LA Fibrosis Assessment
Quantification of LA fibrosis was obtained using methods previously
described(19). The LA wall was segmented manually and regions of
fibrosis in LGE-MRI images were defined by an intensity threshold
determined by expert inspection. Fibrotic tissue is detected when its
intensity is two to three standard deviations above the mean of the
normal tissue intensity. A 3D LA fibrosis map was created using volume
rendering module in Corview software (Marrek Inc., Salt Lake City, UT).
Inter-observer and intra-observer reproducibility for this technique was
previously reported (17). Fibrosis was represented as the volumetric
percentage of left atrial wall enhancement.