Electronic Nicotine Delivery Systems and Cardiovascular Health: A Narrative Review of E-Cigarettes, Heated Tobacco Products, and the Challenge of Disentangling Risk.

Electronic nicotine delivery systems (ENDS), encompassing e-cigarettes, pod devices, and heated tobacco products (HTPs), have attained considerable global prevalence in recent years. While the cardiovascular consequences of conventional tobacco smoking are well characterized, the corresponding risks associated with ENDS remain incompletely understood. This review synthesizes the available evidence across device categories, drawing upon prospective cohort studies, randomized controlled trials (RCTs) of acute physiological effects, and experimental mechanistic research. Current evidence does not allow reliable quantification of cardiovascular risk attributable specifically to ENDS, independent of prior smoking, nor does it support the conclusion that these products are cardiovascularly safe. Dual use is associated with the highest observed risk, though this likely reflects both continued smoking exposure and differences in underlying user characteristics and should not be assumed to confer harm reduction. Direct ENDS versus cigarette comparisons are non-significant and of very low certainty; apparent benefit may reflect smoking cessation rather than a protective effect of ENDS per se. A main evidence gap is the absence of long-duration cohort data among individuals who have never smoked.