title: An integrated macro/micro approach to evaluating pivot flow within the Medtronic ADVANTAGE bileaflet mechanical heart valve.
abstract: OBJECTIVE
  An integrated macro/micro approach was used to evaluate flow within the pivots of the Medtronic ADVANTAGE bileaflet heart valve. Results were compared with those obtained with the St. Jude Medical bileaflet heart valve.
  
  
  METHODS
  The integrated macro/micro approach consists of both a macroscopic hydrodynamic performance assessment and a three-part microscopic flow analysis. The hydrodynamic performance assesses the basic dynamic functions of the valves, while the microscopic flow analysis uses pivot flow visualization, computational fluid dynamics and laser Doppler velocimetry to determine pivot flow characteristics. Pivot flow visualization captures two-dimensional images of the pivot flow, defines the computational fluid dynamics boundary conditions, and validates the computational result. Three-dimensional unsteady computational fluid dynamics simulation reconstructs pivot flow structures. Laser Doppler velocimetry maps pivot velocity field and provides velocity validation for the computational simulation.
  
  
  RESULTS
  The macroscopic hydrodynamic performance assessment showed the ADVANTAGE and St. Jude Medical valves to be comparable under identical flow conditions. The three techniques in the microscopic analysis mutually confirmed that the pivot design of the ADVANTAGE valve permits continuous-flow washing in the pivot recess, the pivots of both valves are completely wiped twice in a cardiac cycle, and no persistent pivot flow stases are observed.
  
  
  CONCLUSIONS
  The integrated macro/micro approach represents a powerful systematic method for determining detailed microscopic flow structures inside the pivots of bileaflet mechanical valves. The use of this technique during the design process of a bileaflet valve can eliminate the persistent flow stases that lead to thrombus formation.
authors.affiliation: Medtronic Heart Valves, Inc., Santa Ana, CA 92705, USA.
authors.forename: Mark C S
authors.initials: MC
authors.lastname: Shu
authors.forename: Jeffery M
authors.initials: JM
authors.lastname: Gross
authors.forename: Keith K
authors.initials: KK
authors.lastname: O'Rourke
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D001021:Aortic Valve / Q000503:physiopathology* / Q000601:surgery*; D001698:Biomedical Engineering; D001783:Blood Flow Velocity / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D003198:Computer Simulation; D006350:Heart Valve Prosthesis; D006801:Humans; D021621:Imaging, Three-Dimensional; D017078:Laser-Doppler Flowmetry; D008943:Mitral Valve / Q000503:physiopathology* / Q000601:surgery*; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D012039:Regional Blood Flow / Q000502:physiology; D013314:Stress, Mechanical