ABSTRACT
Atherosclerosis is the most severe problem in the high-pressure systemic circulation and similar changes also occur in the high-pressure loading valve. This study was designed to test the hypothesis that early atherosclerosis, induced by a high cholesterol diet in rabbits, is characterized by significant ultrastructural change in the elastic laminae of the aortic valve. However, it is not known whether this process is also taking place in the cardiac valve at the early stage of atherosclerosis. Animals were fed either a high cholesterol diet (n = 5) or a control diet (n = 5) for 10-12 weeks. Histologic analysis demonstrated that subendothelial thickening and foam-cell infiltration were evident in the arterialis of aortic valves. Confocal microscopy revealed an altered pattern characterized by fragmentation and disorganization of the arterialis elastic laminae of hypercholesterolemic valves. Computerized digital analysis of the images obtained by confocal scanning microscopy demonstrated that compared to normal valves, the arterialis elastic laminae of hypercholesterolemic valves decreased in percentage of their elastin content (29.03 +/- 1.10% vs. 42.94 +/- 1.35%, p = 0.023). Immunohistochemical staining for matrix metalloproteinase-3 (MMP-3) revealed MMP-3 immunoreactivity was increased in hypercholesterolemic valves, predominantly in the arterialis. This study demonstrated that early atherosclerosis, induced by a high cholesterol diet in rabbits, is characterized by significant ultrastructural change in the elastic laminae of the aortic valve. The arterialis endothelium of the aortic valve may be a more atherosclerosis-prone area compared with the ventricularis. The presence of ultrastructural defect in the elastic laminae may play a role in chronic degenerative change and a resultant valvular dysfunction.
Subject(s)
Male , Rabbits , Animals , Aortic Valve/ultrastructure , Elastic Tissue/ultrastructure , Hypercholesterolemia/pathology , Microscopy, Confocal , Matrix Metalloproteinase 3/metabolismABSTRACT
PURPOSE--To establish the range of normal values by Doppler echocardiography of the parameters inherent to the hemodynamic performance of the Lillehei-Kaster (LK) and Medtronic Hall (MH) prosthetic valves (V), in the 23 mm (LKV-16, MHV-23) and 25 mm (LKV-18, MHV-25) outer diameter valves, in the aortic position. METHODS--Doppler echocardiography was performed in 32 asymptomatic patients, with normally functioning prosthetic aortic valves (8 of each type). RESULTS--The peak velocity of aortic jet was 3.13 +/- 0.46 m/sec for the LKV-16, 2.76 +/- 0.31 m/sec for the MHV-23, 2.82 +/- 0.48 m/sec for the LKV-18 and 2.43 +/- 0.36 m/sec for the MHV-25. The maximal pressure gradient was 39.84 +/- 12.05 mmHg for the LKV-16, 30.70 +/- 6.80 mmHg for the MHV-23, 32.60 +/- 10.75 mmHg for the LKV-18 and 24.11 +/- 6.70 mmHg for the MHV-25. The mean pressure gradient was 24.25 +/- 7.09 mmHg for the LKV-16, 18.50 +/- 4.41 mmHg for the MHV-23, 18.21 +/- 6.95 mmHg for the LKV-18 and 13.57 +/- 4.17 mmHg for the MHV-25. The valve effective orifice area, considering the left ventricle outflow area determined by two-dimensional echocardiography in the continuity equation, was 0.62 +/- 0.13 cm2 for the LKV-16, 1.05 +/- 0.21 cm2 for the MHV-23, 0.98 +/- 0.22 cm2 for the LKV-18 and 1.36 +/- 0.36 cm2 for the MHV-25. Considering the left ventricle outflow area equivalent to the valve sewing ring area, the valve effective orifice area was 1.40 +/- 0.23 cm2 for the LKV-16, 1.65 +/- 0.19 cm2 for the MHV-23, 1.91 +/- 0.43 cm2 for the LKV-18 and 2.37 +/- 0.56 cm2 for the MHV-25. The Doppler velocity index was 0.34 +/- 0.05 for the LKV-16, 0.40 +/- 0.04 for the MHV-23, 0.39 +/- 0.09 for the LKV-18 and 0.49 +/- 0.11 for the MHV-25. CONCLUSION--Significant hemodynamic performance superiority of the MHV over the LKV was registered, indicating that the small LKV (LKV-16 or smaller) should be avoided