Journal of Pediatric Cardiology and Cardiac Surgery

High-resolution three-dimensional mapping has rarely been used in patients with multiple accessory pathways. We report a 5-year-old girl with a diagnosis of paroxysmal supraventricular tachycardia who was referred to our pediatric unit for catheter ablation. Electrophysiological study revealed a left accessory pathway and orthodromic atrioventricular reciprocating tachycardia (AVRT). After trans-septal puncture, we used the ORION™ high-density catheter and the RHYTHMIA™ Mapping System to map an activation pattern of the left atrium during right ventricular pacing. Activation mapping revealed that the earliest site of atrial activation occurred in the left lateral portion of the left atrium, and, in addition, anterolateral activation sometimes occurred as early as left lateral activation. After the first radiofrequency catheter ablation on the left lateral atrium, narrow QRS complex tachycardia persisted, and the earliest atrial activation occurred in the anterolateral portion. Two AVRTs via separate accessory pathways were diagnosed; those two accessory pathways were 16.7 mm apart. High-resolution activation mapping showed two breakthrough activations via the mitral annulus. The propagated waves collided at the distal portion of the left atrium through the mitral annulus. This case showed that ultra–high-resolution mapping is safe and useful for delineating multiple accessory pathways, even in pediatric patients.