Plasma Troponins as Markers of Myocardial Damage during Cardiac Surgery with Extracorporeal Circulation

All types of cardiac surgery involve considerable injury to the myocardium. However, it is difficult to differentiate, in the immediate post-operative state, between ischemic alterations associated with the cardiac surgery itself and the pathological alterations of a peri-operative myocardial infarction. The diagnosis of damaged myocardium, classically performed with the enzymatic markers creatine kinase (CK) and its muscle fraction (CK-MB), has become more precise with the option of measuring cardiac troponins T and I. We measured these markers in 58 patients undergoing elective cardiac surgery with extra-corporeal circulation (ECC). The patients included 37 cases undergoing valve surgery, 14 for coronary revascularization, 6 for mixed procedures, and 1 for closure of an inter-atrial communication. The markers were measured in plasma at baseline (at anesthesia initiation), 5 min post-ECC commencement, following aorta de-clamping, during the surgical closure, and 6, 18 and 42 hrs after surgery. All the markers were increased significantly relative to the baseline values. Troponin I, CK and CK-MB values peaked between 6 and 18 hrs after surgery, troponin T between 18 and 42 hrs, and myoglobin at the surgical closure. The values of all markers were higher in patients undergoing coronary surgery compared to those in patients undergoing valve surgery. In the evaluation of myocardial damage after surgery, the measurement of classical markers such as CK and myoglobin remain valid, but other markers such as troponins provide significant additional diagnostic benefit and, thus, need to be included in the routine biochemical measurements for monitoring myocardial damage associated with the surgical procedure.