Exercise hemodynamics of aortic prostheses: comparison between stentless bioprostheses and mechanical valves

Background. Nonstented bioprostheses have been associated with lower resting gradients than stented bioprostheses or mechanical valves. We compared the hemodynamic performance of nonstented bioprostheses and mechanical valves with normal native aortic valves at rest and exercise. Methods. Dobutamine echocardiography was used to assess gradients and effective orifice area index at rest and exercise in patients with the Toronto stentless porcine valve (TSPV; N = 13; mean implant size 25.7 mm), Medtronic Freestyle (FR; N = 11; mean implant size 23.9 mm), Sorin Bicarbon (SOR; N = 11; mean implant size 24.5 mm), St. Jude Medical (SJM; N = 10; mean implant size 21.3 mm), and normal native aortic valves (NOR; N = 10). Results. All groups demonstrated a major rise in cardiac output at maximal dobutamine infusion. At rest and exercise, respectively, mean gradients were 5.48 ± 1.1 mm Hg and 5.83 ± 0.9 mm Hg for TSPV, 5.68 ± 1.2 mm Hg and 7.50 ± 1.7 mm Hg for FR, 10.29 ± 1.4 mm Hg and 20.78 ± 2.7 mm Hg for SJM, 5.26 ± 0.8 mm Hg and 11.1 ± 1.8 mm Hg for SOR, and 1.54 ± 0.4 mm Hg and 2.18 ± 0.7 mm Hg for NOR. In comparison with normal valves, both stentless groups showed no change in mean gradient at exercise, whereas both mechanical groups showed an increase in gradient at exercise (p < 0.04). Conclusions. Stentless valves behave similarly to normal aortic valves in that there is almost no increase in gradient at exercise. Both mechanical valve groups showed increased gradients at exercise, suggesting that these valves obstruct blood flow. Our data add further evidence that stentless valves are hemodynamically superior to mechanical valves in the aortic position.