Cannabis May Up Heart Risk
Cannabis use may increase the risk of heart failure, stroke, or myocardial infarction, according to a pair of large observational studies presented at the American College of Cardiology’s Annual Scientific Session in Washington, DC.
Twenty-eight states and the District of Columbia have now legalized the medical or recreational use of cannabis. But with limited research to date, the public health implications are unknown.
Case reports of heart failure or stroke in young otherwise healthy individuals who use cannabis have raised concern that the drug might have some adverse effects on the heart. Aditi Kalla, MD, a cardiology fellow at the Einstein Medical Center in Philadelphia, explained that several case reports have described heart failure in young patients who had used high enough doses of marijuana to develop cyclic vomiting. In these cases, stopping use of cannabis reversed the condition and screening tests for other possible causes came up empty.
In addition, at least 2 cases of simultaneous stroke and heart attack have been reported in young individuals apparently caused by blood clots after using substantial amounts of marijuana.
“Cannabis may increase the activity of certain clotting factors and may also affect platelet activity that leads to heart attacks and/or strokes in these patients,” she said.
To better assess the heart risks associated with cannabis, Kalla and her colleagues compared the rates of cardiovascular events in 316 397 cannabis users and ≈20.5 million nonusers by using data from the National Inpatient Sample. The analysis was limited to individuals 18 to 55 years old who were discharged from hospitals between 2009 and 2010.
The study found an increased risk of heart failure (odds ratio, 1.1 [1.03–1.18]; P<0.01) and cerebrovascular accidents (odds ratio, 1.24 [1.14–1.34]; P<0.001) in cannabis users after adjusting for potential confounders.
“For every medication there is an intended effect and adverse effects,” Kalla said. “Our study highlights that cannabis has a potential adverse effect on the heart.”
A second study presented at the meeting by Ahmad Tarek Chami, MD, of Case Western University in Cleveland, analyzed data on 210 700 cannabis users and 10.3 million controls from a multi-institution database. They found that the 5-year cumulative incidence of myocardial infarction was higher among cannabis users (1.28% versus 0.89%; relative risk, 1.44 [95% confidence interval, 1.39–1.50]). It is interesting to note that the risk of a heart attack was especially high among younger individuals (relative risk 3.2 for those 25–29 years of age and relative risk 4.56 for those 30–34 years of age). The elevated risk persisted even when they adjusted for traditional heart risk factors. The authors suggest that additional studies are needed to confirm the results.
Some basic research has pointed to potential mechanisms for cannabis-related cardiac problems. There are cannabis receptors in heart cells, and they may affect the ability of the cells to contract, explained Kalla.
Kalla noted that more research is needed to assess the potential heart effects of cannabis. In particular, she said studies that examine the dose and form of cannabis use and that conduct a cardiac health assessment before first use would be helpful. She noted that, at the end of Prohibition, researchers studying alcohol’s health effects expected it to be harmful to the heart. But studies have shown that moderate amounts of alcohol can be cardioprotective, so it is possible that dose may also be important for marijuana.
“What we are hoping to find out is whether there is a cutoff at which cannabis affects the heart [negatively],” she said.
Based on the evidence so far, cardiologists may want to urge caution when advising patients about the use of cannabis.
“It is important for patients to be aware of the potential cardiovascular risks associated with cannabis use, because lifestyle modification plays a significant role in preventing and treating cardiovascular complications,” said Kalla.
Zika Linked to Arrhythmias
Infection with the Zika virus may cause arrhythmias and heart failure even in patients with no prior history of cardiovascular disease, according to a presentation at the American College of Cardiology’s Annual Scientific Session in Washington, DC.
The Zika virus’s link to severe birth defects has been well documented, but its wider effects on health are only beginning to be understood. Now, Karina Gonzalez Carta, MD, a cardiologist and research fellow at the Mayo Clinic and her colleagues show that some infected individuals with no prior history of cardiovascular disease develop arrhythmias and heart failure.
Since 2015, the Zika virus has rapidly spread throughout South and Central America, and has now gained a foothold in the United States with >5000 reported US cases and >38 000 reported cases in US territories, according to the US Centers for Disease Control and Prevention. Although most cases have occurred in travelers to countries where infections are more common, some cases of transmission in the United States have been documented.
“We know that other mosquito-borne diseases can affect the heart, so we anticipated the same might be true for Zika,” Carta said. For example, Dengue and Chikungunya cause cardiomyopathies and myocarditis.
So, Carta and her colleagues studied 9 Zika patients with cardiovascular symptoms from a clinic in Caracas, a Venezuelan city hard hit by the virus. The symptoms in all the patients appeared within 2 weeks after initial symptoms of Zika infection, which include fever, conjunctivitis, and rash. The patients were followed on average 6 months and all received clinical examinations, laboratory tests, imaging, and Holter studies.
All but 1 patient had arrhythmias and 6 had heart failure, 5 with reduced ejection fraction. One patient with heart failure was pregnant, and she had preserved ejection fraction with preeclampsia and a moderate to severe pericardial effusion.
“While we anticipated seeing cardiovascular effects of ZIKA, we were surprised by the severity of the findings,” Carta said.
The cause of these heart effects is not clear, but Carta suggested that direct viral effects on myocytes, inflammation, or immune responses could all cause damage. More study is needed to assess the prevalence of cardiac complications in patients with Zika.
In the meantime, she noted that physicians and the public need to be aware of the possibility of Zika-related heart complications.
“If travelers develop a fever and conjunctivitis, they should seek medical care as soon as possible,” she said. “If patients have fatigue or palpitations, they should get an echocardiogram.”
Circulation is available at http://circ.ahajournals.org.
- © 2017 American Heart Association, Inc.