The effect of carvedilol therapy on coronary flow reserve in patients with idiopathic dilated cardiomyopathy

OBJECTIVES
We evaluated the effect of carvedilol, a nonselective beta-blocker with vasodilating action, on coronary flow reserve (CFR) in patients with idiopathic dilated cardiomyopathy (IDC).

STUDY DESIGN
Twenty-four patients (17 males, 7 females; mean age 57±11 years) with IDC were consecutively enrolled. After obtaining clinical and hemodynamic stabilization, transthoracic echocardiography was performed including CFR measurement and carvedilol therapy was initiated with 3.125 mg twice daily and titrated to a target dose of 25 mg twice daily. Twenty-three patients reached the target dose in a mean of 11±3 weeks. The mean duration of carvedilol therapy was 19±3 weeks, after which echocardiography was repeated and findings were recorded at baseline and after dipyridamole infusion. Clinical and echocardiographic findings were compared with those of 23 age- and sex-matched patients (13 males, 10 females; mean age 55±4 years) with atypical chest pain.

RESULTS
Compared to the control group, left ventricular end-diastolic and end-systolic volumes, left ventricular mass index, and isovolumic relaxation time were significantly higher and ejection fraction was significantly lower in the IDC group. Before carvedilol therapy, patients with IDC had a significantly higher baseline diastolic peak flow velocity (DPFV) and a significantly lower CFR; however, hyperemic DPFV was similar in the two groups. After carvedilol therapy, left ventricular end-systolic volume decreased significantly and ejection fraction increased significantly. Decreases in baseline DPFV and hyperemic DPFV were slight and there was no improvement in CFR. Even after elimination of the confounding effect of ratepressure product using analysis of covariance, pre- and post-treatment CFR remained similar.

CONCLUSION
Carvedilol therapy does not improve coronary microvascular functions in patients with IDC.