Cannabis: It can be a heartbreaker

June 11, 2019

While some advocates contend marijuana is harmless, others are cautioning its long-term risks and benefits haven’t yet been carefully studied. One of the few things we do know is cannabis has notable effects on the heart, which, for some, are resulting in cardiovascular emergencies including heart attack, arrhythmias and stroke.

Cannabis is a very complex plant. Containing over 400 individual chemicals, the range of effects cannabis is known to have on the cardiovascular system includes raising resting heart rate, dilating blood vessels, and making the heart pump harder.

While these effects generally do not pose a significant threat to healthy individuals who possess a low cardiovascular risk, they should be a red flag for those who have a history of heart disease or are at high risk of cardiac complications.

Dr. Paul Oh (left) poses for a photograph with Dahlia Kurtz prior to their taped radio interview. The segment aired on an episode of The Goods with Dahlia Kurtz, a CFRA 580 News Talk radio program.

“If you are older or have established heart issues, your ability to withstand sudden changes in heart rate, blood pressure or cardiac arrhythmias is already challenged,” says Dr. Paul Oh, Medical Director and GoodLife Fitness Chair with the University Health Network’s Cardiac Rehabilitation Program, and Associate Professor of Clinical Pharmacology at the University of Toronto. “Hospitalization for cardiac distress following marijuana use is not uncommon in such cases.”

As both recreational and medicinal marijuana increases in popularity in Canada and elsewhere, reports linking it with cardiovascular emergencies such as heart attack, arrhythmias, heart failure, stroke and cardiac arrest in otherwise healthy young individuals are also on the rise.

In particular, cannabis use appears to increase the risk of a rare heart muscle malfunction called takotsubo where the heart’s muscles suddenly balloon and weaken, reducing its ability to pump blood. While regular takotsubo, or ‘broken heart syndrome’ typically affects older women, marijuana-using takotsubo sufferers are more likely to be young men.

“In the US, where in 28 states you can legally use marijuana for a range of health problems, a growing number of young, healthy men are showing up in emergency rooms with what looks like heart attacks associated with recent cannabis smoking,” says Dr. Oh, who recently spoke about cannabis use and its effects on the heart at the Toronto-Ottawa Heart Summit, jointly held with the 7th International Ottawa Heart Conference: Big Data in Cardiovascular Disease. “We don’t understand why this is happening. Hopefully, future research will shed some light on why cannabis use seems to present an unusual cardiac risk for takotsubo in young men.”

With the liberalized approach to marijuana – including the legalization of cannabis edibles in Canada in the fall of 2019 – we are bound to see higher-quality scientific research build a more robust medical literature on the effects of marijuana and heart health. Until then, experts like Dr. Oh urge more efforts are needed to increase public awareness about the cardiovascular risks associated with cannabis use.

Our entire society is walking into unchartered territory.

- Dr. Peter Liu, Chief Scientific Officer and Vice President of Research, Ottawa Heart Institute

“Our entire society is walking into unchartered territory,” says Dr. Peter Liu, Chief Scientific Officer and Vice President of Research at the Ottawa Heart Institute. “We need to work together to learn the unknowns, including any unwanted side-effects cannabis may cause on its own or when it is combined with other medications.”

“Open and honest dialogue between doctors and their patients is a good place to start,” he adds. “If it wasn’t part of the conversation before, any marijuana use needs to be part of the conversation now.”