Localization of Precise Origin of Idiopathic Ventricular Tachycardia from the Right Ventricular Outflow Tract by a 12‐Lead ECG: A Study of Pace Mapping Using a Multielectrode “Basket” Catheter

Abstract

Radiofrequency catheter ablation guided by pace-mapping techniques has proven effective in eliminating idiopathic ventricular tachycardia (VT) originating 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 study 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 and free wall. We investigated the QRS morphology in leads, I, II, and III; the depth of the QS wave in leads aVR and aVL; and the height of the initial r wave in leads V1 and V2. Pacing was captured in 30-47 of 56 sites (54%-84%). As the pacing sites changed from the anterior to posterior of the septum, the QS notch (-) type in lead I shifted through rs to R, while a shift from R type to rR' or Rr' was noted in leads II and III. As the pacing sites 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' (or rR' unchanged) was found in leads II and III. The depth of the QS wave in leads 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 tended to be deeper than aVR toward the anterior attachment. The initial r waves in V1 and V2 became greater as the pacing site was positioned at a higher or more posterior location. These findings may provide more precise and clinically useful diagnostic information on the site of the origin of idiopathic VT originating from the RVOT by a 12-lead ECG.

Prevalence and Electrocardiographic Characteristics of Idiopathic Ventricular Arrhythmia Originating in the Free Wall of the Right Ventricular Outflow Tract

“…Although several studies have described the ECG characteristics of OT-VT/PVC originating from the free wall of the RVOT, 3,4,14,15 we have not found any that determined the prevalence and ECG characteristics of VT originating from the RVOT free wall in a considerable number of patients.…”

“…Two paced mapping studies found the QRS morphology in lead I to be useful in distinguishing a posterior from anterior origin of OT-VT/PVC, and that an RS or a QS pattern of QRS morphology in lead I indicated the leftward and anterior sites of the RVOT free wall. 14,15 Few studies have considered the relationship between the QRS morphology in lead I and the specific location of a tachycardia focus within the free wall in patients with FW-VT/PVC; 14,15 of them, Dixit et al reported that only 1 of 7 FW-VT/PVC cases showed an origin from the anterior portion of the RVOT free wall. 14 In the present study, however, all FW-VT/PVC showed an RR' pattern in lead I, indicating a likely origin in the posterior portion of the RVOT free wall.…”

Positive QRS Complex in Lead I as a Malignant Sign in Right Ventricular Outflow Tract Tachycardia

“…The RVOT-VPCs with a positive QRS wave in lead I usually arise from the posterior attachment side of the septum or free wall. 11 As shown in Figure 4, in 9 of 14 patients, the final successful ablation sites in the present study were also on the posterior attachment of the RVOT.…”

Catheter Ablation for Ventricular Tachycardia

“…70,71 Deeper S waves in aVL than in avR suggest a leftward superior focus, and this ratio decreases with sites located more rightward and inferior in RVOT. 72 Precise localization relies on combined use of pace mapping and activation mapping. In most patients, a site with a pace map QRS that exactly matches that of VT can be identified at or very close to the VT focus, but excellent pace maps may be obtained several millimeters distant from the earliest activation.…”