title: The outflow tract in transposition of the great arteries: an anatomic and morphologic study.
abstract: BACKGROUND
  Neoaortic root dilatation is observed after the arterial switch operation for transposition of the great arteries. Although structural differences in the vessel wall of these patients may be of influence, we hypothesize that a histomorphologic difference in composition and embedding of the fibrous annulus in transposition of the great arteries may play a role in neoaortic root dilatation.
  
  
  METHODS
  Two normal human hearts and two unoperated human hearts with transposition of the great arteries, 1 day postnatal, were studied. Histologic sections stained for collagen, myocardium, and elastin were prepared, and three-dimensional reconstructions of the outflow tracts were made to enable comparison of the morphologic structures between the normal hearts and those with transposition of the great arteries.
  
  
  RESULTS
  The amount of collagen in the arterial roots was diminished in hearts with transposition of the great arteries compared with the normal hearts. In addition, the anchorage and embedding of both arterial roots in the myocardium was less extensive in transposition of the great arteries. The changed position of the arteries in the malformed hearts results in less support for the roots from the surrounding atrioventricular myocardium.
  
  
  CONCLUSIONS
  The combination of the observed histomorphologic differences in amount of collagen and myocardial support may be an explanation for the neoaortic root dilatation observed after the arterial switch operation. The developmental background of the observed deficient fibrous annulus formation may originate from an epicardial problem.
authors.affiliation: Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Shirin
authors.initials: S
authors.lastname: Lalezari
authors.forename: Edris A F
authors.initials: EA
authors.lastname: Mahtab
authors.forename: Margot M
authors.initials: MM
authors.lastname: Bartelings
authors.forename: Lambertus J
authors.initials: LJ
authors.lastname: Wisse
authors.forename: Mark G
authors.initials: MG
authors.lastname: Hazekamp
authors.forename: Adriana C
authors.initials: AC
authors.lastname: Gittenberger-de Groot
mesh_terms: D002102:Cadaver; D003094:Collagen / Q000032:analysis*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007231:Infant, Newborn; D009206:Myocardium / Q000737:chemistry / Q000473:pathology*; D014188:Transposition of Great Vessels / Q000378:metabolism / Q000473:pathology*
chemical_list: D003094:Collagen