In 1325 open heart operated (OHO) patients with a perioperative mortality of 5.8% the incidence of septicemia and perioperative myocardial infarction (PMI) were much higher in a cohort of 110 patients given intra-aortic balloon pump (IABP) support during the operative course. Analysis of this cohort showed that peri/postoperative insertion of the pump, the presence of disease in the descending branch of left coronary artery (LAD) and the need of more than one saphenous vein graft were risk factors for PMI. The presence of LAD disease was the only independent risk factor for PMI with an odds ratio (OR) of 4.62. Well known risk factors such as NYHA functional class, emergency, low left ventricular ejection fraction (EF) or elevated end diastolic pressure (EDP) were not prognostic of PMI. Thus, the intraoperative seemed to be more important than the preoperative risk profile for the development of PMI. Independent risk factors for the development of septicemia were the duration of IABP with an OR of 1.5 for each pump day and implantation of a valve prosthesis with an OR of 6.3. To avoid septic complications, this study suggests pump removal as soon as possible.