RESUMEN
Primary myocardial fibrosis (PMF), defined as myocardial fibrosis in the absence of identifiable causes, may represent a common alternative phenotype in various cardiomyopathies and contribute to sudden cardiac death (SCD). No previous definitions of histopathological characteristics exist for PMF. We aimed to evaluate whether common features of fibrosis could be identified. PMF cases (n = 28) were selected from the FinGesture cohort consisting of 5,869 SCD victims that underwent a medicolegal autopsy. Twelve trauma controls and 10 ischemic heart disease cases were selected as reference groups. Further 3 PMF cases and 5 ischemic heart disease cases from autopsies performed in the University of Copenhagen, Denmark, were selected for a validation substudy. Relative area of fibrosis, amount of diffuse and perivascular fibrosis, and location of fibrosis were assessed from left ventricle myocardial samples stained with Masson trichrome. Further evaluations were performed with alpha-smooth muscle actin (α-SMA), vimentin, and CD68 stainings. Mean relative area of fibrosis was 5.8 ± 10.7%, 1.0 ± 0.7%, and 7.0 ± 7.4% in PMF, trauma controls, and ischemic cases, respectively. Fibrosis in the PMF group was mostly located in other sites than the endocardium. Most cases with fibrosis had vimentin-positive but α-SMA-negative stromal cells within fibrotic areas. Histopathologically, PMF represents a heterogeneous entity with variable fibrotic lesions affecting the whole myocardium and a suggested significant role of fibroblasts. These findings may bring validation to PMF being a common manifestation of cardiomyopathies. Evidently, PMF stands out as a particular entity demanding special attention as a cause of SCD.
RESUMEN
The normal human heart contains epicardial adipose tissue (EAT) and myocardial fat. The associations between obesity, myocardial fat, visceral adipose tissue (VAT), and cardiovascular disease are not fully understood. The objective of this study was to estimate myocardial fat using stereological methods and investigate its relations with obesity, EAT, and VAT. To establish the EAT volume, 115 deceased individuals were included, and postmortem computed tomography was conducted on their eviscerated hearts. Six samples from the left and right ventricles (LV and RV) of the heart were stereologically examined to calculate the percentage of myocardial fat. Kidney and omental fat were weighed at autopsy, and the waist-hip ratio was calculated. Females had a slightly non-significantly (p = 0.054) larger proportion of RV fat (13.2% ± 4.4) compared to that in men (11.5% ± 2.7). We found a significant positive correlation between body mass index (BMI) and LV myocardial fat (p = 0.033). In the RV, this correlation was only at the borderline of significance (p = 0.052). The EAT volume was positively correlated with both RV and LV myocardial fat. We found no association with the waist-hip ratio (WHR) or the omental or kidney fat as measures of VAT. The myocardial fat was normal, most prominent in the RV, and correlated with the EAT and, partly, BMI. We found no association with VAT.