Preconditioning and its potential role in myocardial protection during cardiac surgery

Myocardial preconditioning is the phenomenon whereby a brief stress to the heart (e.g., ischemia, hypoxia, etc.) prior to a prolonged period of ischemia renders the heart more resistant to ischemic injury. The cardioprotective effects of preconditioning include reduced infarct size and reduced ventricular arrhythmias. Preconditioning also is associated with beneficial metabolic effects during the prolonged ischemia, effects that also are observed during intermittent cardioplegia. However, there are conflicting reports about the effects of preconditioning on postischemic ventricular function. Although adenosine is thought to be the endogenous mediator of ischemic preconditioning, there are some important differences between adenosine and ischemic preconditioning mediated cardioprotection.