Acute Effects of Smoking and Vaping on Markers of Vascular Function via Quantitative MRI

BACKGROUND: E-cigarettes contribute to endothelial dysfunction, a known cause of systemic atherosclerotic disease that cannot be adequately characterized by a single physiological parameter measured at a single vascular bed. PURPOSE/HYPOTHESIS: Quantify and compare acute effects of smoking or vaping with tobacco cigarettes (t-cigs), nicotinized e-cigarettes (e-cigs⁺), non-nicotinized e-cigarettes (e-cigs⁻) on the vascular system via quantitative MRI. STUDY TYPE: Prospective. SUBJECTS: Forty one smokers/vapers (mean age 29.8 ± 7.6 years), 17 non-smokers/non-vapers (mean age 26.5 ± 3.9 years). FIELD STRENGTH/SEQUENCE: 3 T/oximetry, blood flow velocimetry. ASSESSMENT: Smokers/vapers were scanned pre- and post- three challenges (ecig⁺, ecig, tcig). Each challenge was on a separate day. Blood flow velocity waveform in the femoral artery was measured at rest and in response to cuff occlusion, yielding parameters characterizing hyperemia (arterial peak velocity, time to peak, time of forward flow (TFF, duration of monophasic forward flow), hyperemic index, peripheral flow reserve, (PFR, peak over baseline velocity)). The dynamics of venous oxygen saturation (SvO₂) in the superficial femoral vein were quantified in terms of washout time of oxygen-depleted blood, upslope (rate of resaturation), and overshoot (peak SvO₂). Aortic pulse wave velocity was evaluated. Cerebrovascular reactivity and cerebral metabolic rate of oxygen consumption were assessed at the superior sagittal sinus. Neurovascular compliance was assessed at the common carotid arteries. STATISTICAL TESTS: Paired t-tests, Wilcoxon rank sum tests, linear mixed-effects models, Bonferonni corrections. p < 0.05 indicated statistical significance. RESULTS: At the femoral vein and artery, across users, post-challenge, the following decreased significantly: baseline SvO₂ (e-cig⁺: -12%; e-cig⁻: -14%; t-cig: -9%); baseline velocity (e-cig⁺: -23%; e-cig⁻: -22%; t-cig: -18%); TFF (e-cig⁺: -17%; e-cig⁻: -12%). The following significantly increased: upslope (e-cig⁺: +22%; e-cig⁻: +23%; t-cig: +19%); overshoot (e-cig⁺: +19%; e-cig⁻: +23%); PFR (e-cig⁻: +32%; t-cig: +31%). Accounting for user type, the mixed model showed TFF to decrease significantly post-challenge for all interventions: -15, -17, -23% for smokers, vapers, and dual users. DATA CONCLUSION: e-cig⁺, e-cig⁻, t-cig exposure resulted in strong, significant acute effects on vascular function markers. EVIDENCE LEVEL: 1. STAGE OF TECHNICAL EFFICACY: Stage 1.