What is the normal AH interval?

What is the normal AH interval?

• A. 10-40 ms
• B. 50-140 ms
• C. 160-200 ms
• D. 0-20 ms

Answer: (B)

The AH interval measures the conduction time through the AV node—from the atrial activation to the His bundle activation. This nodal conduction time is normally in the roughly 50 to 140 milliseconds range, with some variation due to autonomic tone and baseline AV nodal properties. Values longer than about 140 ms point to slowed AV nodal conduction or AV nodal disease, while very short values can suggest conduction bypass through an accessory pathway in the appropriate clinical context. The other options fall outside the typical AV nodal conduction window, so the normal range is around 50–140 ms.

The AH interval measures the conduction time through the AV node—from the atrial activation to the His bundle activation. This nodal conduction time is normally in the roughly 50 to 140 milliseconds range, with some variation due to autonomic tone and baseline AV nodal properties. Values longer than about 140 ms point to slowed AV nodal conduction or AV nodal disease, while very short values can suggest conduction bypass through an accessory pathway in the appropriate clinical context. The other options fall outside the typical AV nodal conduction window, so the normal range is around 50–140 ms.