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), isc hemic preconditioning (IP), and hemodynamic function in coronary artery byp ass 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 is chemia followed by 3-min reperfusion before cross-clamping. Measurement and results: FR content in coronary sinus blood was measured di rectly using alpha -phenyl-N-tert-butylnitrone-electron spin-trapped spectr oscopy. A. small amount of FRs was generated after the IP protocol (5.6% ab ove the baseline) but not in control subjects. A larger amount was generate d 10 min after declamping in both groups (8.4% in IP protocol and 7.7% in c ontrol 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 ind ex (LVSWI) at 1 h and 6 h after declamping (r = -0.71 and - 0.59, respectiv ely) in the control subjects but not in the IP group. There was a significa nt positive correlation between FR generation after the IP protocol and car diac 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 grou p but not in the control subjects, Conclusion: FR generation after the operation correlates with ventricular f unctional depression in CABG patients. IP protects the stunning heart but d oes 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.