Diagnostic Value of Intracardiac Phonocardiography in Some Complicated Cardiac Problems *

Feruglio, G A; Gunton, R. W.; Sreenivasan, Akkaya; Heimbecker, R. O.

doi:10.1097/00000658-196007000-00005

Cited by 5 publications

(1 citation statement)

References 5 publications

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“…Catheter-mounted phonocardiographic transducers were first introduced in the 1950s [l]. Early studies were useful in establishing the risk associated with passing sound catheters and identifying sites of greatest intensity of heart sounds and murmurs [6][7][8]12,13]. Four types of systems have been used in the catheterization laboratory to record intravascular sounds: 1) condenser microphones, 2 ) piezoelectric transducers, 3) fluid column transmission systems, and 4) micromanometric transducers.…”

Section: Discussionmentioning

confidence: 99%

Comparison of the frequency response characteristics of catheter‐mounted piezoelectric and micromanometric phonotransducers

Garcı́a

Layton

Rubal

1989

Cathet. Cardiovasc. Diagn.

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This study compares the frequency response characteristics of catheter-mounted piezoelectric sound transducers with micromanometric transducers. The tip of a 8F catheter with two piezoelectric transducers and two micromanometers was inserted into a water-filled chamber that had a speaker fixed at one end. The speaker was driven by a power amplifier and sine wave generator. The outputs of the transducers were connected to a low-level amplifier. The piezoelectric transducer behaved as a tunable high-pass filter that could be modified by altering the input impedance of the low level amplifier; the frequency response characteristics were examined at five input impedances ranging from 0.96 to 11.8 megohms. The peak-to-peak outputs of the piezoelectric and pressure transducers were recorded at frequency ranges from DC to 1 kHz with a wide-band oscilloscope. The ratio of the outputs from the piezotransducer and micromanometer (Vph/Vpr) was plotted vs. frequency for each input impedance and analyzed to determine the piezotransducer's output resistance and equivalent capacitance; roll-off frequencies were then calculated. The equivalent capacitance of the piezo-element was determined to be 500-700 picofarads. Series capacitance acted with network resistance to produce a predictable frequency-dependent change in signal amplitude and phase angle. The inherent noise of the pressure transducer was found to be approximately 0.2 mm Hg, while the noise of the piezoelectric transducer was immeasurably low. The piezoelectric phonotransducers were superior to micromanometer transducers in their higher gain and lower noise, suggesting that these transducers may prove useful to physiologic and clinical studies for measuring intravascular sound.

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