Adults who regularly smoked or vaped cannabis had fewer cardiac ectopic beats on days they were randomly assigned to inhale cannabis than on days they abstained, according to a randomized crossover trial.

The findings were driven by a reduction in premature atrial contractions. The study, published in the Journal of American College of Cardiology, also demonstrated no significant difference in premature ventricular contractions, physical activity, sleep duration, or mean glucose with cannabis use.

Prior observational studies have produced conflicting findings regarding cannabis use and cardiovascular effects, and researchers caution that this trial does not affect current practice or indicate newfound safety in smoking cannabis.

Nevertheless, the findings should spur additional research in the field, said Gregory Marcus, MD, MAS, study investigator and endowed professor in atrial fibrillation research at the University of California, San Francisco.

“Relationships between random assignment on heart rate variability were significant and consistent, likely providing good evidence,” Marcus said.

Study Structure

The trial included adults who smoked or vaped cannabis on a regular basis and did not have a history of cardiac arrhythmias. Researchers assigned participants to either inhale or abstain from cannabis daily for 14 days. They determined adherence with time-stamped Zio patch button presses at the time of cannabis use, daily surveys, and salivary mass spectrometry.

Daily cardiac ectopy — defined as daily premature atrial contractions and premature ventricular contractions — served as the primary outcome measure.

The researchers assigned 108 participants (mean age, 32 years; 59% women; 37% non-Hispanic White) to 713 days of inhaling cannabis and 616 days of abstinence. They noted an imperfect adherence to randomization but one that generally supported assignment adherence.

Drop in Premature Atrial Contractions

Data showed that inhaled cannabis led to a 9% reduction in ectopic beats (rate ratio [RR], 0.91; 95% CI, 0.85-0.98; P = .02), corresponding to an adjusted difference of 15 fewer ectopic beats per day. The rate of daily premature atrial contractions also fell (RR, 0.90; 95% CI, 0.82-0.97; P = .012), whereas premature ventricular contractions did not significantly change.

Moreover, each cannabis inhalation yielded a 2% reduction in ectopic beats (RR, 0.98; 95% CI, 0.97-0.99; P = .043). Step counts, sleep duration, and glucose levels did not significantly differ between groups.

The investigators highlighted several limitations in addition to imperfect adherence to randomization, including heterogeneous cannabis products, possible withdrawal effects, and the relatively young population with generally low frequencies of ectopy.

Clinical Impact ‘Minimal’

For Quinn R. Pack, MD, MSc, associate professor at the UMass Chan Medical School — Baystate Cardiology in Springfield, Massachusetts, the results have minimal immediate practical impact and should mostly prompt questions for future research.

“I strongly discourage any clinician from thinking that this study creates a reliable evidence base for a therapeutic effect for cannabis in patients with atrial ectopy,” said Pack, who was not involved in the study.

“Effect sizes were small and seem unlikely to be clinically significant. The population was young and the burden of atrial ectopy was minimal compared with the patients we often see in clinic,” he said.

Marcus also expressed caution, adding that he is hesitant to extrapolate any firm conclusions that might be immediately translated into clinical practice.

“However, users of cannabis should recognize there appear to be meaningful effects on the cardiovascular system,” he said. “And at least among frequent cannabis users, there did not seem to be any identifiable differences related to sleep, physical activity, or blood glucose. Whether indeed there are some constituents of cannabis that truly help suppress arrhythmias requires further study.”

Risk vs Benefit

Although research may eventually find tetrahydrocannabinol to have therapeutic effects and a role in clinical medicine, Pack noted that the data on smoking marijuana through combustion show strong signals for harm.

Consequently, he said, “the potential, small theoretical benefits of smoked marijuana use are, in my opinion, far outweighed by the well-described and negative cardiovascular effects of smoked marijuana on major adverse cardiac events as described in the literature.”

Marcus and Pack reported no relevant financial relationships.

Brian Ellis is a freelance writer and editor who lives in Southwest Virginia.