Warm-up phenomenon in adult and elderly patients with coronary artery disease: Further evidence of the loss of "ischemic preconditioning" in the aging heart

Background. A reduction of exercise-induced ischemia in patients with coronary artery disease by means of brief period of exercise followed by resting is called the "warm-up" phenomenon. This phenomenon may represent a clinical counterpart of "ischemic preconditioning." We studied the warm-up phenomenon in both adult and elderly patients with similar angiographic evidence of coronary artery disease, using three exercise tests after excluding the "training effect." Methods. In order to verify the presence of "training effect," three exercise tests were performed in days 1, 3, and 3 ("training" tests). The third test was used as baseline for a successive test, performed after a recovery period of 10 minutes to reestablish baseline electrocardiographic conditions. A third exercise test was performed 30 minutes later ("warm-up" tests). Results. "Training" tests did not differ in all parameters in both adult and elderly patients. "Warm-up" tests showed that time to onset I-mm ST depression was significantly higher (p < .001), whereas ST depression and lime to recovery was significantly lower in the second and third test in adult but not in elderly patients (p < .001). Difference (in seconds) in the time at which I-mm ST depression occurred on first warm-up exercise compared with the second was inversely correlated with age (p < .001). Conclusions. Previous exercise followed by resting is able to reduce the successive exercise-induced ischemia ("warm-up" phenomenon) in adult bur not in elderly patients with coronary artery disease. This is independent of a greater age-related severity of coronary disease and of "training effect." These results confirm the hypothetical age-related reduction of "ischemic preconditioning" in aging heart.