This week’s electrogram interpretation:
The following electrogram was recorded during an RF PVI ablation. The ablation catheter was located/ablating on the ridge between the LAA & LSPV at the time of this recording.
What is observed?
Answer
Ablation of Ganglionated Plexi
During ablation notice that the SA node was no longer firing…, these are all V signals except for 1. After ablation ceased, the SA node did begin generating impulses again.
“The heart is innervated by both the extrinsic and the intrinsic cardiac autonomic nervous system (CANS). The extrinsic CANS consists of the ganglia in the brain or along the spinal cord. The intrinsic CANS is comprised of an extensive epicardial neural network of nerve axons, interconnecting neurons & clusters of autonomic ganglia, known as GP (ganglionic plexi), not only on the atria, but also on both ventricles. These GP, most of which are embedded within epicardial fat pads, vary in size, from those that contain just a few neurons, to those that contain over 400 neurons. Notably, the highest density of autonomic innervation is found at the posterior wall of the left atrium, particularly at the pulmonary vein–atrial junction.
The 4 major atrial GP are located in close association to the pulmonary veins (PVs) and each innervate one of the four PVs, as well as the surrounding atrial myocardium. These GP can be identified during an EP study by applying high-frequency stimulation (HFS) (20 Hz) at the respective anatomical locations.
The anterior right GP is located immediately anterior to the RSPV & often extends inferiorly, to the region anterior to the RIPV. The superior left GP is located at the roof of the left atrium, 1–2 cm medial to the LSPV. The right & left inferior GP are located at the inferior aspect of the posterior wall of the left atrium, 2–3 cm below the right & left PVs, respectively. The ligament of Marshal, located between the left atrial appendage and the LSPV, also contains autonomic neurons. There are multiple interconnections among the GP, converging to the SA & AV node through the anterior right GP and inferior right GP, respectively.”
ARGP: anterior right ganglionated plexus
ILGP: inferior left ganglionated plexus
IRGP: inferior right ganglionated plexus
LOM: Ligament of Marshal
SLGP: superior left ganglionated plexus.
Stavrakis, S., & Po, S. (2017, December). Ganglionated Plexi Ablation: Physiology and Clinical Applications. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5739885/
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