Abstract
Doppler echocardiography was performed in 93 patients with a normal functioning mitral prosthetic valve in order to determine normal values for commonly used prosthetic valves. This included patients with Medtronic-Hall (n =23), St. Jude (n = 57) and Bioprosthetic valves (n = 13). Peak and mean pressure gradients across the prostheses were measured using the simplified Bernoulli equation. The prosthetic valve area (PYA) was calculated by the pressure halftime method. The St. Jude valve had the lowest peak velocity (1.47 ± 0.25 m/s,range 1.03-2.05 m/s) and peak gradient (8.7 ± 3.2 mmHg, range 4.2-16.8) and the third best mean gradient (2.8 ± 1.1 mm Hg, range 1.0-5.8 mm Hg) after the Medtronic-Hall valve (2.3 ±1.1 mm Hg, range 1.1-6.5 mm Hg) and the Bioprosthetic valves (2.8 ± 0.8 mm Hg, range 1.8-4.7 mm Hg). No statistical significance was observed between the different groups for maximal velocity and peak pressure gradient (H = 2.20; p = 0.33). The lowest pressure half-time and so the highest PVA were found for the Medtronic-Hall valve (81 ±25 ms, range 42-160 ms, and 2.9 ± 0.9 cm2, range 1.4-5.3 cm2) compared to the St. Jude valve (93 ± 21 ms, range 46-177 ms and 2.5 ± 0.6 cm^2, range 1.2-4.8 cm^2)and the Bioprosthetic valve (107 ± 31 ms, range 63-164 ms, and 2.2 ±0.7 cm2, range 1.4-3.5 cm^2). Only slight statistical differences were found for mean velocity and mean pressure gradient (H = 7.71 ; p < 0.05) and for pressure half-time and PVA (H = 9.39; p < 0.01). For all practical purposes there are no physiologically significant differences at the present.