title: Reduction of aberrant aortic haemodynamics following aortic root replacement with a mechanical valved conduit.
abstract: Previous work suggests that aortic root and valve prostheses alter blood flow patterns in the ascending aorta, creating aberrant haemodynamics compared with those of healthy volunteers. Various valve designs have been proposed to better restore physiological haemodynamics. In this study, magnetic resonance imaging (MRI) was used to non-invasively assess three-dimensional (3D) ascending aortic haemodynamics after aortic root replacement (ARR) with a mechanical valved conduit postulated to create less turbulent blood flow.
  
  
  
  Ten patients (40 ± 9 years) underwent transthoracic echocardiography and contrast-enhanced multidimensional four-dimensional (4D) flow MRI at 1.5 T after ARR with an On-X mechanical valved conduit. Preoperative 4D flow MRI was available in 7 patients. Ten age- and gender-matched healthy volunteers (42 ± 13 years) were also analysed to characterize physiological flow. The presence of vortex/helix formation was graded by two blinded observers. Peak transvalvular pressure gradients were computed using the simplified Bernoulli equation. Patients' postoperative pressure gradients and helicity/vorticity grades were compared with preoperative gradients and those from healthy volunteers.
  
  
  
  Intra- and interobserver ratings showed good agreement (κ = 0.93, P < 0.01 and κ = 0.84, P < 0.01, respectively). Highly helical and/or vortical flow was observed in all patients preoperatively, which was significantly reduced postoperatively (P < 0.01 and <0.01, respectively), restoring similar flow patterns similar to those seen in volunteers (P = 0.56 and 0.56). Peak transvalvular pressure gradients (ΔP) were also significantly reduced [43 ± 21 vs 12 ± 7 mmHg, P < 0.05 (Echo); 48 ± 22 vs 16 ± 9 mmHg, P < 0.05 (MRI)], but remained significantly higher than those of volunteers (6 ± 1 mmHg, P < 0.01).
  
  
  
  Preliminary evidence suggests that ARR with an On-X mechanical valve significantly reduces aberrant aortic haemodynamics, producing flow patterns that resemble those in healthy volunteers.
authors.affiliation: Department of Radiology, Northwestern University, Chicago, IL, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Keller
authors.affiliation: Division of Surgery-Cardiac Surgery, Northwestern University, Chicago, IL, USA.
authors.forename: S Chris
authors.initials: SC
authors.lastname: Malaisrie
authors.affiliation: Division of Surgery-Cardiac Surgery, Northwestern University, Chicago, IL, USA.
authors.forename: Jane
authors.initials: J
authors.lastname: Kruse
authors.affiliation: Division of Surgery-Cardiac Surgery, Northwestern University, Chicago, IL, USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: McCarthy
authors.affiliation: Department of Radiology, Northwestern University, Chicago, IL, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Carr
authors.affiliation: Department of Radiology, Northwestern University, Chicago, IL, USA Department of Biomedical Engineeringy, Northwestern University, Evanston, IL, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.affiliation: Department of Radiology, Northwestern University, Chicago, IL, USA Department of Biomedical Engineeringy, Northwestern University, Evanston, IL, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Barker
authors.affiliation: Department of Radiology, Northwestern University, Chicago, IL, USA collins@fsm.northwestern.edu.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Collins
mesh_terms: D000328:Adult; D001011:Aorta / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging / Q000601:surgery*; D001021:Aortic Valve / Q000000981:diagnostic imaging / Q000601:surgery*; D019561:Echocardiography, Four-Dimensional; D005260:Female; D064368:Healthy Volunteers; D006350:Heart Valve Prosthesis; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D012372:ROC Curve
keywords: Aortic valve replacement; Magnetic resonance imaging; Mechanical heart valve prosthesis