Sustained ventricular tachycardia: role of the 12-lead electrocardiogram in localizing site of origin.

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Abstract
The QRS morphology of the 12-lead ECG of 41 morphologically distinct ventricular tachycardias (VT) was correlated with their site of origin as determined by catheter and intraoperative mapping. VT patterns (22) had a right bundle branch block (VT-RBBB) morphology and 19 a left bundle branch block (VT-LBBB) morphology. All VT-RBBB arose in the left ventricle [LV]. All 16 VT-LBBB in patients with coronary artery disease (CAD) arose from the LV at sites on or adjacent to the septum. Three VT-LBBB in patients without CAD arose in the right ventricle. The 12-lead ECG could not precisely identify the site of origin in patients with CAD but could differentiate anterior from posterobasal regions, particularly in VT-LBBB. The ECG was less useful in localizing VT-RBBB because of overlapping patterns. General patterns useful in differentiating anterior from posterobasal sites of origin included: the presence of a q wave in leads 1 and V6 was seen in VT-RBBB or VT-LBBB originating anteriorly but not in VT of posterobasal or posterior septal origin; R waves in leads 1 and V1 to V6 in VT-RBBB and in leads 1, V2, V3 and V6 in VT-LBBB were specific for a posterior origin, and not observed in VT of anterior origin; in VT-LBBB with a superior axis, q wave in leads 1 and V6 was specific for origin along the inferior aspect of the anterior septum; all VT-LBBB with an inferior and rightward axis originated from the superior aspect of the anterior septum. Although selected ECG features are useful in locating the origins of VT, precise localization apparently is not possible by the ECG alone.