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: Observational 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 (T0) 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 lipid 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 to the functional ability of the heart.

Figure 1

Relation between myocardial total soluble glutathione content and heart function (LVEF). •, basal measurement (r = 0.909, p < 0.001); ∘, immediately after cross clamp removal (r = 0.603, p < 0.02).

Figure 2

Relation between coronary plasma glutathione redox ratio and heart function (LVEF): (A) before aortic cross clamping (r = 0.674, p < 0.01); (B) immediately after cross clamp removal (r = 0.714, p < 0.01); (C) 15 minutes after unclamping (r = 0.645, p < 0.01); (D) 30 minutes after unclamping (r = 0.702, p < 0.01).