Toker’s Paradox? Marijuana Users Face Lower Short-Term Risks After Acute MI, Study Hints

CHICAGO, IL—Marijuana use is associated with lower short-term risks of death and shock among patients admitted for acute MI, although the need for mechanical ventilation is greater in pot users, an analysis of administrative claims shows.

The reasons are unclear, presenter Cecelia Johnson-Sasso (University of Colorado Denver, Anschutz Medical Campus, Aurora, CO), told TCTMD during a poster session at the American College of Cardiology 2016 Scientific Sessions last week. Marijuana might provide benefits through direct effects on the endocannabinoid system, she said, but it could also be that disease was less severe in patients with reported marijuana use.

More research on the health effects of the drug is needed before any definitive conclusions can be made, she said.

“We don’t really know what it does. It’s our responsibility as clinicians and scientists to figure out what it does, so we can protect the population from possible adverse effects or know how to treat [patients] appropriately if they come in on this substance,” said Johnson-Sasso, who will be entering her third year of medical school soon.

Meeting co-chair Jeffrey Kuvin, MD (Tufts Medical Center, Boston, MA), who commented on the study for TCTMD, agreed, saying that “we as clinicians and cardiologists need to understand the effects of marijuana better on the cardiovascular system.”

He said the study is interesting but because of numerous limitations—including the lack of detailed clinical information, long-term follow-up, or information on how patients used marijuana (ie, smoked or ingested)—further research is warranted.

The issue has taken on greater importance in recent years as more widespread legalization has led to increasing use of marijuana. That has been accompanied by growing interest in potential health effects. Little is known, however, about the possible impact on cardiovascular health.

In the current study, the researchers looked at administrative hospital records from eight states—California, New York, New Jersey, Vermont, New Hampshire, Colorado, Texas, and West Virginia—for adults for acute MI between 1994 and 2013. After exclusion of patients 70 years and older because they were much less likely to use marijuana than younger patients as well as users of cocaine, methamphetamine, or alcohol, there were 3,854 marijuana users (either self-reported or confirmed through testing) and 1,270,043 controls left for the analysis.

That large disparity in patient numbers seems to be an indication that marijuana use was drastically underreported, Johnson-Sasso said.

On multivariate adjustment, there was no difference between the groups in the rate of the primary composite outcome (death, mechanical ventilation, cardiac arrest, intra-aortic balloon pump [IABP] placement, or shock in the hospital). But marijuana users were less likely to die (OR 0.83; 95% CI 0.68-1.00), have shock (OR 0.74; 95% CI 0.62-0.89), or have an IABP placed (OR 0.80; 95% CI 0.66-0.98) and more likely to require mechanical ventilation (OR 1.19; 95% CI 1.06-1.34).

They were also less likely to undergo PCI (OR 0.72; 95% CI 0.66-0.78) despite similar rates of coronary angiography. The researchers did not have access to angiograms to evaluate whether that is an indication of less severe events in the marijuana group, Johnson-Sasso said.

Potential Mechanisms Unclear

The study was not designed to establish causal relationships, but there is biological plausibility to the association between marijuana use and better outcomes. Johnson-Sasso pointed to two components of the endocannabinoid system, CB1 and CB2 receptors, which are found throughout the body and appear to be responsible for immunosuppressive and anti-inflammatory effects of marijuana. There is evidence from mouse studies that giving a CB2 agonist during reperfusion reduces infarct size after MI, she noted.

Her research group will be exploring that possibility in future studies and also looking into whether marijuana might be causing adverse cardiac events, she said.

Kuvin would not speculate on potential mechanisms but said the study “brings to mind what’s called the smoker’s paradox in that, in some cases, smokers seem to do a little bit better with acute myocardial infarction. Whether this is the same mechanism or whether this is totally different, I just don’t know because I don’t think we know the mechanism.”

But more research could be fruitful, he suggested. “I think from a pharmacologic standpoint we know that marijuana does have uses in medicine and there may be something good that comes out of this,” he said.

• Johnson-Sasso CP, Kao DP, Walker LA. Marijuana use and short-term outcomes in patients hospitalized for acute myocardial infarction. Presented at: American College Cardiology 2016 Scientific Sessions. April 3, 2016. Chicago, IL.

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