title: Migration forces of transcatheter aortic valves in patients with noncalcific aortic insufficiency.
abstract: OBJECTIVE
  Transcatheter aortic valves have been successfully implanted into the calcified leaflets of patients with severe aortic stenosis. However, their stability in patients with noncalcified aortic insufficiency is unknown. Similar to thoracic and abdominal aortic stent grafts, transcatheter aortic valves are subjected to antegrade ejection forces during systole. However, retrograde migration forces into the left ventricle are also generated by the diastolic pressure gradient across the closed valve. It has been suggested that leaflet calcification anchors the prosthesis, and measurements of migration forces should be considered before clinical trials in noncalcified aortic insufficiency. The objective of this study was to use computational fluid dynamics simulations to quantify forces that could potentially dislodge the prosthesis.
  
  
  METHODS
  A computational fluid dynamics model was developed to simulate systolic flow through a geometric mesh of the aortic root and transcatheter aortic valves. Hemodynamic measurements were made at discrete moments during ejection. Unsteady control volume analysis was used for calculations of force on the mesh.
  
  
  RESULTS
  Results of the simulation indicate that a total force of 0.602 N acts on the transcatheter aortic valves during systole, 99% of which is in the direction of axial flow. The largest contributor to force was the dynamic pressure gradient through the transcatheter aortic valves. This antegrade force is approximately 10 times smaller than the retrograde force (6.01 N) on the closed valve during diastole.
  
  
  CONCLUSIONS
  Our model simulated systolic flow through a transcatheter aortic valve and demonstrated migration into the left ventricle to be of greater concern than antegrade ejection.
authors.affiliation: Department of Mechanical and Aeronautic Engineering, University of California at Davis, Davis, CA, USA.
authors.forename: Harry A
authors.initials: HA
authors.lastname: Dwyer
authors.forename: Peter B
authors.initials: PB
authors.lastname: Matthews
authors.forename: Ali
authors.initials: A
authors.lastname: Azadani
authors.forename: Liang
authors.initials: L
authors.lastname: Ge
authors.forename: T Sloane
authors.initials: TS
authors.lastname: Guy
authors.forename: Elaine E
authors.initials: EE
authors.lastname: Tseng
mesh_terms: D001021:Aortic Valve / Q000503:physiopathology* / Q000601:surgery*; D001022:Aortic Valve Insufficiency / Q000503:physiopathology* / Q000601:surgery*; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D003198:Computer Simulation; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000295:instrumentation; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D013314:Stress, Mechanical; D013599:Systole