Post-Conditioning during PCI in Acute Myocardial Infarction: Continued Difficulty in Translation
"Delaying the postconditioning intervention for even a few minutes while changing balloon catheters, or while allowing balloons to remain deflated beyond the period of time suggested by the algorithm, may abrogate the cardioprotective advantage of postconditioning" from Kim, H, et al1
The ability of myocardium to protect itself under lethal ischemic conditions- so called ischemic conditioning- is a remarkably robust and reproducible experimental phenomenon demonstrable via direct measure of infarct size in virtually all animal models tested.2 Despite inferences from the analysis of surrogate end-points in clinical studies, e.g., biomarker elevation, ST-segment shift, anginal discomfort (either preceding or accompanying ischemia), there are as yet no clinical studies directly assessing infarct size reduction consequent to pre-conditioning , as originally described by Murry, et al in a canine model.3 Given the impossibility and implausibility of predicting exactly when an acute myocardial infarction (AMI) will occur in humans and the necessity for the pre-conditioning stimulus to be applied before the ischemic insult, it is clear that pre-conditioning human myocardium imminently facing infarction will likely not be achievable. However, this is a needlessly harsh refutation of the existence and other potential clinical benefits of ischemic pre-conditioning in humans during percutaneous coronary intervention4, open heart surgery5, ischemia-related arrhythmogenesis6- all reasonable models for the predictable and reproducible induction of myocardial ischemia in humans.
- Received September 8, 2013.
- Accepted September 10, 2013.