Relationship between epicardial fat and coronary atherosclerosis: a necropsy and morphometric study in human hearts

Abstract

Atherosclerosis is a result of chronic inflammation, involving increased rates of pro inflammatory cytokines, elevated vascular permeability and a large recruitment of leukocytes. The lipid accumulation occurs either in intra and extra cellular spaces and, added with the thickened intimal layer, due a smooth muscle cells proliferation, have a essential rule in the pathogenesis of the atheroma plaque. It's well determined that the increased visceral adiposity ant the major expression of multiple pro-inflamatory cytokines induces atherosclerosis through a paracrine effect.There's a demand to elucidate the role of epicardial fat in coronary atherosclerosis. The epicardial fat secretes an important level of cytokines and adipocines and, in histologic studies, it was seen that the amount of epicardial fat and it's infiltration by macrophages are related to inflammatory properties of atherosclerotic plaques. This current study will try to identify if there's relationship between the amount of epicardial fat and the atherosclerotic plaque area and the quantity of fatness in coronary arteries of 30 hearts of non identified adults patients that we're submitted to a necropsy study in the laboratory of pathologic anatomy of Instituto do Coração HC-FMUSP. Also, it will be verified if there is a predominant distribution of atherosclerotic lesions inside the coronary according to the amount of adipose tissue adjacent epicardial and myocardial sides. Simultaneously, it will be evaluated the eventual influence of dislipidemic disturbances, obesity and diabetes in these cases.After the fixation process of the coronary arteries using formaldehyde at a pressure of 105 mmHg, the major segments will be dissected, preserving the adjacent adiposity. Segments with invasive procedures will not be included. After decalcification, the arteries will be cutted with 0,5 cm of thickness and submitted through the habitual histologic manufacturing and then through hematoxylin and eosin coloration. Of each case, two samples will be selected randomly and submitted trough a congelation method and colored by Sudan IV, used for adipose tissues. Measurements of the thinnest layer of epicardial adipose tissue and of the area occupied by atherosclerotic plaque in epicardial and myocardial halves in both methods will be done using photographies obtained by a microscope linked to a image analyzer program. It will be collected from the patients records data about other conditions associated, as presence or not of diabetes and dislipidemia, glucose blood rates at admission, cholesterol and triglycerides blood rates, body mass index and presence or not of a treatment for the vigent comorbidities.For the statistic analysis it will be used correlations tests, like Pearson's or Spearman's tests, T test for matched data e, eventually, multivariate data analysis. In all of them, it will be considered significant results with pd0,05.