VASODILATORY CAPACITY OF CORONARY RESISTANCE VESSELS IN DILATED CARDIOMYOPATHY

Both the endothelium-dependent and endothelium-independent vasodilatory responses of coronary resistance vessels were studied in patients with dilated cardiomyopathy (DCM). A 3F coronary Doppler catheter was placed in the proximal left anterior descending artery in 14 patients with DCM and in 10 patients with chest pain syndrome and a normal heart (control subjects). The ratio of maximum mean coronary blood flow velocity after intracoronary administration of the endothelium-independent vasodilator papaverine (10 mg) to resting mean coronary blood flow velocity (Vp/Vo) in patients with DCM was diminished compared with that in control subjects (2.2 +/- 0.6 vs 4.1 +/- 0.9, p < 0.001). The ratio after administration of the endothelium-dependent vasodilator acetylcholine (40 mu g) (Va/Vo) in 10 DCM patients was also diminished compared with that in seven control subjects (1.3 +/- 0.5 vs 2.4 +/- 0.8, p < 0.01). In DCM patients, Vp/Vo was correlated with left ventricular end-diastolic pressure (r = -0.48, e < 0.05), left ventricular end-diastolic volume index (r = -0.68, p < 0.01), ejection fraction (r = 0.75, p < 0.01), and left ventricular end-diastolic wall stress (r = -0.73, p < 0.01). However, Va/Vo was not correlated with any of these parameters. These results indicate that impairment of the vasodilatory capacity of coronary resistance vessels in DCM may be related to endothelial dysfunction and to an extravascular factor resulting from left ventricular dysfunction.