Marijuana users who had a heart attack or cardiac intervention are more likely to be readmitted to the hospital for recurrent heart attacks or coronary procedures, according to 2 preliminary studies to be presented at the American Heart Association’s Scientific Sessions 2020.

Cannabis use is becoming much more prevalent in the United States, as several additional states recently legalized it for recreational or medicinal use. However, use of the drug has substantial risks and no demonstrated benefits for cardiovascular conditions, and little is known about the safety of smoking marijuana for individuals with heart disease. According to a press release, 2 new studies aimed to expand this body of knowledge.

“As marijuana is becoming more accessible across the US, there is a need for rigorous research to better understand the effects of marijuana use on cardiovascular health,” said lead study author Sang Gune Yoo, MD, in a press release.

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

The team used a statewide registry of more than 113,000 patients who underwent angioplasty between January 2013 and October 2016. According to the results, 3.5% of these participants reported smoking marijuana within a month of their PCI procedure, although they did not specify whether the cannabis had been prescribed. Medical marijuana has been legal in Michigan since 2008 and recreational marijuana was legalized in 2018.

Patients who reported smoking marijuana were an average age of 54 and 79% were male, of whom 73% 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, the team found that smoking marijuana was associated with a higher risk of stroke after PCI, although they urged caution with these data due to the very low rate of strokes following PCI procedures.

Furthermore, marijuana smokers had an approximately 50% increased risk of bleeding after a PCI procedure. Interestingly, the researchers found that patients who smoked marijuana had a decreased risk of acute kidney injury compared with patients who did not smoke. Further, there were no significant differences in the risk of death or the need for a 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.”

The second study investigated the prevalence and impact of marijuana use on hospital readmissions for patients with previous heart attacks and revascularization procedures. Revascularization involved restoring blood flow to the heart and includes non-surgical interventions such as PCI as well as coronary artery bypass grafting (CABG), which is a surgical procedure to restore normal blood flow to a blocked coronary artery.

Investigators examined the National Inpatient Sample to assess the rate of hospital admissions in patients with a history of previous heart attack, PCI, CABG, or a combination of all 3, and self-identified marijuana users and non-users between 2007 and 2014. The data base notably does not include details about smoking, eating, or other forms of marijuana consumption.

The team found a 250% relative increase in cannabis use among patients who had survived a heart attack or revascularization, although 67% of the heart attack survivors who used cannabis had a subsequent heart attack compared with 41% of non-cannabis users. Cannabis users also had higher rates of hospitalizations for recurrent PCI and CABG. Marijuana users were more likely to be middle aged, Black, and male, and they had significantly lower rates of high blood pressure, diabetes, and high cholesterol, although it is unclear why these risk factors were low.

“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 lead author Rushik Bhuva, MD, in a press release. “In addition, the role of medicinal cannabis, its benefits, and potential risks with regards to cardiovascular management need to be validated in larger studies.”

REFERENCE
Marijuana use associated with complications after heart attack or procedures [news release]. American Heart Association Scientific Sessions 2020; November 9, 2020. https://newsroom.heart.org/news/marijuana-use-associated-with-complications-after-heart-attack-or-procedures?preview=8804. Accessed November 10, 2020.