title: Blood flow measured by magnetic resonance imaging at rest and exercise after surgical bypass of aortic arch obstruction.
abstract: BACKGROUND
  Blood flow distribution after ascending-to-descending aortic bypass in complex aortic arch obstruction is poorly described.
  
  
  OBJECTIVE
  To study blood flow by magnetic resonance (MR) imaging at rest and during exercise in patients with aortic arch obstruction and a bypass tube and in healthy controls.
  
  
  METHODS
  Seven patients (median 18 years (range: 14-54 years) and weight 79 kg (range 51-91 kg)) were studied 25 months (range 6-68 months) following surgical insertion of 14- or 16-mm bypass tube from the ascending to the distal descending thoracic aorta. Seven sex- and aged-matched normotensive subjects served as controls. MR real-time flow was measured in the ascending aorta and the proximal descending thoracic aorta in all participants and in the bypass tube in patients at rest and during supine leg exercise at 0.5 and 1.0 W kg(-1).
  
  
  RESULTS
  Ascending aortic flow at rest in patients was 2.9l min(-1)m(-2) (range 2.3-4.4) and increased with exercise to 5.3 (range 4.3-7.3) at 1.0 W kg(-1), which was not different from controls (3.4 (range 2.4-4.6) and 6.1 (range 5.0-6.9)). The bypass tube carried roughly the same flow as the proximal descending aorta at rest (1.5 (range 0.7-2.0) and 1.0 (range 0.2-2.0), respectively, and flows increased similarly during exercise (2.8 (range 1.5-4.0) and 2.0 (range 0.8-4.1), respectively at 1.0 W kg(-1)). Flow to the upper body did not differ between groups nor changed with supine leg exercise.
  
  
  CONCLUSIONS
  With aortic arch obstruction, an ascending-to-descending aortic bypass tube provides normal flow to the lower body at rest and during supine leg exercise without evidence of steal from the upper body.
authors.affiliation: Department of Cardiothoracic Surgery, Institute of Clinical Medicine, Skejby Hospital, Aarhus University Hospital, Brendstrupgårdsvej 100, DK 8200 Aarhus, Denmark.
authors.forename: Lia Mendes
authors.initials: LM
authors.lastname: Pedersen
authors.forename: Thais Almeida Lins
authors.initials: TA
authors.lastname: Pedersen
authors.forename: Erik Morre
authors.initials: EM
authors.lastname: Pedersen
authors.forename: Hilde
authors.initials: H
authors.lastname: Højmyr
authors.forename: Kristian
authors.initials: K
authors.lastname: Emmertsen
authors.forename: Vibeke Elisabeth
authors.initials: VE
authors.lastname: Hjortdal
mesh_terms: D000293:Adolescent; D000328:Adult; D001011:Aorta / Q000503:physiopathology; D001013:Aorta, Thoracic / Q000002:abnormalities / Q000503:physiopathology / Q000601:surgery*; D001017:Aortic Coarctation / Q000601:surgery*; D019917:Blood Vessel Prosthesis Implantation / Q000379:methods*; D016022:Case-Control Studies; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D012039:Regional Blood Flow / Q000502:physiology; D012146:Rest / Q000502:physiology; D055815:Young Adult