Vibrational analysis of bioprosthetic heart valve leaflets using numerical models: effects of leaflet stiffening, calcification, and perforation.

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Abstract
The fundamental natural frequency of the closed cusps of porcine bioprosthetic valves, fabricated from the normal leaflets of pig aortic valves, was estimated using a finite element model. Both normal and stiffened leaflets were considered in the vibrational analysis. The effects of conditions that simulated degeneration, such as stiffening, central perforation, a tear, calcium deposits in the commissural attachments, and combinations of these were determined. The primary frequency of vibration of the normal leaflets was within the range of the dominant frequency of the heart sounds determined clinically by spectral analysis of the recorded phonocardiogram. If only one leaflet was stiffened or calcified, there was only a marginal change of frequency. With stiffening and calcification of the commissures of all 3 leaflets, the frequency of vibration increased. Introduction of a tear in a single leaflet of a stiffened and calcified valve markedly reduced the fundamental frequency. In view of the relation between the frequency content of heart sounds and the frequency of valve vibration, this mathematical simulation establishes a possible basis for the observation of a varying dominant frequency of heart sounds in patients with bioprosthetic valves that are in the process of degenerating.