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Cannabis Use Linked With Heart Attack Complications, Studies Say

By Alexander Beadle

Published: Nov 10, 2020   
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Two new preliminary studies have found evidence linking cannabis use to dangerous complications for patients following heart procedures.

One study found that smoking cannabis may significantly increase the risk of complications such as strokes or bleeding, following non-surgical interventions to open blocked arteries. The other study uncovered “an alarming rise” in the trend of cannabis use among patients who had already experienced a heart attack or who had undergone a heart procedure in the past.

Both pieces of research are to be presented next week at the American Heart Association’s (AHA) Scientific Sessions 2020 event.

Although medical cannabis has been demonstrated as beneficial for other health conditions, the AHA says that cannabis use represents “substantial risks and no benefits for cardiovascular health,” with more research being needed to determine the extent and dose-dependency of these health risks.

Cannabis and heart attack

The first study sought to look at the prevalence and impact that cannabis use had on hospital admissions for patients with a history of heart attacks, or who had previously had a revascularization procedure to restore blood flow to the heart.

For the purposes of this study, the researchers included data from both surgical and non-surgical revascularization procedures, including coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI).

The researchers looked at data from the largest publicly accessible patient database in the US, the National Inpatient Sample, and focused on the hospital admissions data collected between 2007 and 2014. They found that two-thirds of heart attack survivors who self-identified as cannabis consumers in the patient data went on to have a subsequent heart attack, compared to only 41 percent of non-users. The researchers also uncovered a 250 percent relative increase in cannabis use among patients who had survived a heart attack or revascularization procedure.

“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, a cardiology fellow with the Wright Center for Community Health, Pennsylvania, in a statement. “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.”

The cannabis-using demographic leaning younger might also explain why the researchers observed lower rates of all-cause mortality for the cannabis-using group, the researchers hypothesize.

From the other demographic information they gleaned in the study, they recommend that more needs to be done to spread awareness of the risk of recurrent heart attacks among middle-aged, African-American, and male cannabis users. Clinicians are also encouraged to begin screening cannabis consumers within these demographics for other risk factors at an earlier age, to try and reduce the risk of developing heart problems.

“In addition, the role of medicinal cannabis, its benefits and potential risks with regards to cardiovascular management need to be validated in larger studies,” added Bhuva.

Cannabis users at higher risk of some post-surgical complications

The second preliminary study, led by researchers at the University of Michigan, looked more specifically at the outcomes for cannabis users who underwent a PCI procedure.

“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,” Sang Gune Yoo, an internal medicine resident physician at the University of Michigan and lead author of the study, told the AHA.

The PCI procedure often consists of angioplasty, which involves a balloon-tipped catheter being inserted into a narrow or blocked artery and inflated to widen it, and then the insertion of a stent to more permanently widen the blood vessel and improve blood flow.

From a state-wide registry of more than 113,000 Michigan patients who underwent a PCI procedure between January 2013 and October 2016, they identified nearly 4,000 who reported smoking cannabis within a month of the procedure. Between these dates only medical cannabis consumption was legal in Michigan, though the patient data available did not specify whether the cannabis being used had been prescribed by the patient’s physician.

Upon further analysis, the researchers found that smoking cannabis was associated with a higher risk of stroke following PCI, although the overall risk of stroke as a complication was still very low. Cannabis users did however have a 50 percent increased risk of bleeding post-procedure.

Interestingly, the cannabis consumers had an overall decreased risk of experiencing acute kidney injury following the procedure as compared to non-smokers, and the overall risk of mortality and need for blood transfusions did not significantly differ between either group.

“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 researchers also noted other interesting demographic information about that the patients who smoked cannabis and underwent a PCI procedure. They had an average age of around 54, around four-fifths were male, and nearly three-quarters of the patients also smoked cigarettes. Notably, they also generally presented with fewer traditional risk factors for heart disease, such as high cholesterol.

Understanding how cannabis use affects recovery from cardiac interventions is an important next step for the field, the researchers say. Senior study author and interventional cardiologist Devraj Sukul also added 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.”


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