There is other evidence that smoking marijuana can be dangerous for people with heart disease, according to two new studies presented recently at the American Heart Association’s scientific sessions. But in an unexpected twist, people who use cannabis were less likely to experience sudden kidney failure, the researchers found.
One study found that patients who smoked marijuana and underwent angioplasty to clear blocked arteries were more likely to suffer strokes and bleeding after the non-surgical procedure than those who didn’t use the herb. The second study concluded that patients who had survived a heart attack and used marijuana were more likely than those who had not used cannabis to have a subsequent heart attack. Both studies were published on Monday.
Marijuana is becoming more accessible and patients should be aware of the increased risk afterwards [angioplasty]”Said lead author of the study, Dr. Sang Gune Yoo, an internal medicine resident at the University of Michigan.” While these are risks to be aware of, they should not discourage patients from getting this life-saving procedure. “.
In fact, four other states legalized recreational marijuana during the 2020 election, bringing the total to 15 plus the District of Columbia. Additionally, 34 states, plus DC, have made medical marijuana legal.
The new findings are another example of why we need more studies on the effects of cannabis on heart health and the rest of the body, Yoo said, noting that its classification by the federal government as a Schedule 1 drug has hindered scientific research.
The research is particularly relevant for older Americans. Heart disease is the number 1 killer in the United States, and the Centers for Disease Control and Prevention estimates that approximately 805,000 Americans have a heart attack each year. Most, or 605,000, are first-time heart attacks. Every year, hundreds of thousands of patients in the United States have coronary angioplasty, a procedure for blocked arteries that improves blood flow to the heart, according to the American Heart Association. Many of these patients also receive stents, a small wire mesh tube that helps keep the artery open.
To take a closer look at the impact of marijuana on angioplasty outcomes, Yoo and his colleagues looked at data on 113,477 Michigan patients, 3,970 of whom self-identified as marijuana users. After matching 3,903 users with 3,903 nonusers, the researchers found that more weed smokers experienced bleeding (5.2% vs 3.4%) and strokes (0.3% vs 0.1%).
An interesting finding that the authors couldn’t explain was that marijuana users were less likely to experience sudden kidney failure.
Is it THC or smoke?
In the other study, which analyzed information from a national database, the researchers found that among patients who had an arterial cleansing procedure after a heart attack, those who used marijuana had a higher rate of subsequent heart attacks than to those who don’t use cannabis, or 7.2 percent versus 4.5 percent. This study also had an intriguing finding: heart attack risk factors – including hypertension, diabetes, and high cholesterol – were significantly lower in cannabis users.
Experts contacted by NBC News have had mixed reactions to the new reports.
“I have spent the past 25 years studying the effects of marijuana and THC [the psychoactive component in cannabis], and I think the Yoo study raises some important questions, especially as we have seen more and more reports of cardiovascular events occurring in the context of marijuana, “said Dr. Deepak Cyril D’Souza, professor of psychiatry at Yale University. School of Medicine. “This is an interesting document.”
One question the study can’t answer is whether the greatest risks come from marijuana, the THC in marijuana, or the smoke that comes from burning a plant-based product, D’Souza said.
“In our THC studies, we found a very robust increase in heart rate and an effect on blood pressure that can be quite profound,” D’Souza said, adding that blood pressure increased in people who were lying down. “Our studies typically included young, healthy people. Extrapolating to someone who is older and has cardiovascular or other medical problems, it could be problematic if they used marijuana. “
Looking at the totality of the two studies, they appear to contain some contradictory results, said Dr. Peter Grinspoon, a cannabis expert, instructor at Harvard Medical School and board member of Doctors for Cannabis Regulation. On the one hand, Grinspoon said, researchers are reporting increases in strokes, bleeding and second heart attacks in those who use cannabis, but on the other, they are reporting improvements in cardiovascular risk factors, such as hypertension, high cholesterol and diabetes.
Grinspoon was particularly struck by the lower rate of kidney failure among those who used marijuana in the Yoo study.
“With their measurements, they have actually shown that cannabis reduces kidney damage, which should be a huge headline in itself,” he said.