High level of cholesterol increases coronary vasomotor tone during exercise

Background Coronary vasomotor tone plays an important role in the regulatio n of myocardial perfusion and influences ischemic threshold significantly, Endothelial dysfunction occurs in the presence of coronary risk factors and is closely linked to the development of atherosclerosis affecting myocardi al perfusion and decreasing ischemic threshold, Objective To study the effect of hypercholesterolemia on coronary vasomotor tone in normal and stenotic coronary arteries at rest and during exercise. Patients and methods In total 48 patients were included in the present anal ysis. Patients were divided into two groups according to the actual levels of serum cholesterol: 18 patients had normal (mean 181 +/- 28 mg%; group 1) and 30 had elevated (mean 263 +/- 46 mg%; group 2) levels of serum cholest erol according to the 4S criteria with a cutoff level of 213 mg% (5.5 mmol/ l), Coronary vasomotor tone at rest and during supine bicycle exercise was calculated by dividing mean aortic pressure by radius of coronary vessel ob tained using biplanar quantitative coronary angiography, A normal as well a s a stenotic vessel segment in each patient were studied. Results Normal vessel segments in patients with normal levels of cholestero l (group 1) exhibited no exercise-induced change in coronary vascular tone (+3%, NS), whereas a significant increase in tone (+24%, P < 0.01 versus re st) occurred in those with high levels of cholesterol (group 2), In contras t, stenotic segments in members of both groups exhibited an increase in vas cular tone irrespective of the actual level of serum cholesterol. Conclusions Hypercholesterolemia causes a pathologic increase in coronary v asomotor tone of angiographically normal vessel segments during exercise. A similar pathologic response occurs in stenotic arteries, but this is indep endent of the actual level of serum cholesterol. These findings suggest tha t hypercholesterolemia influences vasomotor tone of the nonstenosed coronar y arteries in patients with coronary artery disease probably through the oc currence of endothelial dysfunction. Coron Artery Dis 11:459-466 (C) 2000 L ippincott Williams & Wilkins.