| 摘要 |
A parameter indicative of the condition of a cardiac valve is determined by monitoring blood flow and/or velocity in a vessel that is coupled to the cardiac valve or in a chamber adjacent to an artificial cardiac valve. One or more ultrasonic transducers are provided either in a wall or a cuff disposed about a cardiac vessel to monitor the parameter in regard to a natural or artificial cardiac valve, or in a support sewing ring of an artificial cardiac valve. A conformal array transducer or a tilted element is used to monitor fluid flow or velocity based on the effect of the blood on ultrasonic waves produced by the transducers. The conformal array transducer comprises a plurality of elements that are excited with an input signal provided by an implantable electronics circuit, producing ultrasonic waves. Transit time or Doppler measurements are made using an appropriate number of these transducers to determine either blood volumetric flow or velocity. Various implantable electronic circuits are disclosed that enable a transducer to be driven and to receive an ultrasonic signal indicative of the status of blood flow and thus, the condition of the cardiac valve. A radio frequency (RF) coil is coupled to an external coil. The external coil is connected to a power supply and monitoring console, conveying power to the ultrasonic transducers and receiving data signals that enable the condition of the cardiac valve to be determined. |
