Posted on 05/08/2018

BOSTON, MA--According to new research, smoking marijuana may not be associated with an increased risk of ventricular fibrillation (VF) and ventricular tachycardia (VT) following an acute myocardial infarction (AMI), or heart attack. The study also reported that marijuana users had a decreased risk of atrial fibrillation (AFib) and in-hospital mortality. The results are scheduled to be presented on Thursday, May 10 at Heart Rhythm 2018, the Heart Rhythm Society’s 39th Annual Scientific Sessions. 

Recent federal data reported a stunning 455 percent increase in marijuana consumption among U.S. adults ages 55-64 years and 333 percent in ages over 64 years between 2002 and 2014 [1]. In fact, one in eight Americans say they smoke marijuana [2]. While results of previous studies show links between cannabis use and increases in heart rate and blood pressure, little is known about the cardiac-related effects for heart arrhythmias including VF and VT. VT is a very fast but regular heart rhythm that can lead to VF, which is fast and irregular and can cause sudden cardiac arrest. 

The study compared clinical profiles and in-hospital outcomes between reported marijuana users vs. non-users from 1994 to 2013. The primary endpoint was VT/VF or cardiac arrest and the secondary endpoint was atrial fibrillation or mortality. The patient group included people between the ages of 18-70 years with a primary diagnosis of AMI (ICD-9-CM code 410.xx) from eight states including California, New York, New Jersey, Vermont, New Hampshire, Colorado, Texas, and West Virginia. Patients who used cocaine, methamphetamine or alcohol were excluded from the study. Variables included in a step-forward multivariate logistic regression model included age, race and cardiac risk factors. 

In total, 3,854 of 1,273,897 patients admitted with AMI reported marijuana use. Findings from the study show marijuana users tended to be younger, male and less likely to have coronary artery disease (CAD) or coronary risk factors than non-users. Primary endpoints show that 9.7 percent (n=374) marijuana users and 9.7 percent (n=122,797) non-users experienced VT/VF or cardiac arrest. Secondary endpoints show that 4.5 percent (n=173) marijuana users vs. 8.7 percent (n=110,153) non-users had AFib, and 4 percent (n=135) vs. 6 percent (n=75,311) died, respectively. Despite there being no difference in the risk for VT/VF, researchers found in-hospital mortality was lower in marijuana users and a trend toward decreased risk of AFib was lower in marijuana users. 

"The legalization of marijuana is spreading quickly across the U.S. resulting in more people using it, but we still don’t know the true, long-term impact it has on one’s heart health. Our study is the first to examine the relationship between marijuana use after a heart attack and various arrhythmias and we did not see a negative connection," said senior author Christine Tompkins, MD, assistant professor of cardiology medicine at University of Colorado School of Medicine. "We are just one step closer to a better understanding of the various heart effects of marijuana, so that we are able to take the necessary actions to provide optimal patient care." 

The authors have noted that future studies are warranted to further understand the temporal relationship of marijuana and arrhythmias in patients with chronic ischemic heart disease, and are actively involved in a prospective observational study. They have also expressed interest in understanding the effects of marijuana in other chronic cardiac conditions, such as congestive heart failure and hypertension. The authors emphasize a need to understand how marijuana affects the heart so as to provide patients with informed choices, particularly since use in adults over the age of 50 years is increasing exponentially. 

SOURCE: Heart Rhythm Society