Ultrastructural and morphometric study of the human heart muscle cell in acute coronary insufficiency

In 13 patients with acute coronary insufficiency (intermediate syndrome, postinfarction angina, and progressive angina), samples of the ischemic area of the myocardium were studied with the electron microscope and by morphometric methods in order to describe quantitatively the mitochondrial population. Three indices were measured: the fractional volume of the mitochondrial compartment of the cytoplasm, the number of mitochondria per unit volume of heart tissue, and the average individual mitochondrial volume. As a control, the same study was performed on samples obtained from patients with chronic coronary insufficiency and mitral stenosis. In all the ischemic hearts the most conspicuous ultrastructural modification of the muscle cells consisted in an irregular distribution of the mitochondriranules. Generally, odd shaped mitochondria were found. The modifications were not diffuse, and almost normal heart muscle cells were seen alongside deeply altered ones. In addition a definite decrease in the fractional volume of the mitochondrial compartment was found, which was apparently due to a decrease in the number of mitochondria per unit volume of cytoplasm. The average individual mitochondrial volume was similar in acute coronary insufficiency and in the control cases. On the basis of this evidence it is postulated that in sublethal ischemia definite ultrastructural modifications of the heart muscle cells are associated with a decrease in the number of mitochondria per unit volume of cytoplasm.