LAUSR

A ventricular tachycardia (VT) with a left bundle branch block (BBB) pattern exhibited the earliest activation (EA) at the left ventricular basal septum near the His bundle with no excellent pace map (PM). Radiofrequency ablation at the right ventricular basal septum (opposite site of the EA site) changed the QRS morphology of VT to a right BBB pattern that matched a PM at the opposite site in the left ventricle. VT ablation was successful at the earliest activation site. The VT should have originated from an intramural origin with preferential pathways to the endocardial breakout sites in the right and left ventricular septum.