A computer system described previously has been used to make epicardial maps of various ventricular arrhythmias. These maps show that epicardial activation during the initiation of arrhythmias is frequently complex. Displays of the activation sequences as isochrone maps and as animated motion pictures show that the first beats of the arrhythmias can be highly variable and, in some tachyarrhythmias exhibiting slow speed of conduction, multiple activation fronts can coexist on the epicardium. These phenomena cannot be adequately recorded with current mapping techniques using a single hand-held probe and emphasize the need for a computerized system to record from numerous sites on the epicardium simultaneously.
