Objectives: In the mitral annulus bi-leaflet mechanical valves can be oriented in two ways: the anatomical orientation with the hinge line parallel to a line through the commissures of the native valve (90 degrees). The influence of this orientation on the left ventricular spatial flow pattern and valve leaflet opening was investigated in pigs.
Methods: In 9 pigs a CarboMedics mitral valve prosthesis was implanted in the ) degree position and in 9 pigs in the 90 degree orientation. Two dimensional echocardiographic and color Doppler recordings were performed before surgery, immediately after surgery and after 6 weeks.
Results: In the native valve the diastolic flow pattern was characterized by a central inflow and backflow away from the apex along the left ventricular wall. In the 0 degree orientation a diastolic flow pattern with an asymmetrical inflow was observed, resulting from a greater extension of the jet along the lateral wall compared to the jet along the interventricular septum. Mid-diastolic back-flow away from the left ventricular apex was directed towards the valve prosthesis. In the 2-dimensional echocardiographic recordings the opening angle of both prosthetic leaflets was different showing a larger opening angle of the posterior leaflet. In the 90 degree orientation a diastolic flow pattern with paradoxical flow directions was recorded, that could only be explained in a 3-dimensional way: one inflow jet along the anterior wall, one inflow jet along the posterior wall and back-flow away from the apex sandwiched in between the two inflow jets. In this orientation the 2-dimensional echocardiographic recordings showed symmetrical opening of the two leaflets of the prosthesis.
Conclusions: The orientation of the CarboMedics bi-leaflet mechanical valve prosthesis in the mitral valve annulus determines the left ventricular spatial flow pattern. The flow pattern resulting from the 0 degree orientation, was associated with asymmetrical leaflet motion, while the 90 degree orientation flow pattern was associated with symmetrical leaflet motion. These findings may be of importance for prosthetic valve function as well as for left ventricular kinetics.