Hemodynamic Comparison of Two Models of Bioprosthetic Mitral Valves Under Standardized In Vitro Conditions

Background and objectives Mitral valve replacement may be considered in patients with mitral valve disease when durable repair is not feasible. In recent decades, an important shift toward the use of bioprostheses for mitral valve replacement was observed and the surgical valve design has undergone several iterations to optimize the prosthesis hemodynamic performance. The objective of this study was to compare the hemodynamic performance of the stented porcine (EPIC Plus) versus the stented bovine pericardial (MITRIS) bioprostheses under standardized in vitro conditions. Methods Three MITRIS 27 mm and three EPIC Plus 29 mm, which are equivalent in terms of actual sizing (ie, fit into the same mitral annulus size of 38 mm), were tested in vitro in a double activation left heart duplicator system including anatomically shaped, deformable silicone moldings of left heart cavities and aorta. The valves were tested under several standardized hemodynamic conditions: heart rate: 70 and 120 bpm, mean aortic pressure: 100 and 160 mm Hg, stroke volume: 30, 70, and 100 mL. Mean mitral transprosthetic pressure gradients (mTPGs) and effective orifice areas (EOAs) were measured by continuous-wave Doppler and the geometric orifice areas (GOAs) were obtained using high speed, en-face, imaging. Results For normal heart rate (70 bpm) and normal mean aortic pressure (100 mm Hg), the mTPGs were similar (1.76 ± 0.10 vs 1.44 ± 0.09 mm Hg) in low-flow conditions, but lower ( P ≤ .001) in normal (2.48 ± 0.13 vs 3.72 ± 0.20 mm Hg) and high flow (4.12 ± 0.19 vs 5.82 ± 0.32 mm Hg) in MITRIS versus EPIC Plus valves. EOAs were larger in MITRIS versus EPIC Plus valves for all, except low flow, conditions (low: 1.75 ± 0.06 vs 1.87 ± 0.05, normal: 2.73 ± 0.09 vs 2.16 ± 0.12, and high flow: 3.02 ± 0.07 vs 2.54 ± 0.21 cm 2 , all P ≤ .001). GOAs were also larger in MITRIS versus EPIC Plus valves (low: 2.57 ± 0.07 vs 2.50 ± 0.08, normal: 3.07 ± 0.07 vs 2.87 ± 0.08, and high flow: 3.16 ± 0.07 vs 3.02 ± 0.10 cm 2 , all P ≤ .001). The two bioprosthetic valves had regurgitant fraction (RF) < 5% without statistical differences between flow conditions. Conclusions This study demonstrates excellent valve hemodynamic performance for these two types of mitral bioprosthetic valves. However, the overall hemodynamic performances were superior with the MITRIS valve compared to the EPIC Plus valve for all flow conditions.