Koch's triangle is best described as which of the following?

• A. A region in the left atrial appendage containing the AV node area
• B. A region in the right atrial septal area containing the AV node area; guides safe ablation near the AV node and slow pathway
• C. A portion of the interatrial septum that conducts impulse to the ventricles
• D. A small triangle in the right atrium near the tricuspid valve

Answer: (B)

Koch's triangle is an anatomic landmark in the right atrial septum that contains the AV node and the region associated with the slow pathway, which is why it’s used to guide safe ablation near the AV node. It lies in the right atrial septal area and is bounded by the tendon of Todaro, the ostium of the coronary sinus, and the septal tricuspid annulus. Knowing this location helps electrophysiologists target ablation while minimizing the risk of AV nodal injury, which is crucial when treating AVNRT and modifying the slow pathway. The description identifying this region specifically as the right atrial septal area containing the AV node and its use as a guide for safe ablation near the AV node and slow pathway best captures the true anatomy and clinical purpose. Descriptions placing the region in the left atrial appendage, or describing it only as a general area near the tricuspid valve without the septal landmarks, do not reflect its true location or function.