title: Evaluation of a novel Y-shaped extracardiac Fontan baffle using computational fluid dynamics.
abstract: OBJECTIVE
  The objective of this work is to evaluate the hemodynamic performance of a new Y-graft modification of the extracardiac conduit Fontan operation. The performance of the Y-graft design is compared to two designs used in current practice: a t-junction connection of the venae cavae and an offset between the inferior and superior venae cavae.
  
  
  METHODS
  The proposed design replaces the current tube grafts used to connect the inferior vena cava to the pulmonary arteries with a Y-shaped graft. Y-graft hemodynamics were evaluated at rest and during exercise with a patient-specific model from magnetic resonance imaging data together with computational fluid dynamics. Four clinically motivated performance measures were examined: Fontan pressures, energy efficiency, inferior vena cava flow distribution, and wall shear stress. Two variants of the Y-graft were evaluated: an "off-the-shelf" graft with 9-mm branches and an "area-preserving" graft with 12-mm branches.
  
  
  RESULTS
  Energy efficiency of the 12-mm Y-graft was higher than all other models at rest and during exercise, and the reduction in efficiency from rest to exercise was improved by 38%. Both Y-graft designs reduced superior vena cava pressures during exercise by as much as 5 mm Hg. The Y-graft more equally distributed the inferior vena cava flow to both lungs, whereas the offset design skewed 70% of the flow to the left lung. The 12-mm graft resulted in slightly larger regions of low wall shear stress than other models; however, minimum shear stress values were similar.
  
  
  CONCLUSIONS
  The area-preserving 12-mm Y-graft is a promising modification of the Fontan procedure that should be clinically evaluated. Further work is needed to correlate our performance metrics with clinical outcomes, including exercise intolerance, incidence of protein-losing enteropathy, and thrombus formation.
authors.affiliation: Mechanical and Aerospace Engineering Department, University of California, San Diego, Calif, USA.
authors.forename: Alison L
authors.initials: AL
authors.lastname: Marsden
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Bernstein
authors.forename: V Mohan
authors.initials: VM
authors.lastname: Reddy
authors.forename: Shawn C
authors.initials: SC
authors.lastname: Shadden
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Spilker
authors.forename: Frandics P
authors.initials: FP
authors.lastname: Chan
authors.forename: Charles A
authors.initials: CA
authors.lastname: Taylor
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Feinstein
mesh_terms: D001807:Blood Vessel Prosthesis; D017076:Computer-Aided Design; D018729:Fontan Procedure / Q000295:instrumentation / Q000379:methods*; D006439:Hemodynamics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D012039:Regional Blood Flow; D012212:Rheology; D014682:Vena Cava, Inferior / Q000503:physiopathology; D014683:Vena Cava, Superior / Q000503:physiopathology