[Post-infarction, myocardial ischemia: clinical importance and risk factor]

Abstract

The myocardial scar, left behind by an infarct, makes up a potential substrate for complex ventricular arrhythmias due to the presence in such tissue of electrical inhomogeneity, altered refractoriness, and abnormal conduction properties, which facilitate the induction of reentrant arrhythmias and the release of abnormal automatic responses of the partially repolarised cells. The mechanism(s) by which complex ventricular arrhythmias is/are transformed into malignant arrhythmias has/have not yet been definitely proven. The observation that coronary revascularization - in patients with ischaemic heart disease surviving out of hospital cardiac arrest - improves the prognosis, indicates that transient ischaemic attacks might be the trigger of malignant ventricular arrhythmias in patients with prior myocardial infarction. Patients with large infarct scars (heart failure) have an increased incidence of complex ventricular arrhythmias, death, and ischaemic events. Antiarrhythmic medical intervention does not improve the prognosis in these patients. Intervention with ACE-inhibitors reduces the prevalence of complex ventricular arrhythmias, the incidence of death, and reinfarction, but not arrhythmic death, indicating that residual ischaemia might be the major risk variable in patients with heart failure. Ischaemia is one of several risk markers for transient supraventricular arrhythmias in patients recovering from an acute myocardial infarction (AMI). In addition, anti-ischaemic intervention in patients recovering from AMI suppresses residual myocardial ischaemia and thereby reduces major events.