Endomyocardial fibrosis is associated with selective deposition of type I collagen

Endomyocardial fibrosis is a distinct form of heart disease leading to restrictive ventricular filling and cardiac failure. The disease is characterized by a marked thickening of the endocardium due to the deposition of dense fibrous tissue composed of wavy bundles of collagen. Changes in collagen composition and an abnormal increase in its concentration result in a stiffer myocardium and ventricular diastolic dysfunction. The nature of cardiac collagens and the relative proportions of collagen types in endomyocardial fibrosis have not been documented in the literature.

This study analyzed collagen composition in the cardiac tissues of 13 patients with endomyocardial fibrosis and 6 individuals who were the victims of traffic accidents or suicidal deaths and did not have any heart disease. We estimated the relative proportions of types I and III collagen after pepsin digestion of the tissue and separation of the emerging peptides by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The mean type I:III collagen ratio was 0.51+/-0.06 in normal individuals, and 0.93+/-0.43 in patients with endomyocardial fibrosis (p<0.05). The alteration in the type I:III collagen ratio was due to a disproportionate increase in type I collagen.

The results indicate that a selective increase in type I collagen may contribute to the impaired diastolic distension of the ventricles in patients with endomyocardial fibrosis.