This week’s electrogram interpretation:
What signal is circled in the following electrogram, recorded after PVI was performed?
The PV catheter is in the LSPV and the ablation catheter (ABL) is in the left atrial appendage.
Answer
Left Atrial Signal – Not PV Signal
It may be difficult to differentiate between the far-field LA signal and the local pulmonary vein signal. In this case, pulmonary vein isolation was performed and the following signal still remained on the PV catheter. Recall, the left atrial appendage (LAA) is located anterior to the LSPV, so far-field signal is often observed in the vein. This does not look like the typical far-field LAA signal as a far-field signal will most often have a blunted waveform such as seen in the V wave throughout the channels.
This patient had a very large LAA in close proximity to the LSPV; therefore, the physician performed a pacing maneuver to differentiate between LAA and LSPV signal. The ablation catheter is positioned in the LAA (notice the large A and V) and pacing is performed. The sharp signal that was observed on the PV catheter was “sucked in” or brought in with pacing. This differentiates between LA (or LAA) signal and PV signal. Pulmonary vein signal would not be brought in with LAA pacing. Therefore, the vein was determined to be isolated.
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For more information: EP Essentials – Understanding EP: A Comprehensive Approach – section on atrial fibrillation.
