Elevated collagen content in volume overload induced cardiac hypertrophy

This investigation was designed to determine if chronic volume overload is associated with altered collagen content of five regions of the myocardium. Five adult cats were subjected to a 6-week period of chronic volume overload induced by atrial septotomy and five untreated animals served as controls. Significant (P < 0.05) right ventricular hypertrophy was present as indicated by the right ventricular body weight ratio. For control animals this ratio was 0.68 ± 0.04 g/kg; for volume overloaded animals it was 0.83 ± 0.05 g/kg.) The collagen content was assessed by measuring the hydroxyproline content of the dried cardiac muscle. Right ventricular endocardium hydroxyproline in volume overloaded animals was significantly elevated above that in control animals (in the latter it was 5.30 ± 0.36 μg/mg; in the former it was 6.33 ± 0.18 μg/mg) while the epicardial collagen content was unchanged. Similarly, the amount of collagen found in the left ventricle was significantly increased in the endocardium and normal in the epicardium. Septal collagen concentration was unaltered in volume overloaded animals. This study demonstrated that alterations in cardiac muscle collagen concentration are associated with volume overload and that these cellular changes are nonuniform.