients suffering a first heart attack, “marijuana smoking was identified as one factor that was more common among them.” The registry revealed that, even when tobacco use was taken into account, marijuana use was associated with twice the hazard of death among those under age 50 who suffered their first heart attack.
Other medical reports have suggested possible reasons. A research team headed by Dr. Carl J. Lavie of the John Ochsner Heart and Vascular Institute in New Orleans, writing in the journal Missouri Medicine, cited case reports of inflammation and clots in the arteries and spasms of the coronary arteries in young adults who smoke marijuana.
Another damaging effect that has been linked to marijuana is disruption of the heart’s electrical system, causing abnormal heart rhythms like atrial fibrillation that can result in a stroke. In one survey of marijuana smokers, the risk of stroke was increased more than threefold.
These various findings suggest that a person need not have underlying coronary artery disease to experience cardiovascular dysfunction resulting from the use of marijuana. There are receptors for cannabinoids, the active ingredients in marijuana, on heart muscle cells and blood platelets that are involved in precipitating heart attacks.
Cannabinoids can also interfere with the beneficial effects of various cardiovascular medications, including statins, warfarin, antiarrhythmia drugs, beta-blockers and calcium-channel blockers, the Boston team noted.
The researchers found that in an analysis of 36 studies among people who suffered heart attacks, the top three triggers were use of cocaine, eating a heavy meal and smoking marijuana. And 28 of 33 systematically analyzed studies linked marijuana use to an increased risk of what are called acute coronary syndromes — a reduction of blood flow to the heart that can cause crushing chest pain, shortness of breath or a heart attack.