Session S62.1

Visualization of Lesion Transmurality following Radio-Frequency Ablation of Atrial Fibrillation

JJE Blauer*, D Swenson, C Gloschat, J Stinstra,
NF Marrouche, RS MacLeod

University of Utah
Salt Lake City, UT, USA

Radio-Frequency (RF) ablation in the left atrium (LA) has gained popularity for treatment of atrial fibrillation (AF). However, penetration of this procedure has been limited due to high rates recurrence and serious potential side effects. One contributing factor to procedural success is the creation of conduction blocking transmural lesions. Until recently invasive mapping studies were required to assess lesion patency. Now, delayed enhanced MR imaging (DEMRI) has made noninvasive evaluation of LA lesion formation possible. Knowles et al. developed a new approach for visualizing DEMRI lesions by projecting DEMRI data from the tissue volume onto a 3D endocardial surface (ES) model. We have expanded this approach to assess the transmurality of lesions in LA tissue.
The LA ES was isolated using Seg3D in 8 DEMRI patient scans acquired 3mo. post ablation. Using the ES segmentation a triangulated mesh was created using SCIRun. ES nodes were used to define a local region from which myocardial voxels were projected onto surface normals. These projections if under 3mm were divided into three groups of 1mm sections. The weighted average (WA) of voxel intensities (VI) in each projection group was calculated with weighting function (1-VD/MD)^3 (VD is voxel distance from the normal, MD is the max distance). WA values above a scar tissue threshold (3SD above the normal VI) were used to categorize each group. Each nodes region was indexed by mapping the number of supra-threshold groups in each region to the node.
Visualization of the transmurality index on the ES mesh showed lesion patterns consistent with targeted tissue. Of interest, much of the supra-threshold enhancement was not determined to be transmural by this metric. However, areas near the pulmonary veins were more likely to be transmural.
Determining the source of detrimental currents is the primary step in determining the cause of AF recurrence. This technique may clarify the pertinent characteristics of effective lesion creation when correlated with procedural outcome.

(Abstract Control Number: 206)