NEW YORK (Reuters Health) – Long-term treatment of idiopathic dilated cardiomyopathy (IDC) with the beta-blocker carvedilol increases coronary perfusion and function in patients with idiopathic dilated cardiomyopathy, Italian investigators report in the July issue of Heart. As a result, the drug appears to improve coronary microvascular function in these patients.

Lead author Dr. Danilo Neglia, from the CNR Institute of Clinical Physiology in Pisa, and colleagues conducted a double-blind trial of 16 patients with IDC, randomly assigned to carvedilol or placebo for 6 months. Carvedilol dosage was increased from a baseline dose of 6.25 mg twice daily up to a maximum of 25 mg twice daily.

The two groups were similar at baseline. After 6 months, six patients in the carvedilol group and four in the placebo group had improved in New York Heart Association functional class.

Carvedilol treatment was associated with significant decreases in heart rate and rate pressure product, at rest and during exercise, along with significant increases in submaximal exercise capacity.

Positron emission tomography imaging was performed to measure specific microvascular blood flow at rest and during pharmacological vasodilation by IV dipyridamole.

PET imaging showed that the beta blocker increased dipyridamole-induced myocardial blood flow and significantly increased coronary flow reserve. After correction for rate pulse pressure, the investigators observed that carvedilol led to significant increases in regional myocardial blood flow at rest. Stress-induced regional perfusion defects also decreased after carvedilol treatment.

"Increased myocardial blood flow reserve may well be one of the mechanisms of the observed increase in exercise tolerance in patients treated with carvedilol," Dr. Neglia’s team suggests.

They conclude: "In addition to (carvedilol’s) favorable effect on coronary microvascular function, it also improves myocardial-microvascular interplay."

Subjects in the placebo group did not realize any benefits on PET regional myocardial blood flow, coronary flu, exercise tolerance or hemodynamic variables.