OBJECTIVE To determine whether increased plasma concentrations of endothelin-1 (ET-1) and big endothelin (BET) play a role in the regulation of coronary circulation in patients with idiopathic dilated cardiomyopathy (IDCM).

SETTING Tertiary referral centre for cardiac diseases.

PATIENTS Fourteen patients (eight male/six female; mean (SD) age 59 (9) years) with IDCM (ejection fraction 36 (9)%) and five normotensive subjects (two male/three female; age 52 (7) years) serving as controls were studied.

RESULTS In the aorta, mean (SD) concentrations of ET-1 (IDCM 0.76 (0.25) v controls 0.31 (0.06) fmol/ml; p = 0.002) and BET (IDCM 3.58 (1.06) vcontrols 2.11 (0.58) fmol/ml; p = 0.014) were increased in patients with IDCM. Aortic ET-1 concentrations correlated positively with NYHA class (r = 0.731; p < 0.001), myocardial oxygen consumption (r = 0.749; p < 0.001), and coronary blood flow (r = 0.645; p = 0.003), but inversely with coronary sinus oxygen content (r = −0.633; p = 0.004), which was significantly decreased in IDCM patients (IDCM 4.68 (1.05)v controls 6.70 (1.06) vol%; p = 0.003).

CONCLUSIONS The coronary circulation in patients with IDCM is exposed to an increased endothelin load. ET-1 concentrations correlate with functional deterioration. A decrease of the coronary sinus content of oxygen suggests a mismatch between coronary blood flow and metabolic demand. Thus, ET-1 might be a marker of a disequilibrium between myocardial oxygen demand and coronary blood flow in IDCM.