Localization of the precise origin of idiopathic ventricular tachycardia from the right ventricular outflow tract by a 12-lead EGG: A study of pace mapping using a multielectrode "basket" catheter

Radiofrequency catheter ablation guided by pace-mapping techniques has prov en effective in eliminating idiopathic ventricular tachycardia (VT) origina ting from the right ventricular outflow tract (RVOT). A method for rapidly identifying the origin of VT from 12-lead electrocardiogram (ECG) findings would be helpful for the catheter ablation procedure. The purpose of this s tudy is to precisely localize the origin of idiopathic VT from the RVOT by a 12-lead ECG from a study of multipoint pace mapping. In one patient with premature ventricular complex (PVC) and 3 with VT, a "basket" catheter was deployed in the RVOT for bipolar pacing from 56 sites in the endocardium of RVOT. Under fluoroscopy the pacing sites were classified into the septum a nd free wall. We investigated the QRS morphology in leads, I, II and III; t he depth of the QS wave in leads aVR and aVL; and the height of the initial r wave in leads V-1 and V-2. Pacing was captured in 30-47 of 56 sites (54% -84%). As the pacing sites changed from the anterior to posterior of the se ptum, the QS notch (-) type in lead I shifted through rs to R, while a shif t from R type to rR' or Rr' was noted in leads II and III. As the pacing si tes changed from the anterior to posterior of the free wall, lead I showed a shift from the QS notch (+) type to R, while a shift from rR' to Rr' tar rR' unchanged) was found in leads II and III. The depth of the QS wave in l eads aVR and aVL showed a tendency for aVR to be deeper than aVL toward the posterolateral attachment of both the septum and free wall, whereas aVL te nded to be deeper than aVR toward the anterior attachment. The initial r wa ves in V-1 and V-2 became greater as the pacing site was positioned at a hi gher or more posterior location. These findings may provide more precise an d clinically useful diagnostic information on the site of the origin of idi opathic VT originating from the RVOT by a 12-lead ECG.