Teaching Points With 3-Dimensional Mapping of Cardiac Arrhythmia

Abstract

An increasingly used technique for ablation in patients with structural heart disease is substrate mapping. At times, because of the multiplicity of arrhythmia-induced or hemodynamic intolerance in tachycardia, activation or entrainment mapping is not feasible. In these cases, a map of the arrhythmogenic substrate (cataloguing of scar, abnormal myocardium, and normal myocardium during sinus rhythm or a stable arrhythmia) may allow detection of arrhythmogenic channels for the various tachyarrhythmias and can be targeted for ablation1,2 (Figure 1). Figure 1. Upper panel , Posteroanterior view of a left ventricular bipolar voltage map from a patient with scar-related ischemic ventricular tachycardia. The reentrant circuit was found to be perimitral, with the area of slow conduction between a large area of scar (red color) and the mitral valve (not shown in the map). Red dots represent ablation points. At the side of the map, the color-coded bar was set up to assign colors to different bipolar electrograms amplitudes, so that the bipolar potentials greater than 1.5 mV are purple, bipolar potentials less than 0.5 mV are red, and the different hues of yellow-green-blue bipolar potentials are between 0.5 and 1.5 mV. Even though not of general consensus, scar tissue is considered to have local bipolar potentials less than 0.5 mV. Lower panel , Intracardiac electrograms (recording from right ventricular [RV] apex, His, and ablation catheter proximal and distal) during scar-related ventricular tachycardia. Ablation distal records low-amplitude, fractionated, and mid-diastolic potentials from a point embedded in the scar tissue, all characteristics of surviving myocardial fibers that represent areas of slow conduction and arrhythmogenic channels. The unipolar and bipolar signals derived from mapping not only convey timing information used to construct the activation map, but, in addition, the amplitude of the electrogram (voltage) recorded from mapping catheter in contact with the myocardium reflects …