Cardiac Troponin T to evaluate myocardial protection via intermittent cold blood or continuous warm blood cardioplegia in coronary artery bypass grafting.

BACKGROUND

The aim of our study was to evaluate the efficacy of myocardial protection during coronary artery bypass grafting (CABG) in cold blood intermittent (CBIC) and warm continuous blood cardioplegia (WCBC). To assess myocardial necrosis, Troponin T, a structural protein belonging to the troponin complex, was measured. Troponin T is released in the blood stream 4 hours after myocardial damage, and it does not cross-react with the isomeric form of the skeletal muscle.

METHODS

Our study involved 20 consecutive patients, scheduled for isolated CABG. They were divided into two groups: the first group (10 patients; 8 m, 2 f) underwent surgery with the use of CBIC, the second group (10 patients; 9 m, 1 f) with WCBC. The serum levels of cardiac Troponin T (cTn-T) were all <0.2 microg/l before operation.

RESULTS

In the CBIC the mean cTn-T peaked on the 1st day after CABG, in the WCBC group the first peak occurred in the 2nd hour after arrival in the intensive care unit, and the second peak occurred on the 4th day postoperatively. The mean serum cTn-T was lower in the WCBC vs CBIC group from the 1st to the 5th day postoperatively, with a statistical difference on the 1st day (p<0.05). In the CBIC group either the cTn-T peak values (r=0.77; p<0.02) or area under the concentration curve of cTn-T release (r=0.85; p<0.004), were directly correlated with the aortic cross-clamping time. This was not demonstrated in the WCBC. CPK and CK-MB peaked in both groups 6 hours after arrival in the intensive care unit and on the 1st day postoperatively, with higher values at 6 hours in the WCBC group (p<0.05). The CK-MB/CPK ratio was significantly lower in the WCBC group at the six hours (p<0.05).

CONCLUSIONS

The results of this preliminary study suggest that fewer necrosis markers are released during CABG in the WCBC group; in the CBIC group the release of cTn-T whether measured by peak serum level or by area under the curve, shows a statistically significant correlation with cross-clamping time. Warm blood cardioplegia is safe and supplies adequate myocardial protection during CABG; the more prolonged cross-clamping is, the more myocardial protection is afforded by WCBC.