The Journal of Thoracic and Cardiovascular Surgery, Vol 101, 1060-1068, Copyright © 1991 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Acoustic analysis of the closing sounds of bileaflet prosthetic valves in a sheep model
RL Donnerstein, WA Scott, A Vasu and JG Copeland
Department of Pediatrics, University of Arizona, Health Sciences Center, Tucson 85724.
Previous investigations of mechanical valve sounds have shown that (1)
frequency spectra of sounds produced by abnormal valves differ from those
of properly functioning valves and (2) leaflets of normally functioning
bileaflet valves do not close synchronously. This investigation studied
effects of mechanical valve size, environment, and hemodynamic state on
closing sounds. A single 25 mm bileaflet mitral mechanical valve was
implanted in six sheep and a single 27 mm valve in four sheep. With digital
signal processing, asynchronous leaflet closure and frequency spectra were
assessed after alterations in animal position, respiratory phase, heart
rate, afterload, contractility, and preload. Both asynchronous leaflet
closure and frequency spectra varied among animals, and, except for a
decrease in asynchrony with increasing contractility, were largely
independent of valve size and hemodynamics. Baseline asynchrony ranged from
0.5 to 4.2 msec. Frequency spectra were characterized by the first three
resonant peaks. Lowest resonant peaks ranged from 2.5 to 3.4 kHz, middle
from 4.7 to 6.8 kHz, and highest from 7.2 to 9.6 kHz. These results
indicate that accurate assessment of mechanical valve function with
acoustic analysis requires baseline studies in all patients by means of a
system with a frequency response of more than 10 kHz.
