Increased vulnerability to atrial and ventricular arrhythmias caused by different types of inhaled tobacco or marijuana products

BACKGROUND The emergence of a plethora of new tobacco prod-ucts marketed as being less harmful than smoking, such as elec-tronic cigarettes and heated tobacco products, and the increased popularity of recreational marijuana have raised concerns about the potential cardiovascular risk associated with their use.OBJECTIVE The purpose of this study was to investigate whether the use of novel tobacco products or marijuana can cause the devel-opment of proarrhythmic substrate and eventually lead to arrhyth-mias. METHODS Rats were exposed to smoke from tobacco, marijuana, or cannabinoid-depleted marijuana, to aerosol from electronic ciga-rettes or heated tobacco products, or to clean air once per day for 8 weeks, following by assays for blood pressure, cardiac function, ex vivo electrophysiology, and histochemistry.RESULTS The rats exposed to tobacco or marijuana products ex-hibited progressively increased systolic blood pressure, decreased cardiac systolic function with chamber dilation, and reduced overall heart rate variability, relative to the clean air negative control group. Atrial fibrillation and ventricular tachycardia testing by ex vivo optical mapping revealed a significantly higher susceptibility to each, with a shortened effective refractory period and prolonged calcium transient duration. Histological analysis indicated that in all exposure conditions except for air, exposure to smoke or aerosol from tobacco or marijuana products caused severe fibrosis with decreased microvessel density and higher level of sympathetic nerve innervation.CONCLUSION These pathophysiological results indicate that to-bacco and marijuana products can induce arrhythmogenic sub-strates involved in cardiac electrical, structural, and neural remodeling, facilitating the development of arrhythmias.