Over 2 million people with heart disease have used marijuana, finds study suggesting alarming link between the two
More than two million people with heart disease are currently using marijuana or have used marijuana previously, according to a review which suggests a potential and disturbing link between the substance and increased heart risk. Calling the finding "eye-opening", lead author Dr. Muthiah Vaduganathan from Brigham and Women's Hospital's Heart and Vascular Center in Boston says the review suggests that smoking marijuana carries many of the same cardiovascular health hazards as smoking tobacco.
The researchers say many “cardiotoxic chemicals” found in cigarettes are also found in marijuana smoke. “While the level of evidence is modest, there's enough data for us to advise caution in using marijuana for our highest-risk patients, including those who present with a heart attack or new arrhythmia, or who have been hospitalized with heart failure,” says Dr. Vaduganathan.
The researchers say while more data is needed, the evidence from the review indicates that marijuana use has been associated with coronary artery disease, arrhythmia, cardiomyopathy, and more.
According to the review, studies have identified marijuana smoking as a potential trigger of heart attacks, and marijuana use is not infrequently detected in adults who have experienced heart attacks at an early age (under 50). Cannabis inhalation can increase heart rate and blood pressure and maybe a trigger of a heart attack, explains the team.
Surveys have found that marijuana smokers were three times more likely to experience a cerebrovascular event, such as a stroke. Among 334 patients younger than 45 who had experienced a stroke, 17% were cannabis users. “It is thought that smoking marijuana may increase cellular stress and inflammation, which are known to be precipitating factors for coronary artery disease and heart attacks. Cerebrovascular events, including strokes, have also been associated with marijuana use. It is believed that marijuana may induce changes in the inner lining of blood vessels or alter blood flow," says the study.
According to the researchers, marijuana can also interact with drugs used to treat heart disease, including statins and blood thinners. Researchers believe that cannabinoids may increase the activity of these prescribed drugs in the body, though limited data are available to guide physicians in adjusting the dose to compensate for marijuana use.
For example, the team found that statin levels can increase in the blood when used together with marijuana because both are metabolized through a network of liver enzymes. Levels of blood thinners such as warfarin can also be expected to increase when used together with marijuana.
“Cannabinoids inhibit certain enzymes in the body, which affects the metabolism of many drugs for heart disease, including antiarrhythmics, statins, calcium-channel blockers, beta-blockers, and warfarin,” says the study published in the Journal of the American College of Cardiology.
Marijuana use on the rise
Marijuana use is on the rise as more US states legalize it for medicinal and recreational purposes. According to the research team, it is estimated that approximately 90 million American adults have used the drug at least once in their life, and more than 39 million have used the drug in the past year.
"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 US. We now need to turn our attention and public health resources toward understanding the safety profile of its use,” says Vaduganathan.
Marijuana is classified as a Schedule I drug by the US Drug Enforcement Agency, meaning that its use in research is highly restricted and researchers must navigate approvals through local, state and federally agencies. This means that even as individual states legalize its use, randomized, clinical trials to understand its health effects are not feasible, given the number of restrictions in place, says the study.
It says, “However, researchers can use real-world data to study its effects, for instance, by comparing before-and-after statistics on health in states where marijuana has been legalized for recreational use, medical use or both. As marijuana use increases in the US, large epidemiologic studies may clarify the relationship between marijuana and cardiovascular risk.”
The review
The research team examined data from the National Health and Nutrition Examination Survey (NHANES) to estimate marijuana use among US patients with cardiovascular disease. The review provides detailed tables of many drugs administered for various cardiovascular conditions, with the anticipated effects of marijuana on each one.
The team estimated that 2 million or 2.3% of the 89.6 million adults who reported marijuana use had cardiovascular disease. This includes recreational use and approved medical uses, such as human immunodeficiency virus-related weight loss, treatment of seizure disorders, or chemotherapy-associated nausea and vomiting.
"In addition to the 2 million marijuana users with diagnosed cardiovascular disease, many more may be at risk. With many adolescents and young adults turning to marijuana, it is important to understand the cardiovascular implications they may face years down the line," says Dr. Ersilia DeFilippis, a second-year cardiology fellow at Columbia University Irving Medical Center and NewYork-Presbyterian.
According to the researchers, the potency of marijuana -- the percentage of tetrahydrocannabinol (THC) contained in the plant -- has steadily increased over the past 30 years, from about 4% in the mid-1990s to 12% in 2014. However, most scientific studies of cannabis tested products with THC levels between 1.5% and 4%.
"Higher potency may translate into greater effects on the conduction system, the vasculature, and the muscle of the heart. It also highlights the need for real-world data given the variety of marijuana products and formulations available for purchase," says DeFilippis.
THC is the most psychoactive chemical in marijuana, but marijuana also contains more than 100 compounds, called cannabinoids, that are chemically related to THC.
“Receptors for cannabinoids are highly concentrated in the nervous system but also can be found in blood cells, muscle cells, and other tissues and organs,” the findings state.
The reviewers recommend that cardiologists screen their patients for marijuana use, asking them how often and how much they use.
“Asking patients about marijuana use may help in risk assessment. Besides, we know that marijuana use affects the metabolism of many common cardiac drugs. To make sure patients are getting therapeutic doses without untoward side effects, it is important for cardiologists to talk to their patients about marijuana use,” says DeFilippis.
Doctors should also ask patients about how they use marijuana, says the study. "Vaping marijuana is becoming more and more common, and we know vaping marijuana increases the pharmacological effects of the drug," says Vaduganathan.
The team says patients at risk of cardiovascular events should be counseled to avoid or minimize marijuana use until further data are available.