Natural history of late potentials after myocardial infarction

Abstract

Late potentials, detected by signal averaging of the surface electrocardiogram (ECG), are associated with the occurrence of spontaneous ventricular arrhythmias and the induction of ventricular tachycardia (VT) during programmed ventricular stimulation studies in patients with coronary artery disease^1–3. In particular, this association is strongest among patients with a prior myocardial infarction, particularly in the presence of a ventricular aneurysm⁴. Late potentials are thought to arise from small areas of myocardium at the periphery of infarcted muscle where normal surviving muscle fibres are intertwined with fibrous tissue leading to conduction slowing⁵. These signals which are derived from recordings on the body surface correspond in timing with signals directed recorded from the endocardium at the site of origin of VT and are abolished by successful endocardial resection^6,7. Experimental and clinical observations have shown that these signals appear within days of onset of infarction and may disappear again within days or weeks or they may persist for many years; their presence or absence has also been shown to correspond to changes in arrhythmia induction and this may impact on the risk of developing clinical arrhythmias.