Experimental preconditioning is commonly regarded as a powerful protective phenomenon in case of subsequent ischemia. However, little is known about the applicability of preconditioning as an adjunct to cardioplegic myocardial protection in routine coronary surgery. For this reason, a prospective clinical study (611995 to 4/1996) was initiated to evaluate normothermic ischemic preconditioning prior to crystalloid or cold blood cardioplegic arrest. Preconditioning was performed in two cycles of 5 min ischemia and 10 min reperfusion. Four groups of 7 patients each were compared regarding release of troponin T, creatine kinase-myocardial isoform (CK-MB), lactate, and total CK in coronary sinus effluents over a 12-hour period. In the absence of perioperative myocardial infarction, there were no significant differences in these ischemic and metabolic parameters. Unexpectedly, the heed of postoperative pharmacological inotropic support was greater after preconditioning. These results may indicate that ischemic preconditioning as an adjunct to cardioplegic arrest may be associated with impairment of left-ventricular contractility, thus even exerting potentially detrimental functional effects. Overall, the proven beneficial effects of experimental preconditioning seem not to be directly transferable into the clinical settings.