An in vivo analysis of ultrasonic signals created by closing bileaflet mechanical heart valves

Closing dynamics and frequency spectra of 183 mechanical heart valves (MHV) implanted in 162 patients were evaluated by analyzing ultrasonic signals created during valve closing. Closing sounds were recorded with a system responsive to frequencies up to 400 kHz. All bileaflet MHV showed evidence of asynchronous leaflet closure that was independent of valve characteristics, but depended upon implant site and patient position. The time interval between leaflet impacts tended to remain stable over time in individual patients. Most of the closing sound energy was in the ultrasonic range with frequency characteristics that were independent of valve properties. The presence of these high energy ultrasonic signals has allowed the authors to develop a real-time system for the audio evaluation of MHV. Results obtained with this system have shown that both closing dynamics and frequency spectra of closing sounds of bileaflet MHV depend primarily upon local environment