INTRAOPERATIVE RELEASE OF TROPONIN-T IN CORONARY VENOUS AND ARTERIAL BLOOD AND ITS RELATION TO RECOVERY OF LEFT-VENTRICULAR FUNCTION AND OXIDATIVE-METABOLISM FOLLOWING CORONARY-ARTERY SURGERY

Objective-To investigate the intraoperative release of troponin T duri ng uncomplicated coronary artery surgery and to determine its relation to ischaemic time and to recovery of left ventricular function and ox idative metabolism. Design-A prospective, observational study. Setting -Cardiac surgical unit in a tertiary referral centre. Methods-Troponin T, creatine kinase, and lactate were analysed from arterial and coron ary sinus samples taken before operation, and 1, 4, 6, 10, 20, 35, and 45 minutes after cross clamp release. Net myocardial troponin T relea se and lactate extraction were derived from their respective arteriove nous differences. Haemodynamic measurements were made using a thermodi lution pulmonary artery catheter. Patients-45 patients, mean (SD) age 62 (9) years, with two Or three vessel coronary artery disease and chr onic stable angina undergoing routine coronary artery surgery. Results -Before operation, troponin T concentrations were not raised, but with in one minute of cross clamp release they increased progressively in b oth coronary sinus and arterial blood for the entire 45 minutes of rep erfusion studied. Coronary sinus troponin T concentrations were consis tently higher than arterial concentrations at all time points (p < 0.0 01), indicating net troponin T release by the myocardium. Peak net tro ponin T release and area under the curve of net troponin T release cor related closely with ischaemic time (r = 0.58 and r = 0.61, p < 0.0001 for both). Area under the curve of arterial troponin T concentration was also significantly correlated with ischaemic time (r = 0.44, p < 0 .01). Patients with cross clamp times longer than 72 minutes (upper qu artile for ischaemic time) had greater troponin T release, delayed rev ersion to lactate extraction, and lower left ventricular stroke work i ndex three hours after surgery, compared with patients who had short ( < 50 minutes, lower quartile) and intermediate (51-71 minutes, interqu artile) cross clamp times. Peak net troponin T release and area under the curve of arterial troponin T concentration were inversely correlat ed with left ventricular stroke work index three hours after surgery ( r = -0.57, r = -0.38, p < 0.01). Conclusions-Troponin T concentrations increased in every patient after cross clamp release, and were consis tently higher in coronary sinus blood than in arterial blood, indicati ng net myocardial release of troponin T during the period of reperfusi on. Intraoperative net troponin T release has functional significance, as it is closely related to ischaemic time and reflects delayed recov ery of left ventricular function and oxidative metabolism; therefore, its measurement may contribute to the perioperative assessment of myoc ardial injury sustained during coronary artery surgery.