Experimental animal studies have shown that repetitive brief coronary occlusions render the heart resistant to myocardial infarction from subsequent, more prolonged, coronary occlusions. This phenomenon in animal models has been called ischemic preconditioning. In a number of clinical scenarios, the second in a series of ischemic episodes appears to be less severe than the first, suggesting that ischemic preconditioning also occurs in humans. If the mediator of preconditioning could be

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... d, it is conceivable that this agent could be administered to patients with coronary artery disease as a myocardial protectant. However, the definite clinical relevance of this interesting experimental finding remains unknown. Unlike the case in animal models subjected to an abrupt occlusion, preconditioning is difficult to study in the clinical setting. This article reviews the findings and limitations of the relevant clinical studies looking for ischemic preconditioning in humans.