Histochemically determinable changes in cardiac insufficiency and their functional significance.

Chronic cardiac insufficiency can be produced by a variety of causes which may be partly determined by means of macroscopic, histological and electron microscopic investigations. By using quantitative histochemical methods, changes of substances in the myocardium can be observed indicating myocardial insufficiency and giving an explanation of its cause. Hypertrophied hearts without insufficiency show cardiac muscle fibres having increased in width, volume and dry weight up to a maximum value which will not be exceeded even in further progressing cardiac hypertrophy. The biochemically determined amount of collagen increases significantly with the growing weight of the myocardium. Both the myocardial amount of DNA and the amount of myoglobin, correlated with the width of the fibres, have also increased. The heart muscle nuclei showed a polyploidization which is also correlated with the weight of the myocardium. In insufficient hearts suffering from myocardial hypertrophy, the increase of the total DNA content is significantly decreased as compared to non-insufficient hearts. The mean ploidy level is increased in case of lower weights of the myocardium and decreased in higher weights in comparison to non-insufficient hearts of the same weight. In insufficient hearts a more significantly increased amount of the connective tissue cells is observed than in the case of cardiac hypertrophy alone. In contrast to this, the increase of the heart muscle cells is significantly reduced. A lack of contractile proteins, decreased DNA synthesis, increased fibrozation and, in particular, the reduced number of cardiac muscle cells must be considered as essential factors for cardiac insufficiency.