Effect of ischemic preconditioning on myocardial protection in coronary artery bypass graft patients - Can the free radicals act as a trigger for ischemic preconditioning?

Objective: To investigate the interrelationship of free radicals (FRs), ischemic preconditioning (IP), and hemodynamic function in coronary artery bypass graft (CABG) patients. Design: Prospective, randomized, and controlled clinical study. Patients: Forty CABG patients were randomized into an IP group (n = 20) and a control group (n = 20). Intervention: The IP group was preconditioned with two cycles of two-min ischemia followed by 3-min reperfusion before cross-clamping. Measurement and results: FR content in coronary sinus blood was measured directly using alpha -phenyl-N-tert-butylnitrone-electron spin-trapped spectroscopy. A. small amount of FRs was generated after the IP protocol (5.6% above the baseline) but not in control subjects. A larger amount was generated 10 min after declamping in both groups (8.4% in IP protocol and 7.7% in control subjects). Hemodynamic function recovered better in the IP group at 1 h and 6 h after declamping. There was a significant negative correlation between FR generation after declamping and left ventricular stroke work index (LVSWI) at 1 h and 6 h after declamping (r = -0.71 and - 0.59, respectively) in the control subjects but not in the IP group. There was a significant positive correlation between FR generation after the IP protocol and cardiac index at 1 h and 6 h (r = 0.50 and 0.61, respectively) and LVSWI at 1 h and 6 h (r = 0.56 and 0.54, respectively) after declamping in the IP group but not in the control subjects, Conclusion: FR generation after the operation correlates with ventricular functional depression in CABG patients. IP protects the stunning heart but does not alter FR generation. The association of better hemodynamic recovery after CABG with FR generation during the IP period suggests that FRs might act as one of the triggers for IP.