title: MRI shows limited mixing between systemic and pulmonary circulations in foetal transposition of the great arteries: a potential cause of in utero pulmonary vascular disease.
abstract: OBJECTIVE
  To investigate the relationship between foetal haemodynamics and postnatal clinical presentation in patients with transposition of the great arteries using phase-contrast cardiovascular magnetic resonance.
  
  
  BACKGROUND
  A severe and irreversible form of persistent pulmonary hypertension of the newborn occurs in up to 5% of patients with transposition and remains an important cause of morbidity and mortality in these infants. Restriction at the foramen ovale and ductus arteriosus has been identified as a risk factor for the development of pulmonary hypertension, and this can now be studied with magnetic resonance imaging using a new technique called metric optimised gating.
  
  
  METHODS
  Blood flow was measured in the major vessels of four foetuses with transposition with intact ventricular septum (gestational age range: 35-38 weeks) and compared with values from 12 normal foetuses (median gestational age: 37 weeks; range: 34-40 weeks).
  
  
  RESULTS
  We found significantly reduced flows in the ductus arteriosus (p<0.01) and foramen ovale (p=0.03) and increased combined ventricular output (p=0.01), ascending aortic (p=0.001), descending aortic (p=0.03), umbilical vein (p=0.03), and aorto-pulmonary collateral (p<0.001) flows in foetuses with transposition compared with normals. The foetus with the lowest foramen ovale shunt and highest aorto-pulmonary collateral flow developed fatal pulmonary vascular disease.
  
  
  CONCLUSIONS
  We found limited mixing between the systemic and pulmonary circulations in a small group of late-gestation foetuses with transposition. We propose that the resulting hypoxia of the pulmonary circulation could be the driver behind increased aorto-pulmonary collateral flow and contribute to the development of pulmonary vascular disease in some foetuses with transposition.
authors.affiliation: 1Department of Paediatrics,Hospital for Sick Children and University of Toronto,Toronto,Canada.
authors.forename: Prashob
authors.initials: P
authors.lastname: Porayette
authors.affiliation: 2Department of Physiology & Experimental Medicine,Hospital for Sick Children and University of Toronto,Toronto,Canada.
authors.forename: Joshua F P
authors.initials: JF
authors.lastname: van Amerom
authors.affiliation: 2Department of Physiology & Experimental Medicine,Hospital for Sick Children and University of Toronto,Toronto,Canada.
authors.forename: Shi-Joon
authors.initials: SJ
authors.lastname: Yoo
authors.affiliation: 1Department of Paediatrics,Hospital for Sick Children and University of Toronto,Toronto,Canada.
authors.forename: Edgar
authors.initials: E
authors.lastname: Jaeggi
authors.affiliation: 3Department of Diagnostic Imaging,Hospital for Sick Children and University of Toronto,Toronto,Canada.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Macgowan
authors.affiliation: 1Department of Paediatrics,Hospital for Sick Children and University of Toronto,Toronto,Canada.
authors.forename: Mike
authors.initials: M
authors.lastname: Seed
mesh_terms: D016022:Case-Control Studies; D005260:Female; D005865:Gestational Age; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications / Q000151:congenital; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D009864:Ontario; D011247:Pregnancy; D011651:Pulmonary Artery / Q000002:abnormalities / Q000503:physiopathology*; D011652:Pulmonary Circulation / Q000502:physiology*; D011668:Pulmonary Veno-Occlusive Disease / Q000150:complications / Q000151:congenital; D012039:Regional Blood Flow / Q000502:physiology; D014188:Transposition of Great Vessels / Q000150:complications* / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome
keywords: circulation