Intraoperative cardiac troponin T release and lactate metabolism during coronary artery surgery: comparison of beating heart with conventional coronary artery surgery with cardiopulmonary bypass

Objective-To compare cardiac troponin T release and lactate metabolism in c oronary sinus and arterial blood during uncomplicated coronary grafting on the beating heart with conventional coronary grafting using cardiopulmonary bypass. Design-A prospective observational study with simultaneous sampling of coro nary sinus and arterial blood: before and 1, 4, 10, and 20 minutes after re perfusion for analysis of cardiac troponin T and lactate. Cardiac troponin T was also analysed in venous samples taken 3, 6, 24, 48, and 72 hours afte r surgery. Setting-Cardiac surgical unit in a tertiary referral centre. Patients-18 patients undergoing coronary grafting on the beating heart (10 single vessel and eight two-vessel grafting) and eight undergoing two-vesse l grafting with cardiopulmonary bypass. Results-Cardiac troponin T was detected in coronary sinus blood in all pati ents by 20 minutes after beating heart coronary artery surgery before arter ial concentrations were consistently increased. Peak arterial and coronary sinus cardiac troponin T values on the beating heart during single (0.03 (0 to 0.05) and 0.09 (0.07 to 0.16 mu g/l, respectively) and two-vessel graft ing (0.1 (0.07 to 0.11) and 0.19 (0.14 to 0.25) mu g/l) were lower than the values obtained during cardiopulmonary bypass (0.64 (0.52 to 0.72) and 1.4 (0.9 to 2.0) mu g/l) (p < 0.05). The area under the curve of venous cardia c troponin T over 72 hours for two-vessel grafting on the beating heart was less than with cardiopulmonary bypass (13 (10 to 16) v 68 (26 to 102) mu g .h/l) (p <0.001). Lactate extraction began within one minute of snare relea se during beating heart coronary surgery while lactate was still being prod uced 20 minutes after cross clamp release following cardiopulmonary bypass. Conclusions-Lower intraoperative and serial venous cardiac troponin T conce ntrations suggest a lesser degree of myocyte injury during beating heart co ronary artery surgery than during cardiopulmonary bypass. Oxidative metabol ism also recovers more rapidly with beating heart coronary artery surgery t han with conventional coronary grafting. Coronary sinus cardiac troponin T concentrations increased earlier and were greater than arterial concentrati ons during beating heart surgery, suggesting that this may be a more sensit ive method of intraoperative assessment of myocardial injury.