Electrocardiographic manifestation of anatomical substrates underlying post–myocardial infarction tachycardias

Abstract

There are great differences in the type of fibrosis that composes an infarcted area. The type of fibrosis will affect the characteristics of recorded extracellular electrograms. Patchy fibrosis, which is often present in the infarcted zone, gives rise to fractionated electrograms. The amount of fractionation has been shown to increase with infarct aging. In addition, the recording mode being unipolar or bipolar is of importance for interpretation of the electrograms, and it will be shown that the 2 modes are, in fact, complimentary. Surviving myocardial fibers in the infarcted area give rise to conducting tracts that may set up a reentry circuit. Activation in these tracts may be detected during tachycardia as diastolic and during sinus rhythm as late potentials. However, not all sites that generate diastolic potentials during tachycardia will reflect late potentials during sinus rhythm. For ablation of infarct-related tachycardias, the distance between surviving bundles and the recording site is of importance, and this item will be addressed.