Aim of the study: Several studies have shown the inferior performance of small prostheses in the narrow aortic root. However, modern low-profile mechanical prostheses have improved hemodynamic performance characteristics. By measuring the transprosthetic pressure gradient in vivo, we were able to characterize the hemodynamic features of two prostheses: the ATS Medical (ATS) and the Medtronic Hall (MH) valves.
Methods: From October 1994 to April 2002, 113 patients received an aortic valve replacement (AVR) with either an ATS or a MH valve. The transprosthetic pressure gradients, calculated from a simplified Bernoulli equation during immediate postoperative Doppler echocardiographic examination, were compared for differently sized prostheses with respect to body surface area (BSA).
Results: The mean pressure gradients and the mean BSAs were: 27.8 +/- 14.8 mm Hg and 1.50 +/- 0.10 m(2) in ATS 19 mm (n = 7), 20.4 +/- 8.5 mm Hg and 1.54 +/- 0.11 m(2) in ATS 21 mm (n = 22), 13.0 +/- 5.7 mm Hg, 1.70 +/- 0.13 m(2) in ATS 23 mm (n = 22), 10.9 +/- 3.5 mm Hg and 1.81 +/ -0.16 m(2) in ATS 25 mm (n = 19), 9.3 +/- 0.6 mm Hg and 1.72 +/- 0.17 m(2) in ATS 27 mm (n = 4), 13.5 +/- 6.5 mm Hg and 1.54 +/- 0.13 m(2) in MH 20 mm (n = 9), 10.9 +/- 4.7 mm Hg and 1.64 +/- 0.15 m(2) in MH 22 mm (n = 22), 9.3 +/- 3.1 mm Hg and 1.72 +/- 0.12 m(2) in MH 24 mm (n = 7).
Conclusions: With the exception of the ATS 19-mm valve, the variously sized prostheses have acceptable transprosthetic pressure gradient measurements. In addition, even-sized MH valves (20 and 22 mm) with a thinner sewing cuff showed better hemodynamic performances than similarly sized ATS valves.