We have identified 4 groups of patients that will allow us to prospectively and systematically evaluate TSI in this young population. The first group is those patients with supraventricular tachycardia and the Wolff-Parkinson-White (WPW) syndrome. These patients have an accessory AV connection (AC) that allows electrical activity to bypass the normal AV node and excite the ventricles prematurely. In doing so, the result is a loss of the normal, midline ventricular activation pattern for a dysynchronous activation pattern. There have been small reports of this chronic ventricular dysynchrony potential playing a role in depressed myocardial performance.(15) Standard therapy for patients with WPW and clinical SVT includes invasive intracardiac electrophysiology study (EPS) with possible radiofrequency ablation (RFA) in order to eliminate the AC. These patients are then left with normal conduction over the AV node, presumably restoring the midline activation sequence.