Ventricular arrhythmias in acute myocardial ischemia: risk factors, mechanisms and prognostic value

Malignant ventricular arrhythmias (VA) are a major contributor to mortality in myocardial infarction (MI). Although early revascularization has markedly reduced the incidence of late and secondary VA, the occurrence and fatality rates of VA during the prehospital stage remain high. In ST-elevation myocardial infarction, most VA occur within the first 24 hours, with only a small proportion observed during the second day. The risk of early ischemic VA is associated with short time from symptom onset, potassium imbalance, complete coronary artery occlusion, large ischemic area, and new-onset atrial fibrillation. Some patients exhibit a persistent susceptibility to VA during acute ischemia, which may remain clinically relevant after discharge and manifest as recurrent VA during subsequent acute coronary events, possibly reflecting an underlying genetic predisposition. Ventricular fibrillation may be predicted by ECG markers of depolarization delay, repolarization dispersion, and action potential prolongation, with their diagnostic value depending critically on timing during ischemia.