Effects of long-term treatment with carvedilol on myocardial blood flow in idiopathic dilated cardiomyopathy

Objective To assess whether chronic treatment with carvedilol is able to increase myocardial blood flow (MBF) and MBF reserve in idiopathic dilated cardiomyopathy (IDC). Study Design In a double-blind, placebo-controlled trial, 16 consecutive IDC patients were randomized to treatment with carvedilol up to 25 mg b.i.d (8 pts, 7 males, mean age 60iO9 years, mean LVEF 30iO%) or placebo (8 pts, 6 males, mean age 62iO9 years, mean LVEF 28iO6%, ns vs carvedilol group). Before and six months after treatment, regional MBF was measured at rest and after i.v. dipyridamole (0.56 mg/Kg in 4') by positron emission tomography and 13N-Ammonia. Exercise capacity was assessed as time duration in a maximal bicycle exercise stress test. Results Carvedilol induced a significant decrease in resting and maximal exercise heart rate and increase in exercise capacity. Absolute MBF values did not significantly change after carvedilol or placebo either at rest and during dipyridamole. In patients treated with carvedilol, dipyridamole MBF tended to improve after treatment and MBF reserve significantly increased (from 1.67iO0.63 to 2.58iO1.04, p0.001) while it remained unchanged in the placebo group (from 1.80iO0.84 to 1.77iO0.60, ns). Stress-induced regional perfusion defects decreased after carvedilol (from 38% to 15%). Conclusions Long-term treatment with carvedilol is able to significantly increase MBF reserve and to reduce the occurrence of stress induced perfusion defects suggesting a favourable effect of the drug on coronary microvascular function in patients with IDC.