Triangle of Koch

Triangle of Koch – Anatomy & Key Points

Definition:
The Triangle of Koch is an anatomical area in the right atrium of the heart that is critically important in cardiac electrophysiology because it contains the atrioventricular (AV) node.

Boundaries

The triangle is roughly triangular in shape and is defined by three anatomical landmarks:

1. Tendon of Todaro (superior border)
   • Fibrous structure extending from the Eustachian valve to the central fibrous body.
   • Important as a landmark for locating the AV node.
2. Coronary sinus ostium (posterior-inferior border)
   • The opening of the coronary sinus into the right atrium.
3. Septal leaflet of the tricuspid valve (anterior-inferior border)
   • The part of the tricuspid valve attached to the interventricular septum.

Contents

• AV node: The main conduction node between atria and ventricles.
• His bundle origin: The AV bundle arises near the apex of the triangle.

Clinical Relevance

• Electrophysiology procedures:
  • The triangle is the key landmark in catheter ablation of arrhythmias.
  • Avoiding damage to the AV node is critical during ablations near the triangle.
• Arrhythmias:
  • Reentrant tachycardias often involve pathways close to or within the triangle.

Mnemonic

• “TAC” for Triangle of Koch:
  • T = Tendon of Todaro
  • A = AV node (apex)
  • C = Coronary sinus ostium

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