Radiofrequency ablation sites in Koch's triangle

Schematic representation of Koch's triangle which is bounded by the tricuspid ring and the tendon of Todoro. Koch's triangle can be divided into thirds: the anterior contains the compact AV node; the posterior contains the coronary sinus; and the middle or mid-septal third is between the anterior and posterior portions. The anterior third is associated with fast pathways, and the middle and posterior thirds with slow pathways. The anterior and posterior approaches to ablate the fast and slow pathways, respectively, are indicated by the position of the catheters (shown in green).