Hemodynamics of the mitral valve under edge-to-edge repair: an in vitro steady flow study

Edge-to-edge repair (ETER) is a mitral valve repair technique that restores valvular competence by suturing together the free edges of two leaflets. This repair technique alters mitral valve inflow and thus left ventricle hemodynamics during diastole. Our objective was to investigate fluid mechanics immediately downstream of the mitral valve under ETER during diastole. Fresh porcine mitral valves of the annulus size M32 with chordae removed were installed into a steady flow loop simulating a peak diastolic inflow through the mitral valve. Digital particle image velocimetry was used to measure the velocity field immediately downstream of the mitral valve under normal and ETER conditions. First, to study the suture length effect, suture was applied in the central position of the leaflet edge with suture lengths of 3 mm, 6 mm, and 9 mm, respectively. Then, 3 mm suture was set in the central, lateral, and commissural positions of the leaflet edge to study the suture position effect. Flow rate was 15 l/min. Velocity, Reynolds shear stress (RSS), and effective orifice area were assessed. A total of five mitral valves were tested. The normal mitral valve without the ETER had one jet downstream of the valve, but the mitral valve with the central or lateral sutures under the ETER had two jets downstream of the valve with a recirculation region downstream of the suture. The maximum velocity, the maximum RSS in the jets, the pressure drop across the mitral valve, and the jet deflection angle increased with the increase in suture length in the central position. When the suture position effect was investigated with the 3 mm suture, the maximum velocity, the maximum RSS, and the pressure drop across the valve in the central suture position were greater than those of the lateral and the commissural suture positions. The lateral suture demonstrated major and minor jets with the greater maximum velocity and maximum RSS in the major jet. When the suture was in the commissural position, the flow field downstream of the mitral valve was similar to that of the normal mitral valve without the ETER. The effective orifice area was smallest when the suture was applied in the central position as compared with other suture positions. Both suture length and position have an important impact on fluid mechanics downstream of the mitral valve under the ETER in terms of flow pattern, maximum velocity, and RSS distribution. The altered hemodynamics of the mitral valve and thus of the left ventricle by the ETER may change mitral valve and left ventricle function.