Acute Effect of Hookah Smoking on the Human Coronary Microcirculation

Abstract

Hookah (water pipe) smoking is a major new understudied epidemic affecting youth. Because burning charcoal is used to heat the tobacco product, hookah smoke delivers not only nicotine but also large amounts of charcoal combustion products, including carbon-rich nanoparticles that constitute putative coronary vasoconstrictor stimuli and carbon monoxide, a known coronary vasodilator. We used myocardial contrast echocardiography perfusion imaging with intravenous lipid shelled microbubbles in young adult hookah smokers to determine the net effect of smoking hookah on myocardial blood flow. In 9hookah smokers (age 27 ± 5years, mean ± SD), we measured myocardial blood flow velocity (β), myocardial blood volume (A), myocardial blood flow (A× β) as well as myocardial oxygen consumption (MVO2) before and immediately after 30minutes of ad lib hookah smoking. Myocardial blood flow did not decrease with hookah smoking but rather increased acutely (88 ± 10 to 120 ± 19 a.u./s, mean ± SE, p=0.02), matching a mild increase in MVO2 (6.5 ± 0.3 to 7.6 ± 0.4ml·minute(-1), p <0.001). This was manifested primarily by increased myocardial blood flow velocity (0.7 ± 0.1 to 0.9 ± 0.1second(-1), p=0.01) with unchanged myocardial blood volume (133 ± 7 to 137 ± 7 a.u., p=ns), the same pattern of coronary microvascular response seen with a low-dose β-adrenergic agonist. Indeed, with hookah, the increased MVO2 was accompanied by decreased heart rate variability, an indirect index of adrenergic overactivity, and eliminated by β-adrenergic blockade (i.v. propranolol). In conclusion, nanoparticle-enriched hookah smoke either is not an acute coronary vasoconstrictor stimulus or its vasoconstrictor effect is too weak to overcome the physiologic dilation of coronary microvessels matching mild cardiac β-adrenergic stimulation.