Cannabis-Induced Third-Degree AV Block

Background Cannabis (marijuana) is the most widely consumed illicit drug in Europe. However, many are unaware of its potential cardiovascular side effects. Case Report A 19-year-old man presented to the emergency department with palpitations and presyncope after smoking cannabis. A third-degree atrioventricular block (complete heart block) was diagnosed. We believe cannabis exposure to have been the likely cause. Extensive work-up—including Borrelia and auto-immune serology, CT coronary angiography, magnetic resonance imaging, and electrophysiological study—was negative. The patient was initially treated with IV isoprenaline. Within one day, the bradycardia spontaneously resolved. The patient was advised to quit using cannabis. No further therapy was initiated. We discuss the clinical presentation, pathophysiology, and evidence from the literature linking cannabis exposure to bradycardia. Conclusion We describe a case of third-degree atrioventricular block after cannabis use. Emergency physicians should be aware of the potential cardiovascular side effects of this drug.