Due to the pandemic we decided to terminate this project.

E-cigarettes deliver nicotine by creating an aerosol of ultrafine particles. Many questions remain about the size and composition and especially about the potential toxicity of these particles. Thus, a key unanswered question-and the research question proposed-is whether e-cigarette aerosol triggers the same acute impairment in coronary microvessel function as does conventional cigarette smoke, which delivers a very well-defined exposure to fine particles and many fold greater exposure to toxic (combustion) products including volatile organic compounds (such as acrolein) that have been implicated in the pathogenesis of tobacco-related coronary disease.

Because the effects of nicotine on the human coronary microcirculation remain incompletely defined-with multiple potential vasodilator and vasoconstrictor actions each of which may vary by dose-we will determine the comparative effects of conventional cigarette smoke against e-cigarette aerosol with no nicotine, with low-dose nicotine, and with high-dose nicotine.

Inclusion Criteria:

• Age 18-49
• Regular cigarette smoker defined as at least 1 pack year and ≥ 5/day
• E-cigarette smoker defined as ≥ 1/week in the last 6 months.

Exclusion Criteria:

• Sub-optimal echocardiography images as determined by the sonographer and/or investigators.
• History of cardiopulmonary (including asthma or use of inhalers),
• History of diabetes or dyslipidemia
• History of psychiatric illness
• Blood Pressure > 140/90
• Body Mass Index ≤ 18.5 or ≥ 30 kg•m2
• Evidence of any of the above by physical examination, Electrocardiogram (ECG) or echocardiogram
• Resting Heart Rate > 100 beats/min
• Cardiac rhythm disorder, specifically: rhythm other than sinus, Supraventricular Tachycardia (SVT), atrial fibrillation, ventricular tachycardia
• Use of prescription medication except oral contraceptive pills
• History of illicit drug use (self-stated)
• Pregnant
• Any other condition(s) deemed by the physician investigators that put subjects at risk for participating in the study