Characteristic resistance curves of aortic valve substitutes facilitate individualized decision for a particular type

Biological valves exhibit characteristic curves (CC) regarding transvalvular gradient, resistance, and effective orifice area when correlated with a physiological cardiac output range (CO). The slope of the curve of transvalvular resistance over a typical CO range characterizes the clinical performance of the valve. These information may support an individualized decision towards the most adequate valve type.

In an extracorporeal mock circuit two types of stented biological aortic valves (constructed pericardial valves, Edwards Perimount: EP; porcine cusp valves, Medtronic Mosaic: MM) of 21, 23, and 25 mm were investigated. Mean transvalvular gradient was measured over a range of 1.9 to 7.2l/min CO at a simulated heart rate of 70 beats/min. Transvalvular resistance was calculated and presented as characteristic curves in a log-log-plot against cardiac output.

EP valves of all sizes demonstrated low slopes (resistance range; slope: 21 mm: 53-79 dynes s cm(-5); 0.29; 23 mm: 44-56 dynes s cm(-5); 0.12; 25 mm: 38-45 dynes s cm(-5); 0.12) while MM valves exhibited steep slopes (resistance range; slope: 21 mm: 46-169 dynes s cm(-5); 0.97; 23 mm: 36- -146 dynes s cm(-5); 0.95; 25 mm: 27-64 dynes s cm(-5); 0.68).

While constructed pericardial valves demonstrate sufficient hemodynamic performance especially in the higher CO range porcine cusp valves exhibited minor resistance in the lower CO range. Patients who exercise regularly may therefore profit from a pericardial valve while patients with a small body surface area and little exercise who therefore remain in the lower CO range may be adequately treated with a porcine cusp valve.