Figure 2.

Sequence of noncontact left ventricular isochronal maps demonstrating an episode of pacing-induced ventricular tachycardia initiation from patient 2. Flat maps represent the entire left ventricular endocardium cut along one border and laid open. Black region represents scar. Light blue lines represent lines of functional block. Arrows show direction of propagation of activation. Change of isochrone color represents 10-ms intervals in activation, progressing from white to purple (illustrated on the scale adjacent to panel 1). The corresponding surface ECG is shown at the top with numbers pertaining to map panels below and lines representing the point in time and duration of each map. In this and all subsequent figures, the base of the left ventricle is at the top of each panel and the apex at the bottom. See text for discussion.