title: An in vitro assessment by means of laser Doppler velocimetry of the medtronic advantage bileaflet mechanical heart valve hinge flow.
abstract: OBJECTIVE
  The aim of this study was to evaluate the hinge flow field characteristics of the Medtronic Advantage bileaflet valve and compare them with the flow fields of the St Jude Medical standard valve. The present study provides laser Doppler velocimetry results for the Advantage and St Jude Medical valves to make a direct comparison of the flow fields of the 2 valve designs. This study aids in determining the preclinical efficacy of Medtronic's new bileaflet valve hinge design.
  
  
  METHODS
  Two-dimensional laser Doppler velocimetry was used to measure the velocities in the hinge regions of size 29 Medtronic Advantage and St Jude Medical standard bileaflet valve designs. Exact dimensional models of the bileaflet valves, including the hinge regions, were cast from transparent plastic materials to conduct these measurements under simulated physiologic conditions. Laser Doppler velocimetry measurements were conducted under physiologic conditions, with the valves placed in the mitral position of a pulsatile flow loop. Measurements were taken at several elevation levels in the hinge region. Multiple measurement locations obtained in each plane provided a grid work by which the flow fields could be detailed.
  
  
  RESULTS
  Velocity measurements obtained for each valve design in the hinge recess were used to reconstruct the flow fields. For the Advantage valve, the peak velocities during leakage flow in the hinge at zero depth, one-third depth, and two-thirds depth levels into the hinge recess were 0.9, 1.6, and 1.8 m/s, respectively. Corresponding values for the St Jude Medical valve were 1.3, 1.6, and 2.1 m/s, respectively. From the reconstructed flow fields, the flow patterns seen within the 2 hinge designs exhibited similar features, with more dynamic flow patterns observed in the Advantage hinge during the forward flow phase.
  
  
  CONCLUSIONS
  The present study demonstrated that the hinge flow dynamics of the Advantage bileaflet design were similar to those of the St Jude Medical hinge design. The velocities within the hinge were slightly higher for the St Jude Medical valve but not significantly different. There appears to be more dynamic flow through the hinge of the Advantage valve during the forward flow phase.
authors.affiliation: Wallace H. Coulter School of Biomedical Engineering, Cardiovascular Fluid Mechanics Laboratory, Georgia Institute of Technology, Atlanta 30332-0535, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Saxena
authors.forename: Jack
authors.initials: J
authors.lastname: Lemmon
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Ellis
authors.forename: Ajit
authors.initials: A
authors.lastname: Yoganathan
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D003971:Diastole / Q000502:physiology; D006350:Heart Valve Prosthesis; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008943:Mitral Valve / Q000503:physiopathology* / Q000601:surgery*; D008955:Models, Cardiovascular; D011474:Prosthesis Design / Q000295:instrumentation; D011673:Pulsatile Flow / Q000502:physiology; D013599:Systole / Q000502:physiology