retrograde cardioplegic delivery as the strongest independent predictor of in-hospital mortality [46]. Warm cardioplegia may resuscitate ischemic myocardium if it can be delivered uniformly but intermittent discontinuation to permit visualiza- tion of distal anastomoses can result in ischemic anaerobic metabolism [47]. The Toronto Group has reported that blood cardioplegia at 29 C (so-called ‘‘tepid cardioplegia’’) can reduce lactate acid production compared with warm (37 C) cardioplegia. This treatment resulted in better contractile function compared with cold (10 C) blood cardioplegia [48]. Others have suggested that patients who have unstable angina or prolonged preoperative ischemia may deplete metabolic reserves and benefit from substrate- enhanced cardioplegia with Krebs Cycle interme- diates, such as glutamate, malate, succinate, or fumarate [49]. Patients who have diabetes have diffuse atherosclerotic disease, which may limit cardioplegic distribution and prevent complete revascularization. Some authors therefore recom- mend both antegrade and retrograde infusions [50]. The rationale is that the different approaches perfuse different myocardial territories and that the combination may provide more homogeneous cardioplegia delivery. The management of patients at risk for low cardiac output syndrome Three categories of patients are at substantial risk. First are those who present urgently for surgery, already in cardiogenic shock, often with a complication of myocardial infarction or in- fective endocarditis. Second is the group Fig. 2 (continued) 165 MAXIMIZING SURVIVAL POTENTIAL IN CARDIAC SURGERY . cardiogenic shock, often with a complication of myocardial infarction or in- fective endocarditis. Second is the group Fig. 2 (continued) 1 65 MAXIMIZING SURVIVAL POTENTIAL IN CARDIAC SURGERY . Some authors therefore recom- mend both antegrade and retrograde infusions [50 ]. The rationale is that the different approaches perfuse different myocardial territories and that the combination may. delivery as the strongest independent predictor of in- hospital mortality [46]. Warm cardioplegia may resuscitate ischemic myocardium if it can be delivered uniformly but intermittent discontinuation