CIRCULATING ENDOTHELIN IN PATIENTS UNDERGOING CORONARY-ARTERY BYPASS-GRAFTING

Increased synthesis of endothelin, (a powerful physiological vasoconstrictor), is a uniform response to endothelial injury and has been associated with myocardial ischemia and reperfusion. This study tests the hypothesis that coronary artery bypass grafting (CABG) affects endothelin plasma concentrations in various vascular beds. Twenty-four CABG patients were included in this study. Endothelin was determined in multiple plasma specimens obtained from superior vena cava, aortic root and coronary sinus (CS). Venous endothelin plasma concentrations collected in CABG patients before surgery were 1.16 +/- 0.18 pg/ml. They increased after sternotomy (1.71 +/- 0.12 pg/ml) and during (2.97 +/- 0.27 pg/ml) and after cardiopulmonary bypass (CPB, 2.72 +/- 0.21 pg/ml). There is no net release of endothelin from the coronary circulation before (aorta 2.26 +/- 0.13 pg/ml vs CS 2.44 +/- 0.17 pg/ml, not significant (n.s.), during (cardioplegia 2.55 +/- 0.17 pg/ml vs CS 2.45 +/- 0.15 pg/ml, n.s.), and after aortic cross-clamping (aorta 2.95 +/- 0.23 pg/ml vs coronary sinus 2.71 +/- 0.18 pg/ml, n.s.). Pulmonary endothelin clearance is preserved on partial bypass (aorta 2.26 +/- 0.13 pg/ml vs vena cava 2.86 +/- 0.18 pg/ml, P < 0.003), but remains inhibited even 10-30 min after release of the aortic cross-clamp (aorta 2.95 +/- 0.23 pg/ml vs vena cava 2.97 +/- 0.27 pg/ml, n.s.). Two out of 24 patients had severe myocardial ischemia. These patients showed particularly high endothelin concentrations. We conclude that (1) anesthesia and sternotomy and, to a greater extent, CPB increase endothelin concentrations, (2) the absence of pulmonary endothelin clearance after total bypass may indicate pulmonary endothelial dysfunction or damage, (3) there is no coronary net release of endothelin before, during and after aortic cross-clamping, and (4) severe myocardial ischemia may be associated with increased endothelin concentrations.