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 hemodynamics of mechanical valves and nonstented porcine valves in the aortic position to that of normal native aortic valves. METHODS: Dobutamine echocardiography was used to assess mean and peak gradients and effective orifice area index (EOAI) at rest and exercise in patients with the Toronto Stentless Porcine Valve (SPV) (n = 13, mean implant size 25.7 mm), Sorin Bicarbon mechanical valve (SOR) (n = 11, mean implant size 24.5 mm), and patients with normal native aortic valves (NOR) (n = 10). Dobutamine infusion was started at 5 micron/kg per minute, and increased by increments of 5 micron/kg per minute until the target heart rate was achieved or until a maximal dose of 40 micron/kg per minute. RESULTS: At rest and exercise, respectively, cardiac output (L/min) 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 (cm2) was 1.1+/-0.2 and 1.15+/-0.2 for TORONTO 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.