Cellular mechanisms of cardiac arrhythmias in the ischemic and reperfused heart

Sudden cardiac death is one of the major causes of mortality in the Western world. Ischemia- induced arrhythmias, principally ventricular tachycardia and ventricular fibrillation, have been suggested as a possible explanation for this pathology. In addition, reperfusion of the ischemic myocardium may also, albeit more rarely, be responsible for the occurrence of ventricular arrhythmias and sudden cardiac death. The two main mechanisms responsible for the initiation and the maintenance of ventricular arrhythmias occurring during ischemia and reperfusion are reentry mechanisms and triggered activities (non-reentrant mechanisms). After a brief overview of the electrophysiological mechanisms, namely the reentrant and non-reentrant mechanisms, involved in the initiation and the maintenance of ischemia and reperfusion arrhythmias, the cellular mechanisms responsible for the genesis of ischemia and reperfusion arrhythmias will be reviewed. Only arrhythmias occurring during the early period of ischemia, a period during which reperfusion may induce a protection of the myocytes, will be reviewed in this chapter. The electrophysiological mechanisms of the arrhythmias occurring during later phases of ischemia and during infarction have been reviewed elsewhere 1 and their cellular mechanisms are still not clearly identified.