CHRONIC HIBERNATING MYOCARDIUM - INTERSTITIAL CHANGES

Chronic left ventricular dysfunctional but viable myocardium of patien ts with chronic hibernation is characterized by structural changes, wh ich consist of depletion of contractile elements, accumulation of glyc ogen, nuclear chromatin dispersion, depletion of sarcoplasmic reticulu m and mitochondrial shape changes. These alterations are not reminisce nt of degeneration but are interpreted as de-differentiation of the ca rdiomyocytes. The above mentioned changes are accompanied by a marked increase in the interstitial space. The present study describes qualit ative and quantitative changes in the cellular and non-cellular Compar tments of the interstitial space. In chronic hibernating myocardial se gments the increased extracellular matrix is filled with large amounts of type I collagen, type III collagen and fibronectin. An increase in the number of vimentin-positive cells (endothelial cells and fibrobla sts) compared with normal myocardium is seen throughout the extracellu lar matrix. The increase in interstitial tissue is considered as one o f the main determinants responsible for the lack of immediate recovery of contractile function after restoration of the blood flow to the af fected myocardial segments of patients with chronic left ventricular d ysfunction.