Atrial fibrillation (AF) is the most frequent sustained cardiac arrhythmia. AF is shown to be a progressive disease, which is strongly associated with important structural (morphological and histological), electrical and mechanical remodeling of the left atrium (LA). Adipose tissue accumulation has been shown to be a risk factor in AF. We set out to explore the connection between adipose tissue coverage of the LA surface, for both the complete LA and specific regions and the progression of AF. In this study we propose a methodology to study the regional coverage of the left-atrial wall with adipose tissue based on magnetic resonance data. Validation was performed in a sheep model. While the total amount of left-atrial adipose tissue was higher in the sheep with AF, no changes in regional coverage were observed.