Impaired Endothelium Independent Vasodilation in Nonobstructive Hypertrophic Cardiomyopathy

BACKGROUND: In patients with hypertrophic cardiomyopathy (HCM) an impaired microvascular function is reported not only in the hypertrophied septum but also in the nonhypertrophied left ventricular free wall as well as in forearm resistance vessels, thus suggesting a generalized alteration in vascular function. However, information on conduit artery involvement is still sparse and controversial. The aim of this study was to evaluate whether functional abnormalities are detectable in the arteries of HCM patients. METHODS: In a group of newly diagnosed, previously untreated, patients with nonobstructive HCM, conduit artery endothelium dependent and independent vasodilation (EDV and NEDV, respectively) were assessed with high resolution ultrasound by measuring respectively flow-mediated vasodilation and response to sublingual nitroglycerine of the brachial artery. Normotensive subjects free of cardiovascular disease and risk factors and untreated hypertensive patients with left ventricular hypertrophy were studied as control groups. RESULTS: Compared to normotensives, HCM patients showed significantly blunted NEDV (13 ± 6% vs. 23 ± 7%, P < 0.01), whereas EDV was not significantly different between the two groups (11 ± 4 for HCM vs. 13 ± 4% for normotensives, P = 0.25). In the hypertensive group, both NEDV and EDV were significantly decreased compared to normotensives (P = 0.01 and P < 0.01, respectively). CONCLUSIONS: Patients with HCM show a reduced vasodilator response of systemic conduit arteries to nitroglycerine, suggesting a remodeling of vascular wall or smooth muscle cell dysfunction.