Marijuana Use Disorder and Arrhythmias: What Were They Smoking?

Brian Olshansky


Europace. 2021;23(8):1155-1156. 

Marijuana ('cannabis') use is widespread and even legal, in some locales. Aside from the well-known central nervous system effects, cannabis may be associated with arrhythmias including atrial fibrillation, atrioventricular block, even ventricular fibrillation, as reported in case series.[1,2] One investigation[3] from the National Inpatient Sample (NIS) considered 2 459 856 weighted hospitalized recreational marijuana users, of whom, during hospitalization, 2.7% had arrhythmias, including atrial fibrillation (1865/100 000), atrial flutter (346/100 000), supraventricular tachycardia (132/100 000), ventricular tachycardia (532/100 000), ventricular fibrillation (136/100 000), ventricular flutter (2/100 000), or 'Wolff-Parkinson-White' (80/100 000). In another report utilizing the NIS, of 570 556 patients with a primary discharge diagnosis of arrhythmias, 14 426 (2.53%) had 'cannabis-use disorder'[4] [a DSM (Diagnostic and Statistical Manual of Mental Disorders] classification representing a fraction of overall users[5]). Any relationship between marijuana use and arrhythmias in both studies, however, was uncertain and unconvincing. There was no comparator group in either study. Is a link between cannabis and arrhythmia just a pipe dream?

With a comparator, utilizing the NIS again, of 3 950 392 patients admitted with heart failure, the 17 755 (0.45%) cannabis users were less likely to have atrial fibrillation than a propensity-matched non-user group [19.08% vs. 21.39%; adjusted odds ratio (aOR): 0.87 (0.77–0.98); P = 0.0005].[6] Data supporting an antiarrhythmic effect from cannabis comes from cell cultures showing cannabidiol protects against high glucose-induced oxidative stress and cytotoxicity in cardiac voltage-gated sodium channels.[7] Good to know in the case of the munchies.

To help clear the smoke, in this month's Europace, Umapathi et al.[8] consider the prevalence of cardiac arrhythmias in 'cannabis use disorder related hospitalizations' in teenagers/young adults from 2003 to 2016 in the USA using NIS and KID (Kid's Inpatient Database). Of 876 431 'cannabis use disorder' weighted hospitalizations among teenagers, 4043 (0.46%) had arrhythmias—not a particularly dramatic percentage by any means. Although the outcome measure was 'burden of arrhythmias' in cannabis use disorder-related hospitalizations, the burden of arrhythmias was not determined (but their presence might have been).

The most frequent arrhythmia was atrial fibrillation (105/100 000 or 0.1%, a piddling number).[8] It is not clear how the arrhythmias were discovered or how, or if, they were related to cannabis abuse. Prolonged QT (value not discussed) is not an arrhythmia. Neither is Wolff–Parkinson–White Syndrome. Accessory pathways do not grow with cannabis as far as I know. What arrhythmias were present? Were they significant clinically? Were they related temporally to cannabis? One can only wonder: What were the authors smoking?

Of critical importance: there was no matched control population, who did not partake, to compare the risk of arrhythmias. The authors[8] contend that the control population was those with cannabis use disorder and no arrhythmia. Instead, a more correct control group would be a matched group of non-users. Do non-users have fewer or more 'arrhythmias'? From this article, we have no idea.

It is difficult, if not impossible, to know the prevalence or incidence of 'arrhythmias' in a non-user control population. There is no historical control to compare against either. While not an identical population, data from paediatric-age patients hospitalized in the cardiac intensive care unit indicate that 29% of admitted patients had one or more arrhythmias.[9] A prior history of arrhythmias was recorded in 4.8% of admissions.[9] In another study of 152 322, comprising 71 855 elementary school (age 5–6 years) and 80 467 junior high school students (age 12–13 years), rhythm disturbances rose with age and were present in 1.25% of elementary school and 2.32% of junior high school students.[10] Perhaps, cannabis is associated with lower risk of arrhythmias as it may be antiarrhythmic. We also have no idea if arrhythmias noted in Umapathi's[8] manuscript had any consequence.

The increased prevalence of arrhythmias from 2003 to 2016[8] does not have to do with cannabis since all included were cannabis users. Congenital heart disease, congestive heart failure, myocardial infarction, electrolyte disorders, hypertension and obesity predicted arrhythmias.[8] No surprise. Older patients had a higher prevalence of arrhythmias compared to younger teenagers but this is due to age rather than cannabis use disorder. The presence of arrhythmias based on location (southern region of the USA), Caucasian race, male sex, or insurance categorization[8] has nothing to do with cannabis use disorder; it has to do with demographics. Further, there was no way to determine a temporal relationship between marijuana use or dose and arrhythmias (or morbidity/mortality) during hospitalization.

What were the hospitalized patients smoking? While that is uncertain, it appeared that concomitant substances of abuse, namely, alcohol, tobacco, opiates, or cocaine were not associated with arrhythmias (aOR 1.023 P = 0.55).[8] These substances have been associated with arrhythmias.

With numerous limitations mentioned in their manuscript, the authors conclude that using a large administrative database provides 'useful insights into the risk of arrhythmias due to the impact of cannabis use disorder'.[8] Does it? They have not shown that toxicology screening for marijuana should be considered for any individual with a new-onset arrhythmia as they conclude. What were the authors smoking?

In a prior meta-analysis,[11] Richards et al. remarked: 'clinicians and nurses should inquire about acute and chronic cannabis use in their patients presenting with tachycardia, bradycardia, dysrhythmia, chest pain, and/or unexplained syncope. Patients who use cannabis should be educated on this deleterious association, especially those with underlying cardiac disease or risk factor'. Based on present data, I remain dazed and confused.

So…what does cannabis have to do with arrhythmias? The authors have not shown us. Although they posit that cannabis has arrhythmogenic properties, data, extending as far back as 50 years ago, repudiate this.[12]

A previous commentary[13] suggested paying attention to the possibility of arrhythmias due to cannabis use may prevent harm. Raising concern without evidence is an age-old, fear-mongering, tactic. There is a fine line between fear mongering and rightful concern. No doubt, some patients will get admitted to the hospital with arrhythmias who abuse marijuana but patients will definitely get admitted with arrhythmias who do not abuse marijuana.

When it comes to yet another manuscript raising the issue of arrhythmias and cannabis, it is time to stop blowing smoke and focus on evaluating and establishing valid and realistic relationships between arrhythmias and cannabis, if any exits. If there is a relationship, it will be important to determine how this affects outcomes. Until then, no data support any adverse relationship between cannabis and arrhythmias, but, until then, it is probably best not to inhale, nevertheless!