Electronic cigarettes prolong ventricular repolarization in people who smoke tobacco cigarettes: implications for harm reduction.

Introduction:
This article reports a study that examines the effects of electronic cigarettes (ECs) on ventricular repolarization in people who smoke tobacco cigarettes (TCs) and compares them with the effects of tobacco cigarettes. The study aims to determine the relative risks of ECs and TCs as harm reduction strategies for smoking cessation. The study design and major points are summarized below:

* The study included 110 participants, divided into three cohorts: tobacco cigarette smokers, electronic cigarette users, and nonusers.
* Baseline ECG parameters and heart rate were compared among the three cohorts in supine and standing positions.
* Participants in the tobacco cigarette and electronic cigarette cohorts underwent a series of exposures on different session days in random order.
* The experimental protocol included blood draws for nicotine and cotinine levels and ECG recordings before and after each exposure.
* The ECG recordings were analyzed using commercially available software to identify the onset of the qRS complex, the peak of the T wave, and the end of the T wave.
* The Tp-e interval was measured as the difference between the peak of the T wave and the end of the T wave.
* Nicotine and cotinine plasma levels were measured before and after each intervention.
* The study found that acutely smoking a tobacco cigarette markedly and significantly increased all three parameters of ventricular repolarization in people who chronically smoked tobacco cigarettes.
* In contrast, in people who exclusively used electronic cigarettes, only one of the three parameters, the Tp-e-to-qT ratio, was prolonged, and the increase was significantly less than that seen in smokers acutely using an equivalent "dose" of a tobacco cigarette.
* however, the study also found that using an electronic cigarette compared with a tobacco cigarette acutely and significantly prolonged several metrics of ventricular repolarization, including Tp-e, Tp-e/qT, and Tp-e/qTc.
* Furthermore, in a subgroup analysis by sex, this adverse effect on repolarization was found only in male, not female, smokers.

Main message:
The study suggests that electronic cigarettes may not be a safer alternative to tobacco cigarettes regarding ventricular repolarization, especially in male smokers. Therefore, if used for smoking cessation, ECs should only be used in the short term since they too carry their own risks. The study highlights the need for further research on the relative risks and benefits of ECs and TCs as harm reduction strategies for smoking cessation.

Ruedisueli I, Lakhani K, Nguyen R, Gornbein J, Middlekauff hR. Electronic cigarettes prolong ventricular repolarization in people who smoke tobacco cigarettes: implications for harm reduction. american journal of physiology heart and circulatory physiology. 2023;324(6):h821-h832. doi:10.1152/ajpheart.00057.2023