CARDIAC TROPONIN-I AS AN EARLY MARKER OF MYOCARDIAL DAMAGE AFTER CORONARY-BYPASS SURGERY

Study objective: To evaluate the performance of cardiac specific marke rs, cardiac troponin I (cTnI) and CK-MB by mass assay (CK-MB mass), fo r the early diagnosis of myocardial ischemia and/or infarction after c oronary bypass surgery. Methods: Prospective clinical, electrocardiogr apic and biologic follow-up of 117 patients undergoing isolated coroll ary surgery with the use of intermittent anterograde normothermic blue d cardioplegia. Blood samples for biochemical analysis were drawn befo re surgery (T-0) and at 2 (T-1), 6 (T-2), 10 (T-3) and 20 h (T-4) afte r aortic cross-clamp release. Without knowledge of the biochemical dat a, patients were classified according to the electrocardiographic evol ution into two groups: group I, uneventful recovery and group 2. evide nce of ischemia/infarction based on continuous ST-T segment monitoring and 12-lead EGG. Results: No patients had abnormal markers at T-0. At T-1, although both markers were elevated, no difference was noted bet ween the two groups. At T-2 h after surgery, cTnl and CK-MB mass level s were significantly higher in group 2 than in group 1 (median = 17 mu g/l Interquartile Range (IR): 14.7-27.3 vs. 3.1 mu g/l, IR 1.9-5.3 fo r cTnI and median 42.5 mu g/l, IR: 27.1-95.7 vs. 13.6 mu g/l, IR: 9.5- 18.5 for CK-MB mass). A receiver operating characteristic (ROC) curve analysis shows that a cTnI value of. 13.1 mu g/l has 100% specificity and 90% sensitivity to separate both groups, Whereas a value of 33.2 m u g/l for CEC-MB mass has a specificity of 100% and a sensitivity of 7 3%. At T-3 and T-4, the same difference was noted between the groups. cTnl values in all six patients with a Q-wave infarction were greater than or equal to 20 ng/l, whereas only one of five patients with prolo nged ischemia bad cTnI level > 20 ng/ml. Conclusion: As soon as 6 h po stoperatively, cTnI and CK-MB by mass assay were able to separate thos e patients with an uneventful recovery from those with significant isc hemia. This is particularly useful in frequent cases when the ECG is d ifficult to interpret. (C) 1998 Elsevier Science B.V. All rights reser ved.