Figure 3.

Sequence of noncontact left ventricular isopotential maps from patient 8 demonstrating a transitional beat prior to monomorphic ventricular tachycardia. Flat isopotential maps represent the entire left ventricle cut along one border and laid open. Gray areas are infarct scar. Red rectangular symbol is the pacing site. Purple represents resting endocardial potential that changes through a spectrum of colors on activation, with white representing maximal change of negative potential. Arrows show direction of activation. Light blue lines represent lines of functional block. Panel at the top shows surface ECG lead III with reconstructed electrograms beneath (Virtual 1–6). White circles in panels 2 and 8 indicate sites where reconstructed electrograms were recorded. A ventricular premature beat occurs after S3, then a transitional beat and then sustained monomorphic ventricular tachycardia. Vertical red lines are lettered and correspond with the panels below. See text for discussion.