Reduced volume fraction of myofibrils in myocardium of patients with decompensated pressure overload
Schwarz, F.; Schaper, J.; Kittstein, D.; Flameng, W.; Walter, P.; Schaper, W.
Circulation 63(6): 1299-1304
1981
ISSN/ISBN: 0009-7322 PMID: 7226475 Document Number: 181496
The relation between quantitative ultrastructural changes of the left ventricular (LV) myocardium and contractile function was studied in patients with chronic aortic stenosis (AS). The volume fractions of myofibrils, sarcoplasm and mitochondria in myocardial cells were determined by EM morphometry in small LV tissue samples of 19 patients with AS. Interstitial fibrosis was measured by light microscopic morphometry. Transmural biopsies of the LV free wall perfused by the anterior descending branch of the left anterior descending coronary artery (LAD) were obtained during aortic valve replacement. LV function was analyzed from preoperative right- and left-heart catheterization and angiography. Group 1 consisted of 7 patients with ejection fractions (EF) > 55% and mean left atrial pressure (LAP) < 15 mm Hg. Group 2 consisted of 12 patients with EF < 55% and mean LAP > 15 mm Hg. Patients in group 1 had lower LV end-diastolic volume (91.9 vs. 145.3 ml/m2, P < 0.05) and lower LV muscle mass (148.3 vs. 199.8 g/m2, P < 0.05) than patients in group 2. The volume fraction of myofibrils was higher in group 1 than in group 2 (48.4 vs. 42.1%, P < 0.05), while volume fractions of sarcoplasm (31.7 vs. 36.0%) and mitochondria (20.9 vs. 22.0%) were comparable (P > 0.05). Interstitial myocardial fibrosis did not differ between groups (16.3 vs. 14.7%, P > 0.05). Biopsies from the area perfused by the LAD in 10 additional surgical patients who had coronary artery disease with moderate LAD stenosis and normal wall motion in the area of LV free wall perfused by the LAD were taken as controls for morphometric data. No significant difference of ultrastructural data was found between group 1 and controls. The volume fraction of myofibrils was lower in group 2 than in controls (42.1 vs. 52.9%, P < 0.001) and the volume fraction of sarcoplasm was higher (36.0 vs. 21.1%, P < 0.001). Mitochondria and interstitial fibrosis did not differ in group 2 and controls (P > 0.05). Intracellular reduction in the volume fraction of myofibrils was the major morphologic finding in LV biopsy samples of patients with decompensated pressure overload.