Electrophysiology study:
Diagnostic studies were performed under conscious sedation or general anaesthesia. An electroanatomic mapping system was used in all cases. A diagnostic decapolar catheter (Inquiry, Abbott, St Paul, MN) was placed within the CS with proximal poles positioned at the ostium on fluoroscopy. A deflectable ablation catheter (Tacticath, Abbott, St Paul, MN) or multipolar catheter (Advisor HD Grid, Abbott, St Paul, MN) was used to map the cavo-tricuspid isthmus (CTI) and the lateral right atrial (RA) wall during pacing from the CS at a cycle length of 600 ms. Wavefront collision was defined as the latest point on the lateral RA wall where cranial and caudal wavefronts reproducibly met, as illustrated in Figure 1. Full diagnostic studies were performed in all subjects and ablation was then directed at the SVT or AFL substrate as clinically indicated.