Use of marijuana, meth, cocaine, and opiate could increase the risk of irregular heart rhythm

A large-scale study conducted by researchers from the University of California, San Francisco, (UCSF) on more than 23 million people has found that some commonly used and abused drugs may have a previously unknown adverse effect on heart health.

The mentioned effect is the risk of developing atrial fibrillation (AF), which is a potentially deadly heart-rhythm disorder and "the most common type of treated heart arrhythmia," according to the U.S. Centers for Disease Control and Prevention.

Increase in AF risk due to substance use

The research team examined data from diagnostic codes from California's every hospital admission, emergency room visit, and medical procedure between 2005 and 2015. In the end, they identified nearly one million people who developed AF during this period.

The UCSF scientists found that marijuana users were 35 percent more likely to develop AF later on. These rates increased to 61 percent in cocaine users, 76 percent in opiates users, and 86 percent in methamphetamine users.

“Despite exhibiting a weaker association with incident AF than the other substances, cannabis use still exhibited an association of similar or greater magnitude to risk factors like dyslipidemia, diabetes mellitus, and chronic kidney disease. Furthermore, those with cannabis use exhibited similar relative risk of incident AF as those with traditional tobacco use,” the researchers reported in the study paper.

“To my knowledge, this is the first study to look at marijuana use as a predictor of future atrial fibrillation risk,” said principal investigator Gregory Marcus, MD, MAS, a UCSF professor of Medicine with the Division of Cardiology.

Inhaled substances may contribute to the risk

The use of cocaine or methamphetamine has previously been linked to sudden cardiac death due to profound disruptions in the orderly electrical signaling and pumping within the heart’s other chambers, the ventricles. However, there is no demonstrated mechanism for how the use of marijuana triggers cardiac arrhythmias.

Even though the study was not planned to investigate marijuana constituents' possibility of increasing the AF risk, inhaled particles are probably a contributing factori, according to Marcus. He further added that inhaling particulate matter causes more inflammation, and inflammation triggers AF.

“It’s also intriguing to consider that inhaled substances travel directly from the lungs to pulmonary veins, which empty into the left atrium, and that the pulmonary veins and the left atrium are especially important in generating AF,” said Marcus.

Marcus intends to carry out controlled trials on humans in order to examine the effects of marijuana on cardiac rhythm more precisely and to further explore potential mechanisms via which use of other drugs may raise the risk of developing AF.

“Efforts to reduce substance abuse have the potential to reduce long-term cardiovascular complications associated with AF,” he said.

The study was published in European Heart Journal on October 17, 2022.