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Anatomy of aortic heart valve leaflets: the influence of glutaraldehyde fixation on function.

The basic function of the aortic valve is reviewed from an engineering perspective. Critical examination of the leaflet morphology can yield insights into how the leaflets function and transmit load to the aortic wall. From an understanding of both the structure and the function it is possible to estimate the impact of stent mounting and glutaraldehyde fixation. It is shown from simple engineering considerations that the major stresses are in the circumferential direction and that the radial components must be very small. Similarly, the largest strains are radial to facilitate the formation of a large coaptation area, while the circumferential strains are explained by the extension to the crimped collagen fibres. Glutaraldehyde fixation can greatly modify the mechanics of the leaflets but this can be minimized by fixation with no pressure differential across the closed valve. Zero-pressure-fixed leaflets are much softer and extensible than those from valves fixed under even low back-pressure (2-4 mmHg). This difference translates into a mode of valve function that more closely approximates that of the native aortic valve.