The Complexity of External Acoustic Detection of Defects in Björk‐Shiley Convexoconcave Heart Valves

Abstract

It is the goal of this section to publish material that provides information regarding specific issues, aspects of artificial organ application, approach, philosophy, suggestions, and/or thoughts for the future.Abstract: The prevalence of antihepatitis virus C (HCV) antibodies in chronic hemodialysis (HD) patients is higher than in normal populations, and yet hepatocellular carcinoma (HCC) is infrequent in chronic HD patients who are HCV antibody positive. In this study, we investigated the characteristics of HCV-antibody-positive patients with HCC on chronic HD. A total of 6,366 cases of HCVantibody-positive patients on chronic HD therapy was analyzed on the basis of answers to questionnaires on the incidence rate of HCC in 314 Japanese dialysis institutions. HCC was a complication in 114 of 6,222 (1.8%) HCVantibody-positive patients, and cirrhosis was a complication in 536 of 6,242 (8.6%). The incidence rate of both complications was significantly higher in males than in females, and the incidence rate in the chronic HD patients was much lower than in normal populations. Specific immunological status in patients on chronic HD therapy may be an important key for preventing the progression of chronic HCV hepatitis. However, further research is needed because this study was preliminary and excluded the type of HCV virus, pathological findings, and laboratory data.

Development and validation of implantable sensors for monitoring function of prosthetic heart valves:in vitro studies

“…This variation in frequency range is presumably due to two differences between the studies: first, a mono-leaflet valve was used in their study; secondly, the thrombus was attached in a manner that would primarily affect the resonance frequencies of the valve structures, whereas we attached the thrombus so that it would interfere with leaflet closing. PLEMONDS and HOVENGA (1995) and DE MOL et al (2001) have shown resonance frequencies to be located at the higher end of the frequency spectrum of the closing sound.…”

“…REYNOLDS and STEPHEN (1995) went so far as to submerge patients during valve sound recording to minimise the effects of the air-chest interface. Modelling acoustic sound propagation within the thorax, DE MOL et al (2001) found that valve sound amplitude was severely position dependent and that phase reversals were possible as well. Although the model showed that submerging the patient in water did help with reflections at the chest interface, obtaining consistent, high-quality external recordings was still difficult.…”

“…Both phenomena are highly interrelated, resulting in a mixed propagation of a vibro-acoustic signal. In addition, different tissues have varying propagation velocities, reflection coefficients and attenuation; the result is a complex and distorted signal at the chest-air interface (DE MOL et al, 2001).…”

Detecting broken struts of a BjÖrk-Shiley heart valve using ultrasound: A feasibility study

“…The time period between the first and second fracture is highly variable (Walker and Scotten 1991;Plemons et al 1994;de Mol et al 1997de Mol et al , 2001. However, in vitro investigations by Health and Welfare Canada, the US Food and Drug Administration (FDA) and Shiley Inc. have demonstrated that valves with a single-strut fracture have operated in vitro under simulated normal conditions for extended periods of time without critical failure (Walker and Scotten 1991).…”

“…1) The chest is a highly complex medium, in which attenuation, reflection and diffraction caused by the different structures in the chest have an effect on the shape of the acoustic wave field (Sava et al 1995;de Mol et al 2001 2) The BScc valve has not been designed for the acoustic assessment of wear and fractures in the outlet strut legs and does not behave as a monopole source (de Mol et al 2001). …”