VASODILATORY CAPACITY OF CORONARY RESISTANCE VESSELS IN DILATED CARDIOMYOPATHY

Both the endothelium-dependent and endothelium-independent vasodilator y responses of coronary resistance vessels were studied in patients wi th dilated cardiomyopathy (DCM). A 3F coronary Doppler catheter was pl aced in the proximal left anterior descending artery in 14 patients wi th DCM and in 10 patients with chest pain syndrome and a normal heart (control subjects). The ratio of maximum mean coronary blood flow velo city after intracoronary administration of the endothelium-independent vasodilator papaverine (10 mg) to resting mean coronary blood flow ve locity (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 acetylc holine (40 mu g) (Va/Vo) in 10 DCM patients was also diminished compar ed 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 e nd-diastolic pressure (r = -0.48, e < 0.05), left ventricular end-dias tolic 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 parame ters. These results indicate that impairment of the vasodilatory capac ity of coronary resistance vessels in DCM may be related to endothelia l dysfunction and to an extravascular factor resulting from left ventr icular dysfunction.