Acute Effect of Esmolol Intravenously on Coronary Microcirculation in Patients With Idiopathic Dilated Cardiomyopathy

Although coronary flow reserve (CFR) impairment was correlated with the prognosis of patients with idiopathic dilated cardiomyopathy (IDC) and microvascular ischemia was implicated in the progress of the disease, little is known about the effect of the established therapy with β blockers on coronary microcirculation. The purpose of this study was to assess the effect of β1 blockade on coronary blood flow and CFR in patients with IDC. Fourteen patients with IDC and 10 control subjects underwent time-averaged peak coronary flow velocity (APCFV) measurements (centimeters per second) in the proximal left anterior descending coronary artery at baseline and at maximal hyperemia before and after β1 blockade with intravenous esmolol. CFR was defined as APCFV at maximal hyperemia/APCFV at baseline. Although there were no significant differences in APCFV at baseline between patients with IDC and controls, patients with IDC had significantly lower APCFV at maximal hyperemia than controls (54.2 ± 12.0 vs 75.1 ± 18.6, p <0.05) and decreased CFR (2.39 ± 0.38 vs 3.50 ± 0.54, respectively, p <0.05). After β1 blockade, a significant decrease in APCFV at baseline (19.5 ± 3.7 vs 22.9 ± 5.0, p <0.05) and enhancement of APCFV at maximal hyperemia (59.5 ± 13.3 vs 54.2 ± 12.0, p <0.05) were observed in patients with IDC, but not in control subjects, leading to significant improvement in CFR (3.06 ± 0.40 vs 2.39 ± 0.38, p <0.05). In conclusion, patients with IDC had alterations in coronary blood flow and decreased CFR that improved after β1 blockade. These alterations in microvascular function, which are partially reversed by β blockade, may be 1 of the underlying mechanisms that contribute to the improved prognosis of patients with IDC under such therapy.