- A randomized crossover trial examined the acute cardiovascular effects of inhaled cannabis among habitual users.
- There was a significant 9% reduction in premature heartbeats on days participants inhaled cannabis compared with days they abstained.
- The finding of reduced cardiac ectopy was questionable given major limitations of the trial, but the data did suggest that there was no increase in these heartbeats.
Defying expectations, regular cannabis users had fewer ectopic heartbeats on the days they reached for the joint or vape, a randomized crossover trial showed.
On days using cannabis, there was a significant 9% reduction in these extra or early heartbeats (median 13 per day on cannabis vs 13.8 per day off cannabis; rate ratio [RR] 0.91, 95% CI 0.85-0.98) among habitual cannabis smokers and vapers who had no history of clinically diagnosed cardiac arrhythmias.
While each cannabis inhalation was associated with a 2% reduction in ectopic beats (RR 0.98, 95% CI 0.97-0.99), Gregory Marcus, MD, MAS, of the University of California San Francisco, and colleagues noted that they were still wary of jumping too quickly to claim causality from this randomized trial.
“Given imperfect adherence, possible carryover, heterogeneous exposure, low baseline ectopy burden, and multiple exploratory analyses, the clinical implications remain uncertain,” they wrote in the Journal of the American College of Cardiology.
“Ultimately, the most conservative interpretation of these data may be the clear evidence that inhaled cannabis did not increase cardiac ectopy,” Marcus and team conceded.
Study participants were randomly assigned each day to inhale cannabis products or abstain completely via text messages for 14 days. Inhaled cannabis included smoked cannabis (joints, blunts, pipes, and bongs) and vaped cannabis. During follow-up, participants were equipped with a continuously recording ECG patch, a wrist-worn Fitbit activity tracker and sleep monitor, and a continuous glucose monitor for the first 10 days.
No significant differences were observed for step counts, sleep duration, or glucose levels.
“This study examined the acute effects of cannabis in people who use it regularly and was not designed to evaluate the long-term health consequences,” Marcus cautioned in a press release. “The overall health effects of inhaled cannabis may still be net negative, but these findings suggest there may be something about cannabis that can teach us more about the biological mechanisms that produce premature atrial contractions. That knowledge could eventually lead to new approaches for preventing or treating abnormal heart rhythms.”
Of note, the change in daily ectopy was driven by a decrease in daily premature atrial contractions (PACs), with a median of 7 on cannabis days versus 9.75 on off-cannabis days (RR 0.90, 95% CI 0.82-0.97), whereas premature ventricular contractions (PVCs) were unchanged on days using cannabis (median 3 vs 2.75; RR 1.01, 95% CI 0.91-1.12).
“To our knowledge, no previous randomized trial has demonstrated that any common exposure or lifestyle factor can influence PAC counts,” Marcus and colleagues wrote.
The finding naturally leads to the question of whether lower PAC counts amount to tangible protection from a full-blown cardiac arrhythmia.
“Although the current study did not assess AF [atrial fibrillation] as an outcome, previous research has shown that PAC frequencies in the general population were the single most potent predictor of AF,” the authors noted. “Indeed, eradication of PACs has been shown to prevent AF in select patients, and PACs, perhaps the most common arrhythmia, can themselves be bothersome and reduce quality of life.”
The study included 108 adults who regularly smoked or vaped cannabis and had no history of clinically diagnosed cardiac arrhythmias.
At baseline, average age was 32 years, and 59% were women. None of the participants had diabetes, and 8% had hypertension. The most commonly reported methods of cannabis inhalation were joints (63%) and vape cartridges (57%), ranging in frequency of use from one to four times per month to three times or more per day. Fewer than one in three participants smoked tobacco or vaped nicotine concurrently.
There were a total of 713 days randomized to inhaled cannabis and 616 days randomized to abstinence.
Based on a combination of time-stamped Zio patch button presses at the time of cannabis use, daily surveys, and salivary mass spectrometry, Marcus and colleagues determined that participants followed instructions to inhale or avoid cannabis on most days, with adherence deemed as “moderate.”
The authors acknowledged that there were plenty of caveats to the randomized study.
“For example, participants were not blinded to their exposure and were instructed to use their own cannabis products. This allowed for an assessment of the full inhaled cannabis experience that best recapitulated actual drug exposure and enhanced our ability to recruit and retain participants,” they wrote. “However, this also resulted in substantial heterogeneity in the types and amounts of cannabis consumed and a consequent reduction in precision in analyzing associations with specific constituents.”
Requiring participants to be frequent cannabis users may be a source of selection bias, they added, while the selection criteria further excluded anyone who had a history of AF or heart failure; had an implanted pacemaker or implantable cardioverter-defibrillator; had been prescribed beta-blockers, nondihydropyridine calcium-channel blockers, or Vaughn-Williams class 1 or 3 antiarrhythmic medications; or had a medical reason to avoid cannabis.
Importantly, the trial did not assess other effects of acute cannabis inhalation, nor did it collect data on alcohol consumption, a common co-intervention also linked to more PACs and PVCs.
The same research group previously reported that coffee consumption caused PVCs but not PACs.
