FREQUENCY, EXTENT, AND DISTRIBUTION OF ENDOMYOCARDIAL ADIPOSE-TISSUE - MORPHOMETRIC ANALYSIS OF ENDOMYOCARDIAL BIOPSY SPECIMENS FROM 241 PATIENTS

Features of endomyocardial biopsy specimens (EMB) have been analyzed e xtensively; however, the frequency, distribution, and associations of adipose tissue in EMB taken from patients with failing hearts have rec eived less attention. We analyzed morphologically and morphometrically EMB from 241 patients (159 male, 82 female, mean age 46.6 years, rang e 18-76) for whom six diagnostic clinicopathologic categories (includi ng normality) were separately defined. The mean surface area of EMB, m ean area of quantifiable adipose tissue, and percentage area attributa ble to fat were determined by computer-based morphometry to be 6.5 mm( 2), 0.4 mm(2), and 6.5%, respectively. The mean number of biopsy piece s, number of pieces with fat, and percentage of pieces with fat were 4 .1, 1.1, and 28.9%, respectively. Patients with arrhythmogenic right v entricular dysplasia had greater percentage area attributable to fat ( 19.8% vs. 8.9%;p < 0.0027) and greater number of pieces with adipose t issue (2.9 vs. 1.0, p < 0.0001) than did patients in diagnostic catego ries with the next most fatty EMB. There were no differences between m ales and females in EMB surface area fat or percentage of pieces with fat. Older patients (above the mean age) had greater adipose tissue in EMB (percentage area attributable to fat) than did younger patients ( 8.1% vs. 4.8%;p < 0.01). Body mass index (kg/m(2)) did not correlate w ith percentage EMB tissue area attributable to fat. Larger EMBs (above the mean area) were neither more frequently nor more involved by fat than were smaller biopsy specimens (6.4% vs. 6.6% fat, respectively). Typically, adipose tissue in EMB percolated widely through the myocard ium, and the mean number of EMB pieces did not influence the likelihoo d of finding fat deposits. Fat was intimately associated with blood ve ssels and was frequently associated with small areas of interstitial a nd replacement fibrosis. The high frequency of adipose tissue in EMB a nd the relatively large area constituted by fat in some EMB supports a utopsy observations that focal and widespread fatty infiltration of th e right ventricular endomyocardium is to be expected and reflected in EMB sampling. Excessive myocardial fat may play a pathogenic role in c ardiomyopathy.