Opening and Closure Characteristics of Different Types of Stented Biological Valves

Abstract

Background: In an increasingly senescent population stented biological valves have regained renewed popularity because of the absence of anticoagulation, while the stented design allows for safe and easier implantation. Constructed bovine pericardial valves as well as valves with porcine cusps are used, both of which exhibit good clinical results although degeneration still appears. While clinical hemodynamic studies did not show particular differences between both valves types, the opening and closure behavior of native cusps and artificially constructed pericardial leaflets is different. It is unclear whether these phenomena account for differences in load and stress which may influence onset and course of degeneration. Material and Methods: Edwards Perimount (EP) and Medtronic Mosaic (MM) heart valves with diameters of 21 mm, 23 mm, and 25 mm were investigated in a pulse duplicator. Movements of the valves were visualized with a high-speed camera (1000 frames/sec). Mean transvalvular gradient (mm Hg), dissipated power (mW), and power transfer by stretching (mW), mean orifice area (mm²), opening time (ms), and closure time (ms) were analyzed in a range of cardiac outputs from 1.4 l/min to 6.3 l/min and 70 beats per minute. Results: Closure times were generally longer than opening times for both valve types. Opening time of EP valves was longer than opening time of the MM valves of the same size (EP23: 31.2 ± 2.5 ms; MM23: 12.7 ± 0.1 ms). With respect to closure times, however, there were no marked differences between all valves (EP23: 69.3 ± 2.0 ms; MM23: 63.2 ± 6.3 ms). Smaller sized Perimount valves exhibited lower mean transvalvular gradients than Mosaic valves of the same size (EP23: 7.21 ± 0.07 mm Hg; MM23: 10.5 ± 0.15 mm Hg). In larger sizes these differences diminished. Power transfer to the valve's structures was significantly enhanced in EP valves (EP23: 134 ± 1.3 mW; MM23: 64 ± 0.9 mW). Conclusions: While valves with constructed pericardium showed lower mean transvalvular gradients, particularly in the smaller sizes, this valve type exhibited alterations of movement performance in contrast to porcine valves. It can be speculated that constant power transfer to the valve's structures may result in an earlier degeneration because of the impact of the increased load and stress on the suspension apparatus of the constructed pericardial leaflets.

Key words

Bioprostheses - hydrodynamics - visualization - opening - closure

References

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