Alarming link between marijuana and increased heart risk

By Dr. Liji Thomas, MDJan 20 2020

Marijuana use is rising steadily across the US as more and more states enact laws making it a legal recreational and medicinal agent. However, a new study underlines the fact that this is, in fact, playing with an unknown substance, which may cause serious bodily harm.

The review article, published in the Journal of the American College of Cardiology, shows that more than 2 million adults who currently have heart or vascular disease gave a history of being currently on marijuana products, or having used them in the past.

Image Credit: Craig F Scott

The problem with marijuana use

Marijuana is a hemp plant product and is a schedule I drug under the U.S. Drug Enforcement Agency regulations. This means that it cannot be readily bought for use in research settings. In fact, scientists have repeatedly complained about the many levels of approval required before they can procure a supply of this substance for research use, ranging from local to federal tiers. On the other hand, recreational and medicinal users have ready access to the drug.

This anomaly means that individuals use this drug freely under the above conditions, provided the state in which they use it has legalized its use. On the other hand, virtually no scientific evidence about its effects on the body’s working, based upon randomized clinical trials, is available, due to the sheer unavailability of the drug. Such trials are the gold standard of medical intervention research. In the absence of such data, scientists have resorted to historical comparisons: they compare the numbers of people with various health conditions in different states both before and after the legalization of marijuana.

What is known

Previous observational studies have already pointed out the connection between the use of this drug and multiple cardiovascular issues. This includes the occurrence of strokes, arrhythmia and conditions that reduce the heart’s pumping efficiency. With increasingly widespread use, epidemiological studies on the large-scale or population level will help to understand how much cardiovascular risk is attributable to marijuana.

The study and findings

In the present study, the researchers searched data from the National Health and Nutrition Examination Survey (NHANES) dataset to find out how many patients with cardiovascular disease had or were currently using marijuana.

As a beginning, the researchers consulted pharmacologists and cardiologists to find out how exactly higher marijuana use affected the heart and blood vessels. They found that marijuana as well as its derivatives and components have different types of activity on the heart and blood vessels, but also interact with common cardiology drugs used in heart patients.

They also outlined the four known areas of marijuana-related heart risk:

• Smoking-induced heart damage because cigarette smoke and marijuana smoke contain many of the same toxic substances
• Obstruction of the coronary arteries, because marijuana smoking causes the heart to beat faster, increases the blood pressure and can even set off a heart attack as a result
• Irregular heart rhythms can occur in association with marijuana use, including atrial fibrillation which is associated with strokes and heart attacks
• Strokes and other vascular events in the brain are 3 times more frequent in marijuana smokers and those who vape it. The study showed that 17% of about 330 stroke patients below the age of 45 years smoked the drug.

Their final conclusion was that about 2.3% of the about 90 million adults with self-reported marijuana use had this condition. This comes to over 2 million adults. Since this study was conducted, more states have passed laws allowing marijuana use for medical or recreational purposes. This may have pushed up the total number of adult users still further.

Reflecting on the results, researcher Muthiah Vaduganathan says, “We're experiencing an epidemiological shift. More patients are curbing their cigarette smoking, and we're seeing big improvements in cardiovascular health for those who quit. In contrast, we're seeing an accelerating use of marijuana and now, for the first time, marijuana users are exceeding cigarette smokers in the U.S. We now need to turn our attention and public health resources toward understanding the safety profile of its use.”

One major concern, according to co-researcher Ersilia M. deFilippis, is that many patients with cardiovascular disease are also taking medications that could cause unforeseeable complications when combined with this drug. This is why, she says, “we need more data so that we can better counsel providers as well as patients.”

The conclusion

The study authors strongly recommend that physicians who see and treat heart and stroke patients ask them about marijuana use since this can influence the use of other medication. They advise consulting with a pharmacist before a prescription for a statin or an anticoagulant, for instance, is given, so that potentially dangerous interactions are ruled out. This is because both these medications and marijuana are broken down using the same enzymes of the cytochrome P450 family, which means that with higher levels of marijuana, the other substances tend to queue up for their turn. They also insist that patients and physicians talk openly about the possible risks to the heart and blood vessels of using the drug.

Says Vaduganathan, “Patients often ask us about the safety of marijuana use and we're pressed to offer the best scientific evidence. Our current approach is that patients who are at high risk of cardiovascular events should be counseled to avoid or at least minimize marijuana use, and that rigorous scientific research should be conducted to further inform recommendations for patient care.”