title: Blood flow characteristics in the ascending aorta after aortic valve replacement--a pilot study using 4D-flow MRI.
abstract: BACKGROUND
  Aortic remodeling after aortic valve replacement (AVR) might be influenced by the postoperative blood flow pattern in the ascending aorta. This pilot study used flow-sensitive four-dimensional magnetic resonance imaging (4D-flow) to describe ascending aortic flow characteristics after various types of AVR.
  
  
  METHODS
  4D-flow was acquired in 38 AVR patients (n=9 mechanical, n=8 stentless bioprosthesis, n=14 stented bioprosthesis, n=7 autograft) and 9 healthy controls. Analysis included grading of vortex and helix flow (0-3 point scale), assessment of systolic flow eccentricity (1-3 point scale), and quantification of the segmental distribution of peak systolic wall shear stress (WSS(peak)) in the ascending aorta.
  
  
  RESULTS
  Compared to controls, mechanical prostheses showed the most distinct vorticity (2.7±0.5 vs. 0.7±0.7; p<0.001), while stented bioprostheses exhibited most distinct helicity (2.6±0.7 vs. 1.6±0.5; p=0.002). Instead of a physiologic central flow, all stented, stentless and mechanical prostheses showed eccentric flow jets mainly directed towards the right-anterior aortic wall. Stented and stentless prostheses showed an asymmetric distribution of WSS(peak) along the aortic circumference, with significantly increased local WSS(peak) where the flow jet impinged on the aortic wall. Local WSS(peak) was higher in stented (1.4±0.7 N/m(2)) and stentless (1.3±0.7 N/m(2)) compared to autografts (0.6±0.2 N/m(2); p=0.005 and p=0.008) and controls (0.7±0.1 N/m(2); p=0.017 and p=0.027). Autografts exhibited lower absolute WSS(peak) than controls (0.4±0.1 N/m(2) vs. 0.7±0.2 N/m(2); p=0.003).
  
  
  CONCLUSIONS
  Flow characteristics in the ascending aorta after AVR are different from native aortic valves and differ between various types of AVR.
authors: Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine; and HELIOS Klinikum Berlin Buch, Department of Cardiology and Nephrology, Berlin, Germany. Electronic address: florian.von-knobelsdorff@charite.de.
authors: Florian
authors: F
authors: von Knobelsdorff-Brenkenhoff
authors: Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine; and HELIOS Klinikum Berlin Buch, Department of Cardiology and Nephrology, Berlin, Germany.
authors: Ralf F
authors: RF
authors: Trauzeddel
authors: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors: Alex J
authors: AJ
authors: Barker
authors: Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine; and HELIOS Klinikum Berlin Buch, Department of Cardiology and Nephrology, Berlin, Germany.
authors: Henriette
authors: H
authors: Gruettner
authors: Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, IL, USA.
authors: Michael
authors: M
authors: Markl
authors: Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine; and HELIOS Klinikum Berlin Buch, Department of Cardiology and Nephrology, Berlin, Germany.
authors: Jeanette
authors: J
authors: Schulz-Menger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001011:Aorta / Q000502:physiology*; D001021:Aortic Valve / Q000502:physiology* / Q000503:physiopathology / Q000601:surgery; D000082882:Bicuspid Aortic Valve Disease; D001705:Bioprosthesis; D001783:Blood Flow Velocity / Q000502:physiology; D057791:Cardiac Imaging Techniques / Q000379:methods; D005260:Female; D006330:Heart Defects, Congenital / Q000503:physiopathology / Q000601:surgery*; D006349:Heart Valve Diseases / Q000503:physiopathology / Q000601:surgery*; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D015607:Stents
keywords: 4D-flow; Aorta; Hemodynamics; Magnetic resonance imaging; Surgery; Valves