Exercise-Induced Myocardial Ischemia Triggers the Early Phase of Preconditioning But Not the Late Phase
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11.03.2009, 13:25
The warm-up phenomenon, i.e., the improved performance during the second of 2 sequential exercise tests in anginal patients,1–5 appears to be caused by a mechanism similar to that involved in limiting experimental infarct size after a brief ischemic episode, i.e., ischemic preconditioning.6 This hypothesis is supported by the demonstration that myocardial oxygen consumption is reduced during the second of 2 sequential exercise stress tests, suggesting increased metabolic efficiency, which is a feature of preconditioning. 2 Furthermore, improvement in ischemic threshold is lost during a third test, performed 2 hours after the second, suggesting that the time course of the warm-up phenomenon is consistent with that of “classic” ischemic preconditioning, because it lasts no longer than 60 to 90 minutes.3,4 However, it is not yet known whether the protection developed after a first exercise-induced ischemic challenge reappears several hours later, similar to the late phase of ischemic preconditioning seen in experimental studies.7 Thus, the aim of the present study was to establish whether exercise-induced ischemic challenge triggers the second window of protection in humans.
