Ablation targets in reentrant ventricular tachycardia

Abstract

Introduction Magnetic resonance imaging (MRI) with late gadolinium enhancement has been used to pinpoint myocardial infarction features in animal models. In swine postinfarction, this imaging technique has been used to identify areas with slow conduction during reentrant ventricular tachycardia (VT). In this model, the reentry isthmus is composed of a small volume of viable myocardium bounded by scar tissue laterally and at depth. During reentrant VT, arcs of conduction block form where scar is present. In proximity to the infarct, the enhanced MRI scan shows a mixture of electrically conducting viable myocardium and nonviable tissue where conduction is slow during VT. The region is termed the heterogeneous zone (HZ) and appears gray in the contrast-enhanced images, as compared with the white infarct scar and dark gray or black normal myocardium. More recently, the relationship between HZ characteristics and reentrant VT inducibility was shown in swine postinfarction. The authors tested the hypothesis that by ablating the HZ in its entirety, reentrant VT would no longer be inducible, whereas when ablation was incomplete, reentrant VT would still be inducible, though possibly with a differing reentrant circuit morphology. They found that only when the HZ was entirely ablated did the reentrant VT become noninducible. In a new study on this topic, published in this issue of HeartRhythm, the feasibility of using the contrastenhanced imaging in postinfarction VT patients to target arrhythmogenic regions before electrophysiologic (EP) study and radiofrequency ablation is assessed.