Unspecific elevation of plasma troponin-T and CK-MB after coronary surgery

• Objective - Biochemical markers of myocardial injury are frequently elevated after cardiac surgery. It is generally accepted that release unrelated to permanent myocardial damage explains a proportion of these elevations. However, little is known about the magnitude and temporal characteristics of this diagnostic noise. One way to address this issue would be to study a group without permanent myocardial injury. Design - The unique release kinetics of troponin-T (permanent myocardial injury causes a sustained release of structurally bound troponin) were used to identify patients with no or minimal permanent myocardial injury. Blood was sampled from patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) before surgery, 3 and 8 h after unclamping the aorta, and each morning until postoperative day 4, for analysis of enzymes and troponin-T. From 302 consecutive patients a subgroup was identified that fulfilled the following criteria: (a) normalized troponin-T levels =postoperative day 4, (b) no ECG changes indicating myocardial injury. Results - Seventy-seven patients fulfilled the criteria above and in this subgroup troponin-T (2.08 ▒ 1.42 ╡g/ 1, range 0.35-8.99 ╡g/l) peaked at the 3 h recording and creatine kinase monobasic (CK-MB) (28.6 ▒ 11.3 ╡g/l, range 11.9-86.0 ╡g/l) peaked at the 8 h recording after unclamping the aorta. Conclusion - Substantial early elevations of plasma CK-MB and troponin-T occurred in patients with no or minimal permanent myocardial injury after CABG. Unspecific release was most pronounced during the timeframe that is usually studied to evaluate myocardial protective strategies or to compare revascularization procedures.

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