This week’s electrogram interpretation:
What is observed in the electrogram?
Answer
Manifest Entrainment of Right Atrial Flutter
The rhythm on the right half of the electrogram is atrial flutter with activation from proximal to distal coronary sinus. However, the CS activation sequence alone does not rule out left atrial flutter. If the flutter circuit is traveling around the mitral valve in the counterclockwise direction it will demonstrate this sequence.
So, how do you determine if this is a right or left atrial flutter?
…Entrainment.
In this example, entrainment was performed via CS 1,2 (distal). To entrain, pace 20 ms faster than the tachycardia cycle length. After pacing, the tachycardia must continue and the post pacing interval is measured on the pacing channel from the pacing artifact to the return A. The tachycardia cycle length is then subtracted from the PPI to determine the distance the pacing electrodes are from the tachycardia circuit. If the resulting number is less than 30 ms the pacing electrodes are within the circuit.
In this example, 420 (PPI) – 300 (TCL) = 120 ms.
With the PPI – TCL of 120 ms, the pacing electrodes are not within the tachycardia circuit. This is a right atrial flutter. Also of note is the manifest appearance. The pacing morphology is different from the tachycardia morphology. If the pacing electrodes are within the critical isthmus of the tachycardia circuit the PPI – TCL will be less than 30 ms with concealed entrainment in which the pacing morphology matches the tachycardia morphology.
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For more information: EP Essentials – Understanding EP: A Comprehensive Approach – section on atrial flutter entrainment.
