Improving myocardial protection : the key variables which affect troponin release after CABG

Abstract

Background: Myocardial cell ischaemic injury during cardiopulmonary bypass and aortic crossclamp remains a key limiting factor to patient outcomes in coronary artery bypass grafting. Troponin I has been shown to be an effective indicator of myocardial ischaemic injury and achieves peak levels early post-operatively. Methods: All consenting CABG patients from one centre, during a one year period, were recruited. All surgeries were performed using identical techniques besides the cardioplegia volume and number of doses. Troponin I levels were checked regularly post-operatively until a peak troponin I level was ascertained. All the patient demographics, crossclamp times, bypass times and cardioplegia dosing were analysed using multiple combinations of statistical tools. Results: 172 patients were included in the study and cardiopulmonary bypass (CPB) time was found to be significant as a single variable (p=0.033). The combination of CBP time and ischaemia time (p=0.002) and the combination of CPB time and multidose cardioplegia (p=0.009), were both found to significantly affect peak troponin I levels. Another analysis was performed on the volume of cardioplegia used. While this was not significant as an individual variable it did become significant when combined with ischaemia time at a threshold total cardioplegia volume of 750mls (p=0.026).Conclusions: The conclusion therefore is that using over 750mls of cardioplegia in multiple doses will safely protect against an ischaemia time of up to 62min. However there is no protection against the CPB time, which proved to have the most impact on myocardial cell damage in our practice.