Marijuana Use Tied to Repeat MI, Stroke After PCI

Marlene Busko

November 19, 2020

Marijuana use was associated with a higher prevalence of recurrent myocardial infarction (MI) and a greater risk of bleeding or stroke after percutaneous coronary intervention (PCI) in separate studies.

Rhushik Bhuva, MD, presented the recurrent-MI results from a national US study, and Sang Gune K. Yoo, MD, presented the PCI study, which used data from a Michigan cohort. The studies were presented at the virtual American Heart Association (AHA) Scientific Sessions 2020.

Both studies "add to our accumulating knowledge of the cardiovascular risks of marijuana," Ersilia M. DeFilippis, MD, a cardiology fellow at Columbia University Irvine Medical Center, New York City, who was not involved with this research, told theheart.org | Medscape Cardiology.

DeFilippis and the two study authors say clinicians and patients need to be more aware of cardiovascular risks from smoking marijuana, and they call for more patient screening, counseling, and research.

Need for Screening, Counseling

Marijuana is a Schedule 1 controlled substance in the United States, which makes it illegal to conduct rigorous controlled trials of marijuana products. Existing knowledge is therefore based on observational studies, DeFilippis noted.

She was lead author of a review of marijuana use by patients with cardiovascular disease. The review was published in January 2020 in the Journal of the American College of Cardiology. An AHA scientific statement about marijuana and cardiovascular health was published in Circulation in August 2020.

Both documents drew attention to risks from marijuana use in patients with cardiovascular disease.

Until more data are available, "I think it's absolutely critical" that cardiologists and general providers screen patients for marijuana use, "either at the time of their MI or ideally prior to that, when they are making a cardiovascular risk assessment," said DeFilippis.

That is also the time to "counsel patients, especially those who have had an MI, about risks associated with continuing to use marijuana."

Importantly, providers and patients need to be aware that "cannabinoids, through the cytochrome P450 system, can interact with well-known cardiovascular medications, which we know provide benefit in the post-MI period," she added. "For example, marijuana can interfere with beta blockers, statins, antiarrhythmics, and certain anticoagulants."

Bhuva, a cardiology fellow with the Wright Center for Community Health, Scranton, Pennsylvania, said that it is "concerning" that "recurrent heart attacks and cardiac interventions [were] higher among cannabis users, even though they were younger and had fewer risk factors for heart disease.

"Spreading awareness regarding the potential risk of recurrent heart attacks in middle-aged, African American and male cannabis users and screening them at an earlier age for potential risk factors of future heart attacks should be encouraged among clinicians," he urged in a statement from the AHA.

Yoo, an internal medicine resident at the University of Michigan, Ann Arbor, pointed out that in their study of patients who underwent PCI after MI or because they had coronary artery disease, those who smoked or vaped marijuana were younger and were more likely to be male. They were less likely to have traditional cardiovascular risk factors except for smoking tobacco, which was highly prevalent.

After propensity matching, patients who used marijuana had a 1.5-fold increased risk of in-hospital bleeding and an 11-fold higher risk for in-hospital stroke following PCI.

However, the absolute number of strokes in PCI was small, and the confidence interval was wide (indicating a large uncertainty), Yoo pointed out to theheart.org | Medscape Cardiology.

These risks "should not deter patients from undergoing these [lifesaving] procedures," he said; however, clinicians should be aware of these risks with marijuana use and should screen and counsel patients about this.

Hospitalized Patients With Prior MI

Bhuva and colleagues identified patients from the National Inpatient Sample who were hospitalized in the United States from 2007 to 2014 and who had had a prior MI and had undergone revascularization with PCI or coronary artery bypass grafting (CABG).

There were about 8 million hospital stays per year. The database did not specify the type of marijuana that patients used.

During the 8-year study period, many states legalized or decriminalized medical and/or recreational marijuana, and marijuana use increased steadily, from 0.2% to 0.7%.

Compared to nonusers, those who used marijuana were younger (median age, 53 years vs 72 years), and there were more men (77% vs 62%) or Black persons (34% vs 10%; all P < .001).

Fewer marijuana users had hypertension (72% vs 75%), diabetes (24% vs 33%), or dyslipidemia (51% vs 58%; all P < .001).

More marijuana users underwent a repeat MI (67% vs 41%).

On the other hand, marijuana users, who were younger and healthier than the other patients, were less likely to die during hospitalization for a recurrent MI (0.8% vs 2.5%), and their hospital costs were lower.

The researchers acknowledge that study limitations include lack of information about marijuana type (smoked, edible, medicinal, or recreational) or dose, as well as the time from marijuana use to cardiac event.

In-Hospital Outcomes After PCI

Yoo and colleagues analyzed data from patients who underwent PCI from January 1, 2013, to October 1, 2016, at Michigan's 48 nonfederal hospitals, which are part of the Blue Cross Blue Shield Michigan Cardiovascular Consortium PCI registry.

In this cohort, 3970 patients (3.5%) had smoked or vaped marijuana in the month prior to PCI, and 109,507 patients had not done so.

The marijuana users were younger (mean age, 54 vs 66) and were more likely to be male (79% vs 67%) and to smoke cigarettes (73% vs 27%).

They were less likely to have hypertension, type 2 diabetes, dyslipidemia, cerebrovascular disease, or prior CABG and were equally likely to have had a prior MI (36%).

Compared to nonusers, marijuana users were more likely to present with NSTEMI (30% vs 23%) or STEMI (27% vs 16%) and were less likely to present with angina.

Using propensity score matching, the researchers matched 3803 marijuana users with the same number of nonusers.

In the matched cohort, patients who used marijuana had a greater risk of in-hospital bleeding (adjusted odds ratio [aOR], 1.54; 95% CI, 1.20 – 1.97; P < .001) or stroke (aOR, 11.01; 95% CI, 1.32 – 91.67; P = .026) following PCI.

Marijuana users had a lower risk for acute kidney injury (2.2% vs 2.9%; P = .007). Transfusion and mortality rates were similar in both groups.

The researchers acknowledge study limitations, including the fact that it did not include marijuana edibles, that the results may not be generalizable, and that marijuana use is now likely more common in Michigan following legalization of recreational marijuana in 2018.

Bhuva, Yoo, and DeFilippis have disclosed no relevant financial relationships.

American Heart Association (AHA) Scientific Sessions 2020: Abstracts P380 and P1916.

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