动力性主动脉瓣实验研究

Experimental study on a new device for left ventricular assist: dynamic aortic valve

目的 “动力性主动脉瓣”是先前提出的一种左心辅助的新设想 ,该实验试图进一步证实该设想的可行性。方法 “动力性主动脉瓣”的基本设计思想是将一推进叶轮植入到主动脉瓣的位置 ,由体外提供的电磁场驱动 ,根据输入功率的不同分别发挥机械性瓣膜或辅助性血泵两种不同的功能。该装置实际上采用了轴流泵和机械性心脏瓣膜的结构和工作原理。由固定于磁性转子上的推进叶轮和起支承作用的刚性支架笼组成。磁性转子和叶轮构成“转子—叶轮体” ,此“转子 -叶轮体”由位于动脉壁外的交变磁场提供动力 ,但磁场源也可设置于体外发挥作用。实验对先前的装置进行了较大的改进 ,制作了新的样机。样机尺寸 :外径为 2 2mm ,长 2 0mm。叶轮直径 18mm ,为 3叶式。转子由永磁材料制成 ,直径 8mm ,长 15mm。驱动“转子 -叶轮体”旋转的交变磁场由一旋转磁体产生 ,于距“转子—叶轮体”15mm处平行放置。结果 应用体外模拟循环回路对以上动力瓣模型的流体力学特性进行了测试。在最大的功率输出条件下 ,流量可达到 5L/min ,所克服的后负荷压强为 6 .6 5kPa(5 0mmHg)。在每分钟12 0 0 0转的条件下 ,动力瓣可维持的最高压强差为 10 .6 4kPa(80mmHg)。 结论 动力瓣特性较前已有很大提高 ,表明动力瓣设想的可行性 ,提示进一?

Objective Prototype of a novel device, previously named 'Dynamic Aortic Valve (DAV)', for left ventricular assistance was fabricated and tested to demonstrate its feasibility. Methods An impeller similar to an airscrew is to be placed in the position of aortic valve .The impeller is held by a cylindrical supporting cage locating in the lumen of arising aorta by attaching to the valve annulus via a sewing ring. A permanent magnetic rotor is fitted into the cage and fixed to the impeller to form a “rotor-impeller”. The supporting cage would port the aortic wall thus prevent the rotor from connecting to the wall, allowing the rotor to whirl freely. The alternating magnetic field generated by a extracorporeal device would drive the rotor to rotate and the axial flow of blood from ventricular to the aorta would be produced, resulting in the reduction of the ventricular load. Based on such hypotheses, A prototype of “DAV” was fabricated and tested in a mock circuit. In the present stage, The rotor is 8 mm in diameter and 15 mm in length, the impeller has 3 vanes with a diameter of 18 mm. The supporting cage is 22 mm in outer diameter and 20 mm in length. The alternating magnetic field turning the“'rotor-impeller” was produced by a rotating magnet placed side by side with the “rotor-impeller” at a distance of 15 mm.Result The prototype was fitted into a tube, simulating the aorta, full of water solution of glycerol. When actuated by magnetic force, the “rotor-impeller” of DAV started to rotate, producing a pressure difference and liquid flow in the tube. The flow rate or pressure difference proportioned to rotational speed. At the state of maximal output of hydraulic power, the flow rate reaches 5 L/min against a afterload of 6.65 kPa.Conclusion The maximal pressure differential maintained by the DAV prototype at 12 000 r/min is 10.64 kPa. The results demonstrated the feasibility of the concept of DAV, suggesting that further researches on this concept are justifiable.