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Acoustic Evaluation of Prosthetic Cardiac Valve Performance
A new non-invasive technique, octave band analysis has been utilized for measuring objectively the sound level energy in dB and cutoff frequency in Hz of prosthetic valve sounds in 100 patients. Frequency profiles (dB vs. frequency) have been plotted for normally functional Starr-Edwards silastic and metal ball valves, Cross-Jones and Beall disc valves and Bjork flap valves. For example, a normal aortic metal ball prosthesis showed a frequency cutoff at 16,000 Hz. The same type of aortic prosthesis with massive thrombosis showed a cutoff frequency of 500 Hz. Four cracked and deformed silastic aortic balls demonstrated considerable reduction in dB energy level as well as cutoff frequency of 250 Hz. This technique appears to be very useful for the detection of prosthetic valve malfunction.
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