title: Treatment of aortic stenosis with aortic valve bypass (apicoaortic conduit) surgery: an assessment using computational modeling.
abstract: BACKGROUND
  Aortic valve bypass surgery treats aortic valve stenosis with a valve-containing conduit that connects the left ventricular apex to the descending thoracic aorta. After aortic valve bypass, blood is ejected from the left ventricle via both the native stenotic aortic valve and the conduit. We performed computational modeling to determine the effects of aortic valve bypass on aortic and cerebral blood flow, as well as the effect of conduit size on relative blood flow through the conduit and the native valve.
  
  
  METHODS
  The interaction of blood flow with the vascular boundary was modeled using a hybrid Eurelian-Lagrangian formulation, where an unstructured Galerkin finite element method was coupled with an immersed boundary approach.
  
  
  RESULTS
  Our model predicted native (stenotic) valve to conduit flow ratios of 45:55, 52:48, and 60:40 for conduits with diameters of 20, 16, and 10 mm, respectively. Mean gradients across the native aortic valve were calculated to be 12.5, 13.8, and 17.6 mm Hg, respectively. Post-aortic valve bypass cerebral blood flow was unchanged from preoperative aortic valve stenosis configurations and was constant across all conduit sizes. In all cases modeled, cerebral blood flow was completely supplied by blood ejected across the native aortic valve.
  
  
  CONCLUSIONS
  An aortic valve bypass conduit as small as 10 mm results in excellent relief of left ventricular outflow tract obstruction in critical aortic valve stenosis. The presence of an aortic valve bypass conduit has no effect on cerebral blood flow. All blood flow to the brain occurs via antegrade flow across the native stenotic valve; this configuration may decrease the long-term risk of cerebral thromboembolism.
authors.affiliation: Department of Mechanical Engineering, University of Maryland Medical Center, Baltimore, MD 21201, USA.
authors.forename: Elias
authors.initials: E
authors.lastname: Balaras
authors.forename: K S
authors.initials: KS
authors.lastname: Cha
authors.forename: Bartley P
authors.initials: BP
authors.lastname: Griffith
authors.forename: James S
authors.initials: JS
authors.lastname: Gammie
mesh_terms: D001013:Aorta, Thoracic / Q000601:surgery*; D001021:Aortic Valve / Q000601:surgery*; D001024:Aortic Valve Stenosis / Q000601:surgery*; D006348:Cardiac Surgical Procedures / Q000379:methods; D003198:Computer Simulation; D006352:Heart Ventricles / Q000601:surgery*; D014656:Vascular Surgical Procedures / Q000379:methods