Neutrophil Degranulation Related to the Reperfusion of Ischemic Human Heart During Cardiopulmonary Bypass

Activation of polymorphonuclear neutrophils (PMNs) during cardiopulmonary bypass (CPB) is a well-known phenomenon. This study aimed to determine if activated PMNs are sequestered and degranulated within the myocardium at reperfusion in patients undergoing coronary artery bypass grafting (CABG). Nineteen patients undergoing elective CABG were included in a prospective randomized study. Blood samples were obtained simultaneously from the radial artery (RA) and the coronary sinus (CS) at the following times: TO (5 min after onset of CPB), T1 (2 min after aortic unclamping), and T2 (10 min after aortic unclamping). Neutrophil function was evaluated by PMN count and by elastase and lactoferrin concentrations. All patients survived. Neutrophils increased significantly from TO to Tl and T2 in both RA and CS (p < 0.001 between TO and Tl or T2). Pre-ischemia and reperfusion were associated with a significantly lower neutrophil count in CS compared with RA blood (p < 0.001), suggesting that PMNs were trapped within the myocardium at the onset of the CPB. Elastase and lactoferrin concentrations increased significantly from TO to T1 and from T1 to T2 for each site, with greater concentrations (p < 0.001) in the CS compared with the RA, suggesting that activated neutrophils released their granular content into the plasma milieu only after reperfusion of the ischemic heart. This study establishes that neutrophil sequestration seems to be secondary to PMN activation by CPB but that the ischemia-reperfusion sequence induces specific degranulation of the PMNs trapped within the ischemic myocardium.