PERIOPERATIVE PLASMA LEVELS OF CD63-POSITIVE EXOSOMES IN OLDER PATIENTS UNDERGOING FIRST-TIME CABG OR VALVE REPLACEMENT SURGERY: A PRELIMINARY COMPARISON TO CARDIAC TROPONIN I AND CREATINE KINASE-MB

Purpose. Blood biomarkers of myocardial viability that guide management in cardiac surgical patients are still lacking. To compare the perioperative levels of circulating CD63-positive exosomes (EXOs), smallest secreted nanovesicles with cardioprotective properties, and the biomarkers of myocardial injury in elderly patients undergoing different type of cardiac surgery with cardiopulmonary bypass (CPB). Methods. Blood samples were collected from 16 male older patients (65±9 years; NYHA II-III), undergoing valve replacement (VR; nonischemic; n=7) or first-time coronary-artery by-pass graft (CABG; ischemic; n=9) with CPB to measure plasma levels of EXOs 1) before initiation of CPB (T0), 2) at 3h after CPB (T1) and 3) at 3 days after the end of the operation (T2). Similarly, we measured the serum levels of cardiac Troponin I (cTnI) and Creatine Kinase-MB isoenzyme (CK-MB), biomarkers of myocardial injury. Plasma EXOs were isolated by serial ultracentrifugations and were quantified by Western blot. Results. At similar perioperative management, the exosomal profile is significantly different in VR and CABG patients. At T0, the levels of EXOs are higher in VR compared to CABG patients (P<0.01). Even if the cross-clamp time in VR is higher than CABG patients, EXOs levels do not change over time. In CABG patients, plasma EXOs are significantly increased by 20% at T1 and by 45% at T2 (P< 0.01). Conversely, the cTnI and CK-MB levels decline at T2 (P<0.05; r:0.645) after initial increase at T1 in CABG patients. Conclusions. Our preliminary results suggest that the prolonged rise of plasma EXOs levels is a potential innovative perioperative indicator of myocardial viability after weaning from CPB in older patients undergoing CABG. It is conceivable that high EXOs levels may protect other organs, including the heart.