Patient referred for frequent junctional tachycardia in WPW. ( A 1) From left to right, 12-lead ECG during junctional tachycardia (no pre-excitation is visible). Baseline 12-lead ECG is shown in ( A 2) and the QRS morphology of the WPW is uncommon and should suggest considering the possibility of multiple pathways. After ablation of a right anterior pathway, ECG 3 appeared. This led to the ablation of a right free wall pathway. After this ablation, a left posteroseptal pathway was discovered (ECG 4) and ablated. Electrocardiogram after ablation of the three pathways was recorded (ECG 5) and was similar to the QRS morphology during junctional tachycardia. ( B ) Electrograms during ablation of the first pathway (transition from ECG 2 to 3). With multiple pathways, it is important to look carefully at the surface ECG during ablation (red arrows show the change in morphology) as well as local electrograms. Note the delay of the V component during pathway ablation, despite the persistence of WPW morphology on the surface ECG due to the other pathways.