Benoit Desjardins MD, PhD, Presenter: Nothing to Disclose

Fabien Squara MD, Abstract Co-Author: Nothing to Disclose

Greg Supple MD, Abstract Co-Author: Nothing to Disclose

Francis Marchlinski MD, Abstract Co-Author: Nothing to Disclose

A complication of left atrial ablation therapy for atrial fibrillation is injury to the right phrenic nerve (RPN). The location of the RPN is estimated during the ablation procedure by attempted electrical excitation of the RPN from multiple locations inside the left atrium. Locations where excitations are captured by the RPN are assumed to be in close proximity to the path of the RPN. This determines a danger zone where ablation lesions are at risk of causing RPN injury. The purpose of this project is to determine the size of this danger zone from Computed Tomographic Angiography (CTA) datasets.

In 19 consecutive patients undergoing left atrial ablation therapy, the path of the RPN was estimated by electrical excitation of the RPN at 10mA and 50mA from different points at the endocardial surface the left atrium. Palpation of diaphragm contraction was used to determine whether there was capture or non-capture of the excitation by the RPN. After the procedure, the 3D path of the RPN was identified and segmented from CTA datasets using either visualization of the RPN or the right pericardiophrenic artery. The segmented RPN was then merged with the cardiac ablation dataset, and minimal distance of each electrical excitation site to the path of the RPN was determined and correlated with capture or non-capture of each electrical excitation by the RPN.

The mean distance between the RPN and the electrical excitation sites at 50mA was 15.5 ± 5.9mm for captured sites vs. 19.0 ± 7.2mm for non-capture sites (p<0.0001), and 11.0 ± 6.0mm vs. 17.7 ± 7.3mm for capture vs. non-capture sites at 10mA (p = 0.042). A distance < 9.4mm predicted RPN capture at 10mA with 87% sensitivity and 80% specificity.

There is good correlation between minimal distance between the left atrial electrical excitation site and the RPN and capture versus non-capture of the electrical excitation by the RPN. This data helps determine the size of the danger zone around the path of the RPN where ablation lesions at different intensities are at risk of affecting the RPN and causing possible injury.

CTA is often performed before ablation therapy to assess pulmonary vein anatomy. In addition, radiologists can also identify the path of the RPN from CTA datasets, and use this information to describe the extent of a danger zone around which ablation lesions could injure the RPN.

Desjardins, B, Squara, F, Supple, G, Marchlinski, F, Use of Computed Tomographic Angiography to Determine Extent of Danger Zone for Phrenic Nerve Injury during Left Atrial Ablation Therapy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14016289.html