What is happening in this electrogram?
What is observed in the following electrogram?
Catheters: HRA, His, CS, RV. All catheters are in the usual positions.
Interpretation Steps:
- Determine Pacing Site
- Did we capture?
- Did it conduct to the next chamber?
- What was the activation pattern?
Answer:
Throughout the electrogram, pacing is occurring via the RV catheter placed at the RV apex. Ventricular capture was observed with each impulse as well as conduction to the atrium. However, the activation pattern changed halfway.
The first 3 impulses show eccentric (abnormal) activation to the atrium with the earliest atrial signal on CS 1,2.
The last impulses show concentric (normal) activation to the atrium with the earliest signal atrial signal on the His channels, followed by proximal to distal CS.
This is an example of retrograde block of an accessory pathway at 400 ms. This is not a very rapidly conducting pathway (at least not retrogradely).
For more information, please refer to the Understanding EP: A Comprehensive Guide
