Triggering myocardial infarction by marijuana

Background-Marijuana use in the age group prone to coronary artery disease is higher than it was in the past. Smoking marijuana is known to have hemod ynamic consequences, including a dose-dependent increase in heart rate, sup ine hypertension, and postural hypotension; however, whether it can trigger the onset of myocardial infarction is unknown. Methods and Results - In the Determinants of Myocardial Infarction Onset St udy, we interviewed 3882 patients (1258 women) with acute myocardial infarc tion an average of 4 days after infarction onset. We used the case-crossove r study design to compare the reported use of marijuana in the hour precedi ng symptoms of myocardial infarction onset to its expected frequency using self-matched control data. Of the 3882 patients, 124 (3.2%) reported smokin g marijuana in the prior year, 37 within 24 hours and 9 within 1 hour of my ocardial infarction symptoms. Compared with nonusers, marijuana users were more likely to be men (94% versus 67%, P <0.001), current cigarette smokers (68% versus 32%, P <0.001), and obese (43% versus 32%, P=0.008). They were less likely to have a history of angina (12% versus 25%, P <0.001) or hype rtension (30% versus 44%, P=0.002). The risk of myocardial infarction onset was elevated 4.8 times over baseline (95% confidence interval, 2.4 to 9.5) in the 60 minutes after marijuana use. The elevated risk rapidly decreased thereafter. Conclusions - Smoking marijuana is a rare trigger of acute myocardial infar ction, Understanding the mechanism through which marijuana causes infarctio n may provide insight into the triggering of myocardial infarction by this and other, more common stressors.