title: In-vivo assessment of the morphology and hemodynamic functions of the BioValsalva™ composite valve-conduit graft using cardiac magnetic resonance imaging and computational modelling technology.
abstract: BACKGROUND
  The evaluation of any new cardiac valvular prosthesis should go beyond the classical morbidity and mortality rates and involve hemodynamic assessment. As a proof of concept, the objective of this study was to characterise for the first time the hemodynamics and the blood flow profiles at the aortic root in patients implanted with BioValsalva™ composite valve-conduit using comprehensive MRI and computer technologies.
  
  
  METHODS
  Four male patients implanted with BioValsalva™ and 2 age-matched normal controls (NC) underwent cardiac magnetic resonance imaging (MRI). Phase-contrast imaging with velocity-mapping in 3 orthogonal directions was performed at the level of the aortic root and descending thoracic aorta. Computational fluid dynamic (CFD) simulations were performed for all the subjects with patient-specific flow information derived from phase-contrast MR data.
  
  
  RESULTS
  The maximum and mean flow rates throughout the cardiac cycle at the aortic root level were very comparable between NC and BioValsalva™ patients (541 ± 199 vs. 567 ± 75 ml/s) and (95 ± 46 vs. 96 ± 10 ml/s), respectively. The maximum velocity (cm/s) was higher in patients (314 ± 49 vs. 223 ± 20; P = 0.06) due to relatively smaller effective orifice area (EOA), 2.99 ± 0.47 vs. 4.40 ± 0.24 cm2 (P = 0.06), however, the BioValsalva™ EOA was comparable to other reported prosthesis. The cross-sectional area and maximum diameter at the root were comparable between the two groups. BioValsalva™ conduit was stiffer than the native aortic wall, compliance (mm2 • mmHg(-1) • 10(-3)) values were (12.6 ± 4.2 vs 25.3 ± 0.4.; P = 0.06). The maximum time-averaged wall shear stress (Pa), at the ascending aorta was equivalent between the two groups, 17.17 ± 2.7 (NC) vs. 17.33 ± 4.7 (BioValsalva™ ). Flow streamlines at the root and ascending aorta were also similar between the two groups apart from a degree of helical flow that occurs at the outer curvature at the angle developed near the suture line.
  
  
  CONCLUSIONS
  BioValsalva™ composite valve-conduit prosthesis is potentially comparable to native aortic root in structural design and in many hemodynamic parameters, although it is stiffer. Surgeons should pay more attention to the surgical technique to maximise the reestablishment of normal smooth aortic curvature geometry to prevent unfavourable flow characteristics.
authors.forename: Emaddin
authors.initials: E
authors.lastname: Kidher
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Cheng
authors.forename: Omar A
authors.initials: OA
authors.lastname: Jarral
authors.forename: Declan P
authors.initials: DP
authors.lastname: O'Regan
authors.forename: Xiao Yun
authors.initials: XY
authors.lastname: Xu
authors.affiliation: The Department of Surgery and Cancer, Imperial College London, St Mary's Hospital, London W2 1NY, UK. t.athanasiou@imperial.ac.uk.
authors.forename: Thanos
authors.initials: T
authors.lastname: Athanasiou
mesh_terms: D000368:Aged; D019412:Anatomy, Cross-Sectional; D001011:Aorta / Q000502:physiology; D001013:Aorta, Thoracic / Q000502:physiology; D001021:Aortic Valve / Q000601:surgery*; D001783:Blood Flow Velocity / Q000502:physiology; D016022:Case-Control Studies; D003187:Compliance; D019295:Computational Biology / Q000379:methods*; D003198:Computer Simulation; D006350:Heart Valve Prosthesis; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D057446:Hydrodynamics; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009200:Myocardial Contraction / Q000502:physiology; D018583:Pliability; D011474:Prosthesis Design; D012039:Regional Blood Flow / Q000502:physiology; D013314:Stress, Mechanical