Research Highlights:

  • Two separate studies find dangerous complications following heart procedures for marijuana users.
  • Smoking marijuana (also known as cannabis) may significantly increase the risk of stroke and bleeding following procedures to open blocked arteries.
  • Similarly, marijuana users who had a heart attack or procedures to open blocked arteries were more likely to be readmitted to the hospital for a second heart attack or cardiac procedure than non-users.

Embargoed until 4 a.m. CT/5 a.m. ET Monday, Nov. 9, 2020

DALLAS, Nov. 9, 2020 — Smoking marijuana increases the risk of complications after cardiovascular procedures, and marijuana users who had a heart attack or cardiac intervention were more likely to be readmitted to the hospital for recurrent heart attacks or coronary procedures, according to two preliminary studies to be presented at the American Heart Association’s Scientific Sessions 2020. The meeting will be held virtually, Friday, November 13-Tuesday, November 17, 2020, and is a premier global exchange of the latest scientific advancements, research and evidence-based clinical practice updates in cardiovascular science for health care worldwide.

Using marijuana (also known as cannabis) is becoming more prevalent in the U.S., as numerous states have legalized it for recreational or medicinal use. However, research indicates marijuana has substantial risks and no benefits for cardiovascular health, and little is known about the safety of smoking marijuana for people with heart disease, according to a 2020 American Heart Association Scientific Statement. Two new studies, by separate researchers, explored how marijuana use affects patients with cardiovascular disease.

Not So Harmless: Marijuana Use and In-hospital Outcomes After Percutaneous Coronary Intervention: Insights From the Blue Cross Blue Shield of Michigan Cardiovascular Consortium (Presentation P1916)

Michigan researchers investigated whether patients who smoked marijuana are at an increased risk of complications after percutaneous coronary intervention (PCI) procedures compared with those who did not smoke marijuana. PCI, which includes angioplasty and stent placement, is a non-surgical procedure to open a blocked heart artery and restore blood flow to the heart.

“As marijuana is becoming more accessible across the U.S., there is a need for rigorous research to better understand the effects of marijuana use on cardiovascular health,” said Sang Gune Yoo, M.D., internal medicine resident physician at the University of Michigan and lead author of the study.

Researchers used a state-wide registry of more than 113,000 patients in Michigan who underwent angioplasty from January 2013 to October 2016. Nearly 4,000 people, or 3.5% of those in the study, reported smoking marijuana within a month of a PCI procedure, however, they did not specify if the marijuana had been prescribed. Medical marijuana – prescribed use for a medical condition – has been legal in Michigan since 2008, and recreational marijuana was legalized in Michigan in 2018 (after the time period of this study).

Patients who smoked marijuana and underwent angioplasty were average age of 54, 79% male and 73% of them also smoked cigarettes. They had fewer traditional risk factors for heart disease, such as high cholesterol, diabetes or high blood pressure.

After adjusting for differences between patients who did or did not smoke marijuana, researchers found:

  • Smoking marijuana was associated with a higher risk of stroke after PCI. “However, this should be interpreted with caution due to the overall very low rate of stroke after PCI,” Yoo said.
  • Marijuana smokers had an approximately 50% increased risk of bleeding after PCI.
  • Patients who smoked marijuana had a decreased risk of acute kidney injury compared with those who did not smoke.
  • There were no significant differences in the risk of death or the need for blood transfusion between groups.

“Although people who smoke marijuana may be at higher risk for complications such as stroke and post-PCI bleeding, this should not deter patients who use or have used marijuana from pursuing potentially life-saving PCI procedures,” Yoo said. “As marijuana use continues to increase, medical professionals and patients should be aware of these increased risks of complications after PCI. Physicians should screen and counsel patients about marijuana prior to their procedure due to the risks of serious complications.”

Senior study author Devraj Sukul, M.D., M.S., an interventional cardiologist at the University of Michigan, noted that, “understanding whether the effects of marijuana are dose-dependent or related to the method of intake are two important limitations of this study and remain important questions for future research.”  

Co-authors with Yoo and Sukul are Milan Seth, M.S., Thomas Earl, M.D., Cyril Ruwende, M.D., Ph.D., Milind Karve, M.D.; Ibrahim Shah, M.D.; Thomas Hill, M.D.; and Hitinder S. Gurm, M.D. Author disclosures are in the abstract.

The Blue Cross Blue Shield Michigan Cardiovascular Consortium (BMC2) coordinating center is supported by a grant from Blue Cross Blue Shield of Michigan to the University of Michigan. The sponsor had no role in the study design or decision to publish this work.

Note: Session EP.APS.11 - Social and Behavioral Risk Factors for Cardiovascular Disease

Prevalence, Trends and Impact of Cannabis Use on Hospitalizations With Prior Myocardial Infarction and Revascularization (Presentation P380)

This multi-center study assessed the prevalence and impact of marijuana use on hospital admissions for patients with previous heart attacks and revascularization procedures. Revascularization refers to restoring blood flow to the heart and includes non-surgical interventions such as percutaneous coronary intervention (PCI) as well as coronary artery bypass grafting (CABG). CABG is a surgical procedure to restore normal blood flow to a blocked coronary artery.

Researchers examined the National Inpatient Sample, the largest publicly accessible database in the U.S., to assess the rate of hospital admissions in patients with a history of previous heart attack, PCI and/or CABG, and self-identified marijuana users and non-users from 2007-2014. The database, which includes about 8 million hospital stays each year, does not include details about smoking or eating or other forms of marijuana consumption. Numerous states legalized or decriminalized medical and/or recreational marijuana during the study’s time frame.

The analysis found:

  • a 250% relative increase in cannabis use among patients who had survived a heart attack or revascularization;
  • 67% of the heart attack survivors who used cannabis had a subsequent heart attack vs. 41% of non-cannabis users; and
  • cannabis users had higher rates of hospitalizations for recurrent PCI and CABG. 

Marijuana users were more likely to be middle aged (median age 52 compared to median age 72 for non-users); Black Americans (34% vs. 10% of non-users); and male (77% vs. 62% of non-users). In addition, cannabis users had significantly lower rates of high blood pressure, diabetes and high cholesterol, however, it is unclear why these risk factors were low.

“There was an alarming rise in the trend of cannabis use among patients who have already had a heart attack or coronary revascularization procedure during the study period,” said the study’s lead author Rushik Bhuva, M.D., a cardiology fellow with the Wright Center for Community Health in Scranton, Pennsylvania. “Another concerning finding was that the frequency of recurrent heart attacks and cardiac interventions was 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,” said Bhuva. “In addition, the role of medicinal cannabis, its benefits and potential risks with regards to cardiovascular management need to be validated in larger studies.”

Study limitations included inability to access the mode and dose of cannabis consumption and lacking information about the time from cannabis use to cardiac event, whether use was recreational or medicinal and the lack of patient-level clinical information.

Co-authors with Bhuva are Rupak Desai, M.B.B.S.; Sandeep Singh, M.B.B.S.; Zainab J. Gandhi, M.B.B.S.; Faizan Ahmad Malik, M.D.; Virmitra G. Desai, M.B.B.S.; Vraj Patel, M.B.B.S.; Prince Khimani, M.B.B.S.; Falah Abu Hassan, M.B.B.S.; and Zarna Bambhroliya, M.B.B.S. Disclosures are in the abstract. There was no outside funding for the research.

Note: Session LF.APS.01 - Substance Use and CVD: Nicotine, Marijuana and Other Drugs

Additional Resources:

Statements and conclusions of studies that are presented at the American Heart Association’s scientific meetings are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers are available here, and the Association’s overall financial information is available here

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