The aim of the study was to assess the left ventricular (LV) diastolic filling response to the cold pressor test in asymptomatic or mildly symptomatic patients with nonobstructive hypertrophic cardiomyopathy (HC) before and after verapamil therapy. The cold pressor test-induced alterations in LV filling pattern were additionally compared between HC patients and healthy control subjects. The cold pressor test, producing alpha- and beta-adrenergic stimulation, differentiates paradoxical coronary vasoconstriction due to endothelial dysfunction from the normal endothelium-dependent vasodilation. Such opposite coronary vasomotion at cold pressor test may be reflected by different responses of LV diastolic filling to the cold pressor test. Doppler echocardiography was performed in 10 asymptomatic or mildly symptomatic patients with nonobstructive HC as well as in 10 age- and sex-matched healthy subjects before and immediately after the cold pressor test. In HC patients before verapamil therapy, the cold pressor test induced a significant decrease in LV early filling parameters, contrary to healthy subjects, in whom the cold pressor test improved early filling [changes in early diastolic LV velocity -6.2 +/- 7.3 (-11.4 to -0.98) vs. 7.5 +/- 8.9 (1.13-13.86) cm/s, P = 0.0014, and changes in its acceleration rate -136 +/- 119 (-221 to -51) vs. 252 +/- 181 (122-381) cm/s2, P = 0.0001, respectively]. Verapamil therapy restored the normal pattern of the LV early filling response to the cold pressor test [changes in early diastolic LV velocity -6.2 +/- 7.3 (-11.4 to -0.98) vs. 5.3 +/- 3.4 (2.86 to 7.73) cm/s, P = 0.0003, and changes in its acceleration rate -136 +/- 119 (-221 to -51) vs. 328 +/- 185 (196 to 460) cm/s2, P = 0.0001, respectively]. Verapamil normalizes the LV early filling response to the cold pressor test in asymptomatic or mildly symptomatic patents with HC.