Comparison of exercise hemodynamics among nonstented aortic bioprostheses,mechanical valves, and normal native aortic valves

Background: While aortic valve prostheses are known to perform well at rest , few studies have examined them under stress. We compared stress hemodynam ics of mechanical valves and nonstented porcine valves in the aortic positi on to that of normal native aortic valves. Methods: Dobutamine echocardiogr aphy was used to assess mean and peak gradients and effective orifice area index (EOAI) at rest and exercise in patients with the Toronto Stentless Po rcine Valve (SPV) (n = 13, mean implant size 25.7 mm), Sorin Bicarbon mecha nical valve (SOR) (n = 11, mean implant size 24.5 mm), and patients with no rmal native aortic valves (NOR) (n = 10). Dobutamine infusion was started a t 5 mu/kg per minute, and increased by increments of 5 mu/kg per minute unt il the target heart rate was achieved or until a maximal dose of 40 mu/kg p er minute. Results: At rest and exercise, respectively, cardiac output (L/m in) was 5.2 and 10.4 for Toronto SPV; 7.4 and 13.5 for SOR; and 4.6 and 11. 2 for NOR. Measured EOAI (cm(2)) was 1.1 +/- 0.2 and 1.15 +/- 0.2 for TORON TO SPV; 1.60 +/- 0.3 and 1.58 +/- 0.3 for SOR; and 1.45 +/- 0.2 and 1.46 +/ - 0.2 for NOR. Mean gradients (mmHg) were 5.48 +/- 1.1 and 5.83 +/- 0.9 for TORONTO SPV; 5.26 +/- 0.8 and 11.3 +/- 1.8 for SOR; and 1.54 +/- 0.4 and 2 .18 +/- 0.7 for NOR. Peak gradients (mmHg) were 11.9 +/- 2.0 and 21.0 +/- 3 .7 for TORONTO SPV; 10.79 +/- 1.7 and 25.9 +/- 3.4 for SOR; and 2.38 +/- 0. 9 and 6.1 +/- 2.3 for NOR. Conclusions: Although the mechanical group (SOR) had larger measured EOAI, the greater increase in gradients with exercise in this group suggests that the TORONTO SPV is less obstructive to flow.