title: Noise levels of closing sounds in vivo are equal for different bileaflet mechanical heart valves.
abstract: OBJECTIVE
  Patients with mechanical heart valves must endure the valve's closing sounds for the rest of their life. Sound pressure levels (SPLs) recorded show wide patient-to-patient variation, even for the same type of valve. The variation was attributed to body constitution variability and differences in hemodynamic status. It was hypothesized that aortic mechanical valves generate closing clicks which correlate in magnitude with hemodynamic parameters, such as the rate of relaxation of the left ventricle (dp/dt) and potential energy stored in the aortic windkessel.
  
  
  METHODS
  Three different aortic mechanical heart valves were investigated in a porcine model (n = 9), namely St. Jude Medical, CarboMedics and ATS. Closing sounds were measured with a microphone placed in a portable anechoic chamber 10 cm above the exposed heart. Left ventricular pressure (LVP) and cardiac output were also measured. Different hemodynamic conditions were produced by intravenous infusion of isotonic saline and dobutamine. Volume regulation and atrial pacing were also applied.
  
  
  RESULTS
  Different hemodynamic situations were established (cardiac output, 1.2-6.5 l/min; heart rate, 99-171 bpm). The measured mean SPLs were 49.5-53.9 dB(A), and there were no statistically significant differences in noise between the valves (p = 0.8; one-way ANOVA). Likewise, only a weak relationship was identified between different hemodynamic parameters and the SPLs recorded.
  
  
  CONCLUSIONS
  The SPLs of the investigated bileaflet mechanical heart valves did not differ significantly. Moreover, the SPL was only weakly related to LVP during closure and estimated stroke work.
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Experimental Clinical Research, Aarhus University Hospital Skejby Sygehus, Aarhus, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Johansen
authors.forename: Søren Berndt
authors.initials: SB
authors.lastname: Hansen
authors.forename: J Michael
authors.initials: JM
authors.lastname: Hasenkam
authors.forename: Hans
authors.initials: H
authors.lastname: Nygaard
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001021:Aortic Valve / Q000601:surgery; D001705:Bioprosthesis; D006347:Heart Sounds; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation; D008144:Loudness Perception; D023421:Models, Animal; D012680:Sensitivity and Specificity; D013018:Sound Spectrography; D013552:Swine; D016277:Ventricular Function, Left / Q000502:physiology