Chronic cannabis smoking linked to high-grade heart block requiring pacemaker in 26-year-old | Research

The takeaway

A 26-year-old chronic cannabis smoker developed high-grade atrioventricular block with a novel finding of prolonged HV interval on electrophysiology study, requiring permanent pacemaker implantation.

Cardiologists, young cannabis users, and anyone interested in rare cardiovascular effects of chronic cannabis use.

First electrophysiologic localization of cannabis-associated conduction block

What the researchers found

Electrophysiology study revealed high-grade supra-Hisian AV block with prolonged His-ventricular interval in a young man with chronic cannabis use and no other identifiable cause. The arrhythmia did not resolve after three months, and a dual-chamber pacemaker was required. This is the first report of electrophysiologic localization of cannabis-induced conduction block.

Why it matters

While cannabis-associated tachyarrhythmias are well-documented, bradyarrhythmias are rare. The prolonged HV interval suggests cannabis may directly affect the cardiac conduction system rather than just increasing vagal tone, as previously assumed.

The numbers in context

Age 26; heart rate 42 bpm at presentation; positive for THC metabolite 11-Nor-9-carboxy-THC; supra-Hisian block with prolonged HV interval; dual-chamber pacemaker implanted; arrhythmia persisted at 3-month follow-up

How the study worked

Clinical case report of a 26-year-old male with chronic cannabis smoking who presented with dizziness and syncope. ECG, electrophysiology study, urinary THC metabolite testing, and follow-up evaluation were performed after ruling out other causes.

What this study cannot tell us

Single case report. Cannot definitively prove cannabis caused the conduction block. Possible confounders from unknown adulterants. No long-term follow-up beyond three months.

How to read the evidence

Single case report with novel electrophysiology findings, but no ability to establish causation or prevalence.

When this study was published

Published in 2021.

The bigger picture

This case challenges the assumption that cannabis-related bradycardia is solely vagally mediated. The prolonged HV interval and persistent nature of the block suggest potential direct toxic effects on the cardiac conduction system through CB1 receptors.

Questions still open

Is cannabis-induced cardiac conduction disease more common than recognized? Does the mechanism involve CB1 receptor effects on conduction tissue, microvascular arteritis, or both? Would cessation eventually restore normal conduction?

Common questions

Did the heart block go away when cannabis was stopped?

The arrhythmia did not completely resolve at the three-month follow-up, and a permanent pacemaker was required.

How does cannabis cause heart block?

The mechanism is not fully understood. The conventional explanation involves increased vagal tone, but the prolonged HV interval in this case suggests possible direct toxic effects on the cardiac conduction system through CB1 receptors or cannabis-related microvascular damage.

Read the original research

Chronic Marijuana Consumption Leading to High-Grade Atrioventricular Block in a Young Male.

Cureus, 13(7), e16202

View on PubMed ↗Publisher’s paper ↗

Citation

Malviya, Amit; Khan, Shakeel A; Gupta, Anunay; Mishra, Animesh. (2021). Chronic Marijuana Consumption Leading to High-Grade Atrioventricular Block in a Young Male.. Cureus, 13(7), e16202. https://doi.org/10.7759/cureus.16202