Relation between left ventricular function and oxidative stress in patients undergoing bypass surgery

Abstract

Objective - To determine whether preoperative left ventricular ejection fraction (LVEF) is related to the degree of myocardial oxidative stress during bypass surgery in man. Design - Observation study. Setting - Tertiary care centre. Patients and interventions -31 patients (LVEF range was 20% to 68%) undergoing elective coronary bypass surgery with blood cardioplegic reperfusion were studied. Arterial and coronary sinus blood was collected before aortic cross clamping (T1) and at 0 (T1), 15 (T2), and 30 (T3) minutes after unclamping. Transmural left ventricular biopsies were also obtained from 15 patients at T0 and at T1. Main outcome measures - Glutathione and adenine nucleotides were measured in myocardial biopsies, while coronary sinus-artery differences for glutathione, nucleotides, and products of lipids peroxidation were calculated from blood specimens. Creatine kinase (myocardial band; CK-MB) was measured in plasma at four and 12 hours after operation. Results - Myocardial glutathione and adenine nucleotides were correlated (p<0.02) with preoperative LVEF both at T0 (r = 0.909 and 0.672) and T1 (r = 0.603 and 0.605). Oxidised glutathione released from the heart during reperfusion was inversely correlated with LVEF (r = 0.448, -0.466, and -0461 at T1, T2, and t3, p<0.01), while reduced glutathione (r = 0.519 and 0.640 at T1 and T2) and glutathione redox ratio (r = 0.647, 0.714, 0.645, and 0.702 at T0, T1, T2, and T3) showed a direct correlation (p<0.01). Lipid peroxidation at T1 was negatively related to LVEF (r = 0.492). CK-MB was also negatively related to LVEF (r = 0.440 at 4 h and -0.462 at 12 h). Conclusions - The capacity to counterbalance oxidative burst following ischaemia and reperfusion appears to be related o the functional ability of the heart.