[Quantitative ultrastructural findings of the myocardium in the failing heart. I. Aortic valve insufficiency (author's transl)].

Quantitative ultrastructural changes of the left ventricular (LV) myocardium and contractile function were studied in 9 symptomatic patients with severe aortic insufficiency (AI). The volume fractions of myofibrils, sarcoplasm, and mitochondria in myocardial cells were determined by electron microscopic morphometry in small LV tissue samples. Interstitial fibrosis was measured by light microscopic morphometry. Transmural biopsies of the LV free wall perfused by the left anterior descending coronary artery (LAD) were obtained during aortic valve replacement. Biopsies from the LAD-perfusion area of 10 surgical patients with coronary artery disease but moderate LAD-stenosis and normal regional motion of LAD-area were taken as controls for morphometric data. LV-function was analyzed from preoperative heart catheterization. In initial reproducibility studies of biopsy samples of 17 patients a sampling error for evaluation of myocardium was defined and differences exceeding 6.2% transmural fibrosis and 6.5% myofibrils were considered biologically significant differences. Patients with AI had higher LV end-diastolic volume (180 versus 77 ml/m2, p less than 0.001), and lower LV ejection fraction (51 versus 69%, p less than 0.001) than 10 control individuals. The volume fraction of myofibrils was lower in AI than in controls (44 versus 53%, p less than 0.01), and sarcoplasm was higher (33 versus 21%, p less than 0.01). Mitochondria and interstitial fibrosis did not differ between groups (p greater than 0.05). Thus reduction in the volume fraction of myofibrils was the major ultrastructural finding in LV biopsy samples of patients with heart failure due to aortic insufficiency.