A His bundle catheter is primarily used to observe which of the following?

• A. Distal AVN
• B. Proximal AVN
• C. AVN conduction time
• D. Bundle of His length

Answer: (A)

The His bundle catheter is placed right at the junction where the AV node transitions into the His-Purkinje system, so it directly samples signals from the distal portion of the AV node as the atrial impulse travels toward the ventricles. This position lets you observe how quickly the impulse passes through the AV node itself, i.e., the AV nodal conduction. That’s the primary use of this catheter: to assess AV nodal conduction properties by recording nodal activity and measuring the related conduction times. The distal AVN region is the most accessible and informative site for this purpose with a His bundle catheter. Proximal AVN would be upstream and harder to sample from this catheter, the length of the Bundle of His isn’t a measured observation here, and AVN conduction time is a functional parameter rather than the location being observed.