Histological and morphometric analysis of dilated cardiomyopathy with special reference to collagen IV expression

Introduction: Collagen distribution alterations are well known in dilated cardiomyopathy. There are also changes in microvasculature along with other histomorphorphological features. Aims and Objectives: To study the histomorphological features of DCM along with their quantitative correlation with LVEF. Alterations in collagen IV distribution pattern and microvasculature in DCM were also evaluated. Materials and Methods: The present study includes 34 right ventricular endomyocardial biopsies, 7 explanted native hearts and 41 autopsy control hearts. Sections were taken from lower half of right interventricular septum and stained for H and E, Masson trichrome and immunohistochemistry for CD34, SMA and Collagen IV to study the histological features, pattern of fibrosis, capillary and arteriolar distribution and collagen IV expression respectively. Morphometric analysis was carried out in all cases and controls using Image analysis software Image pro plus 7 and correlated with left ventricular ejection fraction. Results: The histomorphological changes of DCM include myocyte hypertrophy, nucleomegaly, and interstitial fibrosis. Interfiber fibrosis was the commonest. There was evidence of myocarditis, ischemic change and vessel wall alterations. Considerable alteration in Collagen IV distribution was observed with reduction in intensity and proportion of staining around myocytes quantified using Allred scoring against uniform pericellular staining in controls. Morphometric analysis revealed significant increase in nuclear area, myocyte width, percentage of fibrosis and reduction in capillary myocyte ratio in cases as compared to controls. There was no significant difference in arteriolar density. No significant association was observed between morphometric parameters and LVEF. Conclusion: Histomorphological changes in DCM are non-specific. Quantitation of histological parameters cannot be used to predict the disease progression as there was no significant correlation with LVEF. There is appreciable alteration in Collagen IV distribution in DCM owing to extracellular matrix alterations.