Effect of myocardial damage sustained during coronary artery bypass and detected by qualitative troponin T on functional recovery of hibernating myocardium

Abstract

Despite modern intraoperative myocardial protection and improvements in surgical techniques, some degree of myocardial damage occurs during coronary artery bypass graft surgery (CABG). Recently, cardiac troponin T (TnT) is used widely to detect myocardial damage in our country. The aim of this study is to determine the effect of myocardial damage detected by qualitative cardiac TnT during CABG, on functional recovery of the hibernating myocardium. Forty-one cases with coronary artery disease, left ventricular dysfunction and hibernating myocardium detected by dobutamine stress echocardiography (DSE) were included in this study. Qualitative TnT and serial CK-MB measurements were made after CABG. Repeat echocardiography was performed at the third month after CABG and left ventricular function and functional recovery was evaluated. The functional recovery of the 19 TnT(+) and 22 TnT (-) cases were compared. Results: The parameters of TnT (+) and TnT(-) groups were listed below. The mean number of preoperative DSE (+) segment was 4,16 ± 1,43 and 3,68 ± 1,25. (NS) in TnT (+) and TnT(-) groups, respectively. The mean preoperative ejection fraction (EF) was 43 ± 11 % and 44 ± 9 % (NS), the mean number of impaired segment was 3,37 ± 1,07 and 3,13 ± 1,25 (NS), rate of impaired segments 83 ± 14 % and 85 ± 16 % (NS), peak postoperative CK-MB value 67 ± 39 U and 44 ± 23 U (p<0.05), and the mean postoperative EF was 49 ± 8 % and 51 ± 11 % (NS) in TnT (+) and TnT (-) groups respectively. There were no statistically significant differences between two groups except the CK-MB value. In the TnT (+) 3 cases, CK-MB values elevated more three times than normal value. There was also no change in preoperative and postoperative EF values in these cases. CK-MB values of TnT (+) group were found to be significantly elevated. There was no statistically significant difference between 2 groups in baseline preoperative values, postoperative improvement of hibernating segments, and global left ventricular function. Recovery of left ventricular function and hibernating segments were significantly depressed in 3 cases whom CK-MB values elevated obviously. Conclusions: Minor myocardial damage detected by qualitative TnT did not effect significantly recovery of hibernating myocardium in this study. Serious myocardial damage probably did not occur in the qualitative TnT (+) cases. Significantly increased quantitative TnT or CK-MB levels are related to extensive myocardial damage. Comparing quantibative studies to qualitative TnT evaluation will prove more information in this area.