Clinical Electrophysiology -> Atrial Fibrillation & Atrial Flutter: -> Physiology D-PO02 - Poster Session II (ID 47) Poster

D-PO02-235 - Areas Of High Intensity In In-vivo Mri Correlate To Areas Of Slow Conduction Using High Density Mapping (ID 269)


Background: Slow conduction zones in the left atrium (LA) may be regions of interest in sustaining atrial fibrillation (AF).
Objective: We aim to show that conduction velocity (CV) decreases in areas of high intensity compared to low intensity regions in in-vivo late gadolinium enhancement (LGE) MRI scans.
Methods: High density electrophysiology studies were performed on a chronic rapid atrial paced canine model (n=7) using the Orion catheter and the Rhythmia (Boston Scientific) mapping system. Animals were paced for >6 months and had sustained AF with LA activation times recorded in sinus rhythm after cardioversion. CV was calculated using the triangulation method. In-vivo LGE-MRI scan was done in a 3T scanner. The LA wall was segmented, and the highest 30% intensity marked as high intensity region. The anatomical LA CV map and the MRI geometry were registered, and the CV in high and low intensity regions was compared using Welch’s t-test.
Results: The mean number of EGMs used for each CV map was 13900 ± 5000. The overall mean LA CV for all animals (n=7) was 0.88 m/s [0.76-0.95], with a mean CV of 0.81 m/s [0.67-0.91] in high intensity regions and 0.93 m/s [0.79-0.99] in the low intensity regions. For all animals, there was a significant difference (p<0.01) in the CV between the high and low intensity regions of the LA, with a mean difference of 0.12 m/s and a mean Cohen’s D effect size of 0.50.
Conclusion: We show reduced CV in enhanced regions of the in-vivo LGE scan, which relates to atrial structural remodeling. This indicates that fibrosis may play a key role in conduction slowing in the LA and important in allowing reentrant circuits to occur to sustain AF.