Cardiac surgery with cardiopulmonary bypass and ischemic cardiac arrest is associated with a wide spectrum of perioperative myocardial ischemic-reperfusion injuries resulting in significant cardiac morbidity, namely contractile dysfunction, myocardial infarction, and low cardiac output syndrome requiring prolonged intensive care and hospital stay. The infusion of glucose-insulin-potassium (GIK) is one of the oldest cardioprotective interventions during cardiac surgery. Although experimental evidence is strong, clinical data remain conflicting. We will investigate the impact of short term GIK on the extent of myocardial injuries as well as on the left-ventricular systolic and diastolic function in 2 high-risk groups of cardiac surgical patients: Patients with cardiac dysfunction undergoing aortocoronary bypass surgery and patients with severe aortic stenosis.