Introduction: Perioperative myocardial infarction has a prognostic value for morbidity and mortality after cardiac surgery . The present study was undertaken to investigate whether cardioplegia related myocardial necrosis and lactate release  are predictive for early cardiac dysfunction after CABG surgery.
Method: 20 patients with stabile angina underwent scheduled CABG with cardiopulmonary bypass (CPB). Cold antegrade and retrograde crystalloid cardioplegia with St. Thomas' solution II was used. Mean cardioplegia time was 84 (50-126) min. Blood for cardiac troponin I (Tn I), creatine kinase MB isoenzyme mass (CK-MB) and lactate was simultaneously sampled from arterial and coronary sinus (CS) cannulae before CPB, and at 1, 5, 10, 20 minutes of reperfusion. Arterio-CS differences were calculated. Cardiac index (CI) and right and left ventricular stroke work indices (RVSWI, LVSWI) were measured by thermodilution technique before sternotomy, 15 minutes and 1, 2, 4, 6, 9, 12 hours after discontinuation of CPB.
Results: Before cardioplegia, myocardial necrosis and lactate release were not detectable. Remarkable release of both Tn I and CK-MB to CS appeared from the 1st minute of reperfusion (Fig.). Release of lactate was maximal on the 1st minute of reperfusion (−1.59 ± 0.71 mmol/L), then decreased to pre-clamping values. Early postoperative performance of the heart, in contrast, was not inferior to pre-clamping values. Mean (±SD) pre-CPB CI was 3.14 ± 0.80L min−1 m−2, while after reperfusion the values were 3.99 ± 1.03 at 15 minutes, 4.37 ± 1.29 at 2 hours, 3.67 ± 0.91 at 6 hours, 3.72 ± 0.80 at 9 hours, and 3.99 ± 0.84 at 12 hours, respectively. No correlation between release of Tn I and CK-MB and CI was found.
Discussion: Cardioplegia is associated with irreversible myocardial injury and temporary lactate release. Contractile function of the heart evaluated by pulmonary artery catheter provides little information of the extent of the myocardial damage.
1 Fellahi JL, Gue X, Richomme X, et al. Short- and long-term prognostic value of postoperative cardiac troponin I concentration in patients undergoing coronary artery bypass grafting. Anesthesiology
2 Rao V, Ivanov J, Weisel RD, et al. Lactate release during reperfusion predicts low cardiac output syndrome after coronary bypass surgery. Ann Thor Surg