By Michael H. Crawford, MD

Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco

Dr. Crawford reports no financial relationships relevant to this field of study.

SYNOPSIS: Among patients ≤ 50 years of age with first myocardial infarctions, use of cocaine or marijuana increased the likelihood of an ST-segment elevation myocardial infarction and the subsequent risk of all-cause and cardiovascular mortality.

SOURCES: DeFilippis EM, Singh A, Divakaran S, et al. Cocaine and marijuana use among young adults with myocardial infection. J Am Coll Cardiol 2018;71:2540-2551.

Lee JD, Schatz D, Hochman J. Cannabis and heart disease: Forward into the great unknown? J Am Coll Cardiol 2018;71:2552-2554.

As more states legalize recreational marijuana, its use is on the rise, yet we know little about its health effects. Cocaine is well recognized as a risk factor for myocardial infarction (MI).

DeFilippis et al studied the prevalence of substance abuse among patients ≤ 50 years of age with their first MI and its relation to outcomes. Investigators used chart review or toxicology screen on MI admission to determine if patients used cocaine or marijuana prior to MI. Patients who used both substances were put in the cocaine group for subanalyses. Opioid use was discovered but was not analyzed because there were insufficient data to distinguish prescription use from nonprescription use. Methamphetamine and other substances also were detected but constituted too few cases for analysis. The primary outcomes of interest were all-cause and cardiovascular mortality.

Among 2,097 young MI patients, 11% used cocaine or marijuana, one-third of whom used both substances. ST-segment elevation myocardial infarctions (STEMIs) were more common in the substance abuse patients (65% vs. 52%; P < 0.001). Diabetes and hyperlipidemia were less common in substance abuse patients (15% vs. 20%; P = 0.05; and 46% vs. 61%; P < 0.001, respectively). Tobacco use was more common in substance abuse patients (70% vs. 49%; P < 0.001). Substance abuse was associated with a higher cardiovascular mortality (hazard ratio [HR], 2.22; 95% confidence interval [CI], 1.27-3.70; P = 0.005) and all-cause mortality (HR, 1.99; 95% CI, 1.35-2.97; P = 0.001) after adjustment for baseline covariates over a mean follow-up of 11 years.

The authors concluded these findings support the current guidelines, which recommend screening young adults with their first MI for substance use and counseling users about the importance of abstinence to prevent future events.

COMMENTARY

This analysis exhibits that despite a generally lower incidence of traditional risk factors, substance users had a higher incidence of STEMIs than nonusers. This generates the hypothesis that substance abuse is a risk factor for early MI. Also, MIs in the substance abuse group were more likely to be discovered because of out-of-hospital cardiac arrest, which was driven by the marijuana users. Cocaine has been recognized as a trigger for acute MI, probably because cocaine use increases heart rate, blood pressure, and coronary vasoconstriction. However, we know comparatively little about the effects of marijuana. Marijuana can be similar to tobacco smoking in that one inhales burning vegetable matter in both instances. Still, other effects probably could be attributed to chemicals in marijuana, which would be more relevant to vaporized cannabis oil and edibles. There is evidence that tetrahydrocannabinol increases plasma catecholamines, impairs vascular endothelial function, and decreases myocardial contractility. Thus, marijuana may not be the benign recreational drug that it is touted to be.

The major limitation to the DeFilippis et al study was the potential effects of multiple confounders. The investigators adjusted the HR calculations for other known risk factors and showed about a two-fold increase in all-cause and cardiovascular mortality. However, cocaine and marijuana users also could smoke tobacco, drink alcohol, or take opioids. Also, substance users may be more likely to participate in other risky behaviors and have a higher prevalence of hepatitis C, HIV, and depression. These factors could affect mortality post-MI and were not assessed in this study. Also, the prevalence of substance abuse in the risk population (age < 50 years) could not be ascertained. Thus, the relative risk of substance abuse causing an MI is unknown.

What is clear is that substance abuse patients are at higher risk for adverse events post-MI. When one encounters a patient with an MI who uses substances, it would be reasonable to counsel him or her that quitting would be in their best interest.