Lipid peroxidation and cardiac troponin T release during routine cardiac surgery

Myocardial injury after cardiac surgery with cardiopulmonary bypass may be related to free oxygen radical-induced lipid peroxidation. The purpose of this study was to monitor perioperative changes of cardiac troponin t and malondialdehyde as an indicator of lipid peroxidation in patients who underwent routine cardiac operation and had no signs of perioperative myocardial infarction. Patients with thoracic surgery alone served as controls. We studied 20 patients with cardiopulmonary bypass (CPB) and 9 patients with other thoracic operations. Serum troponin t, malondialdehyde, myoglobin, creatine kinase (CK) including CK-MB isoenzyme levels were monitored before CPB, immediately after cessation of CPB, 20 and 44 h after CPB. Patients with signs of myocardial infarction before or up to 44 h after surgery were excluded. Of 20 patients with CBP, 18 patients showed a significant increase of troponin t and 16 patients had elevated malondialdehyde serum levels following CPB. Troponin t serum values were raised immediately after CPB to 0.60 +/- 0.12 microg/l and increased further to 0.90 +/- 0.17 microg/l after 44 h (p < 0.005, in comparison to preoperative: 0.08 +/- 0.02 microg/l). Patients undergoing the other thoracic operations showed neither any detectable troponin t serum values nor significant changes of serum malondialdehyde during the observed period. In the CPB group serum malondialdehyde peaked immediately after CPB to 98 +/- 9 nmol/g albumin (p < 0.005) and returned to preoperative levels (63 +/- 3 nmol/g albumin) within 20 h (60 +/- 3 nmol/g albumin). Individual maximal troponin t serum levels did not correlate with individual maximal serum malondialdehyde levels. The observed increase of troponin t levels had no influence on patients' outcome followed up for 18 months. The results demonstrate that troponin t and lipid peroxidation increase during uncomplicated cardiac surgery in patients without signs of myocardial infarction. Following uncomplicated cardiac surgery, a moderate increase of cardiac troponin t may not reflect severe cardiac injury.