In their recent review, Thomas et al provide a concise overview of the cardiovascular effects of marijuana smoking. In fact, marijuana may acutely affect the circulatory system triggering cardiovascular events. Most published reports have focused on incidents of acute coronary syndromes, acute cerebrovascular and peripheral vascular events, and more rarely, ischemia-induced ventricular arrhythmias. However, an increasing number of case reports indicate an association between cannabis use and atrial fibrillation (AF). In a systematic review published in 2008, we analyzed 6 reported cases. In all instances AF was of recent onset occurring shortly after marijuana smoking in young subjects. No patient had a structural heart disease and only 1 had a precipitating factor (hypertension), and all patients had a favorable outcome with no recurrence after cessation of marijuana smoking. Since 2008, we have come across 2 cases of marijuana-associated paroxysmal AF in our center, both cases in young patients without any co-morbidities. Moreover, a retrospective 6-year period analysis of young patients (defined as aged ≤45 years) with “lone” AF admitted to City Hospital, Birmingham, UK showed that in 3 of 88 cases marijuana was the precipitating factor. One of these patients had further paroxysms of the arrhythmia due to continuing use of cannabis.

Of note, adrenergic stimulation and disturbances in atrial coronary or microvascular flow associated with marijuana smoking may facilitate AF development and perpetuation possibly because of increased pulmonary vein ectopy, enhanced atrial electrical remodeling, and increased dispersion of refractoriness.

It should also be stressed that although this adverse event seems to be quite “benign” in young healthy subjects, it is apparently more “malignant” in older patients having other risk factors for thromboembolism. The exact incidence of AF related to marijuana smoking is difficult to be estimated. Given the euphoric and neuropsychological effects of marijuana that may alter or cover palpitations or other symptoms suggestive of AF, this issue becomes more complicated. It should also be borne in mind that due to social or legal reasons, most users of illicit drugs avoid seeking medical attention. In addition, many short episodes of AF may pass unnoticed. Taking into consideration all these notions, it could be reasonable to conclude that the burden of the problem is possibly underestimated.