Coronary flow reserve is reduced in patients with
idiopathic dilated cardiomyopathy (DCM). We examined acute effects of intracoronary
enalaprilat on metabolic coronary vasodilation during pacing
tachycardia in patients. Coronary blood flow (Doppler guidewire) and diameter (quantitative angiography) were measured in seven patients with DCM and seven control subjects. In the DCM group, tachypacing increased coronary blood flow by 37 +/- 22% from the baseline before
enalaprilat and by 65 +/- 22% (p < 0.01 vs. before treatment) after
enalaprilat (0.5 microg/kg/min for 5 min, i.c.) at comparable double product. Pacing-induced dilation of the epicardial coronary artery also was greater after
enalaprilat (p < 0.05). Effects of
enalaprilat on coronary blood flow and diameter during pacing
tachycardia were abolished by pretreatment with intracoronary administration of the
nitric oxide (NO) synthesis inhibitor, N(G)-monomethyl-
L-arginine. These beneficial effects of
enalaprilat on large and small coronary vasodilation were not observed in control patients. Thus, intracoronary
enalaprilat acutely augmented dilator responses of the large and small coronary arteries to pacing
tachycardia in patients with DCM, and NO appeared to play an important role in mediating the effects of
enalaprilat. These favorable effects of
enalaprilat on the coronary circulation may be of clinical significance in patients with
heart failure due to nonischemic DCM. Further long-term studies of the effects of
angiotensin-converting enzyme inhibition on coronary vasodilation will be needed in this population.