Effect of the sinus of Valsalva on the closing motion of bileaflet prosthetic heart valves

Conventional bileaflet prosthetic mechanical heart valves close passively w ith backflow. Naturally, the valve has problems associated with closure, su ch as backflow, water hammer effect, and fracture of the leaflet. On the ot her hand, in the case of the natural aortic valve, the vertex flow in the s inus of Valsalva pushes the leaflet to close, and the valve starts the clos ing motion earlier than the prosthetic valve as the forward flow decelerate s. This closing mechanism is thought to decrease backflow at valve closure. In this study, we propose a new bileaflet mechanical valve resembling a dr awbridge in shape, and the prototype valve tvas designed so that the leafle t closes with thr help of the vortex now in the sinus. The test valve was m ade of aluminum alloy, and its closing motion was compared to that of the C arboMedics (CM) valve. Both valves were driven by a computer controlled hyd raulic mock circulator and were photographed at 648 frames/s by a high spee d charge-coupled device (CCD) camera. Each frame of the valve motion image was analyzed with a personal computer. and the opening angles were measured . The flow rate was set as 5.0 L/min. The system was pulsed with 70 bpm, an d the systolic/diastolic ratio was 0.3. Glycerin water was used as the circ ulation fluid at room temperature, and polystyrene particles were used to v isualize the streamline. The model of the sinus of Valsalva was made of tra nsparent silicone rubber. As a result, high speed video analysis showed tha t the test valve started the closing motion 41 ms earlier than the CM valve , and streamline analysis showed that the test valve had a closing mechanis m similar to the natural one with the effect of vortex flow. The structure of the test valve was thought to be effective for soft closure and could so lve problems associated with closure.