The purpose of our study was to compare the efficiency of levosimendan and preventive intra-aortic balloon pump in high-risk cardiac patients (left ventricular ejection fraction <35%) operated under cardiopulmonary bypass. In 20 patients, intra-aortic balloon pump was started 16-18 h before surgery; another 20 had a levosimendan infusion starting after induction of anesthesia with an initial bolus of 12 μg·kg(-1) for 10 min, followed by 0.1 μg·kg(-1)·min(-1) for 24 h. Postoperative complications, hemodynamics, and markers of cardiac damage were analyzed. In the levosimendan group, cardiac index was significantly higher 5 min after cardiopulmonary bypass, at the end of the operation, 2 and 4 h after perfusion, compared to the intra-aortic balloon pump group. The level of troponin I in the levosimendan group was significantly lower at 6 h after the operation. Intensive care unit stay was significantly shorter in the levosimendan group. It was concluded that the use of levosimendan in high-risk cardiac patients is as effective as intra-aortic balloon pump, in terms of maintaining stable hemodynamic during and after operations under cardiopulmonary bypass. The lower level of troponin I at 6 h postoperatively suggests cardioprotective properties of levosimendan, but requires further investigation.