Aortic orifice area

Fixed bovine pericardial tissue is also used to construct heart valves in which design characteristics such as orifice area, valve height, and degree of coaptation can be specified and controlled. Thus, the geometry and flow dynamics past pericardial prostheses mimic those of the natural human aortic valves more closely. Due to the low profile design of pericardial prostheses and increased orifice area, these valves are less stenotic compared to porcine bioprostheses, especially in smaller sizes [Chandran et al., 1984]. In the currently available bioprostheses, the stents are constructed from polypropylene, Acetol homopolymer or copolymer, Elgiloy wire, or titanium. A stainless steel radiopaque marker is also introduced to visualize the valve in vivo. Other biomateriaU, which have been employed in making the bioprostheses, include fascia lata tissue as well as human duramater tissue. The former was prone to deterioration and hence unsuitable for bioprosthetic apphcation, while the latter lacked commercial avahabihty. 

Recent investigations also suggest that direct plani-metric measurement of the aortic valve orifice area during diastole area provides useful additional information on the presence and severity of aortic valve regurgitation (Fig. 19.5). In addition, MDCT also provides important morphologic information on the aortic valve (bicuspid vs. tricuspid valve severity of calcifications) and enables an exact three-dimensional visuahzation of the aortic root, including precise measurements of the aortic root diameters, which is of particular interest for... 

The measurement of valve orifice area (most often applied for aortic valve disease) can be applied to both techniques, CT and MW. Based on systolic images within the valvular plane, the outline of the valve orifice can be traced to evaluate the orifice area. The results of both methods show close correlation in comparison to echocardiography (Feuchtner et al. 2006b, 2007 Pouleur et al. 2007b). The measurement of the residual opening area in the setting of valve closure has also been used in CT imaging in order to assess and... 

TABLE 77.1 Effective Orifice Areas of Different Prosthetic Aortic Valve Designs... 

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