[Light and electron microscopy findings in early and late stages of heart failure. Studies of endomyocardial biopsies of patients with latent (LCM) and dilated (DCM) cardiomyopathy].

Right-ventricular myocardial biopsies were obtained from 28 patients with LCM (EF 72 +/- 10.4%) and 36 patients with DCM of different degrees (EF 45 +/- 15%). Using paraffin sections and electron micrographs, 16 structural variables were semiquantitatively evaluated. Hypertrophy of myofibres, and nuclear and mitochondrial alterations were significantly more pronounced in patients with DCM. A score of 9 selected variables was found to be significantly higher in the DCM-group as compared with the LCM-group. The diameter of the myofibres was significantly thicker in DCM (17.5 +/- 2.2 microns) than in LCM (14.6 +/- 0.95 microns), but no significant difference of the volume density of myofibrils and of mitochondria could be determined. In the myocytes of DCM the mitochondria were significantly smaller than in LCM. The EF correlates with the myofibre thickness, with the semiquantitative score, and with the size of the mitochondria, but no significant correlation was seen with the volume density of myofibrils or mitochondria. The study has shown: At present no alterations in myocardial biopsies are known to be diagnostic for LCM or DCM. The findings support the concept of a diffuse myocardial disease in LCM. Only one patient out of 28 exhibited a myocardium without any pathologic changes. There is no evidence for small vessel disease in LCM. From the morphological point of view DCM and LCM are different only in quantity, but not in quality of their structural alterations.(ABSTRACT TRUNCATED AT 250 WORDS)