Abstract 149: Relationship between Epicardial Fat Thickness and Underlying Coronary Atherosclerotic Plaque Size and Burden

Abstract

A paracrine effect of epicardial fat in underlying coronary atherosclerosis has been proposed, due to the inflammatory role of adipose tissue. Most studies evaluate globally fat (by magnetic resonance) and atherosclerosis (by computerized tomography). We analyzed microscopically, segment by segment, the potential local influence of fat in atherosclerotic plaque size and burden. Thickness of epicardial fat, coronary lumen area, and area delimited by the internal elastic lamina were measured with an image analysis system coupled to a light microscope, and plaque size (area delimited by the internal elastic lamina less lumen area) and burden (plaque area/ area delimited by the internal elastic lamina) were calculated in 192 coronary artery segments from 9 hearts from necropsies of patients that died with coronary atherosclerosis. To compare epicardial and myocardial faces of the arteries, the measures were made in each half; total amounts were also calculated. The relationships between epicardial fat and underlying atherosclerosis, both considering epicardial half and the whole segment, and between total fat and the total arterial segment, were tested by Pearson’s test. Plaque size and burden in each half were compared by paired Wilcoxon signed rank test. We considered correlation strength as r =0.10 to 0.29- weak, r = 0.30 to 0.49- medium, and r = 0.50 to 1.0- strong correlation, and results significant if P < or = 0.05. Results: Correlation coefficients: epicardial face fat thickness - 1) with plaque area at epicardial half - r = 0.22, P <0.01; 2) with plaque burden at epicardial half- r = 0.18, P =0.02; 3) with total plaque area- r = 0.19, P <0.01; 4) with total plaque burden- r = 0.10, P =0.18; total epicardial fat thickness - 1) with total plaque area - r = 0.22, p<0.01; 2) with total plaque burden- r = 0.06, P =0.39. Comparison between halves: area size - mean 1.20 mm at epicardial face and 1.5 mm at myocardial face, P =0.96; plaque burden - mean 33.7% at epicardial face and 45.7% at myocardial face, P =0.98. Conclusion: the correlations were weak and/or non-significant, and the atherosclerotic process involves equally both halves of the coronary arteries; thus our data indicate that there is no significant effect of fat tissue in underlying coronary atherosclerosis.