MRI-assessed Alterations in Cardiovascular Dynamics With Electronic Nicotine Delivery System Use in Young Adults

Rationale
Electronic Nicotine Delivery systems (ENDS) remain the most used tobacco product in young adults, with 26.3% of current users reporting daily use. Long-term ENDS use is associated with endothelial dysfunction, oxidative stress, and vascular remodeling and increased risk of cardiovascular disease from both inflammatory processes and activation of the sympathetic nervous system. Cardiovascular hemodynamics are hypothesized to be altered from pulmonary vascular remodeling and perfusion redistribution, similar to those observed in combustible cigarette users. We seek here to evaluate presence of these changes in young adults at-risk from long-term cumulative use.

Methods
Eight ENDS users (Vapers) aged 18-24, and five age-matched healthy controls (with no tobacco/vaping history) were recruited. Subjects completed symptom and use questionnaires, followed by pulmonary function tests (PFTs), and imaging on a 3T Signa Premier MRI system (GE HealthCare, IL). Cardiac flow was assessed using a time-resolved 3D phase-contrast MRI protocol with three-directional velocity encoding (4DFlow), with cardiac triggering. The field of view was set to cover the ascending aorta and the heart. Circular regions of interest on the ascending aorta (AA) and the pulmonary artery (PA) were used for measurement of diameter, flow, and wall shear stress using the CardiacApp on the TempusPixel platform (Tempus, IL). Flow measurements were normalized by lung volume at functional residual capacity (FRC) derived from chest CT imaging, and separately with an estimate of body surface area using the Du-Bois model, to account for body size differences. Unpaired t-tests were used to test for significance of differences between the groups.

Results
A summary of the demographics and findings are presented in the Table. PA flow (normalized by lung volume) was significantly lower in vapers (1.78±0.48 vs. 2.39±0.38 L/min/L in controls, p=0.04). Across both groups, absolute flow and diameter in the PA trended towards a 17% decrease, but did not reach statistical significance in this pilot study. AA diameter also trended towards a similar percent decrease, though not statistically significant, resulting in a matched PA/AA ratio between the two groups.

Conclusions
Compared to age-matched healthy controls, our pilot data suggests early alterations in cardiovascular hemodynamics in the pulmonary artery in young ENDS users. An expanded study population can help assess the risk factors associated with cardiovascular impact, and in conjunction with pulmonary structural and vascular analysis, can be used to model cardio-pulmonary interactions and progression with long-term use.