This week’s electrogram interpretation:
Describe the activation pattern in the following electrogram.
What is the most likely rhythm?
Answer
Left Atrial Flutter
- The activation sequence of the CS is from proximal to distal.
- Based on just the electrogram, this is a left atrial flutter. However, further mapping is needed.
- Left-sided atrial flutter may also be seen with proximal to distal activation with CS 9,10 displaying the earliest activation and CS 1,2 the latest. So, if the activation is proximal to distal CS, it does not rule out left atrial flutter. The CS activation is dependent on the direction of the wave of depolarization or circuit in the left atrium. For example, if the circuit is traveling around the mitral annulus in the clockwise direction, the CS will display distal to proximal activation like in this example. If it is traveling in the counterclockwise direction the activation sequence will be reversed – proximal to distal.
- The following propagation map displays a counterclockwise mitral annular flutter. Notice how the wave of depolarization is observed first on the distal CS and lastly on the proximal electrodes.
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For more information: EP Essentials – Understanding EP: A Comprehensive Approach – sections on Atrial Flutter.
