A 60-year-old man with manifest Wolff–Parkinson–White syndrome was referred for catheter ablation. Activation map during sinus rhythm using Rhythmia™ system demonstrated earliest left posterolateral ventricular activation (Panel A). In contrast, retrograde atrial activation during right ventricular pacing showed two breakthrough activations via mitral annulus (Panel B). These propagations presented a collision at the distal site of the left atrium through the mitral annulus. Subsequent ablation for the anterograde and dual retrograde accessory pathways was successfully applied by the mapping guidance. Ultra-high-resolution mapping might be useful to facilitate multiple conduction pathways simultaneously with short mapping time and adequate mapping points quickly.
