Shortened outflow tract leads to altered cardiac looping after neural crest ablation.
BACKGROUND
Congenital conotruncal malformations frequently involve dextroposed aorta. The pathogenesis of dextroposed aorta is not known but is thought to be due to abnormal looping and/or wedging of the outflow tract during early heart development. We examined the stage of cardiac looping in an experimental model of dextroposed aorta to determine the embryogenesis of this conotruncal malformation.


RESULTS
Hearts were examined from neural crest-ablated embryos by using videocinephotography, scanning electron microscopy, and histological sections. The inflow and outflow limbs of the looped cardiac tube were malpositioned with respect to each other, the inner curvature was diminished, and the outflow limb was straighter and displaced cranially in a manner consistent with diminished length. The altered length could be explained by a significant reduction in the number of cells added to the myocardium of the distal outflow tract from the secondary heart field.


CONCLUSIONS
The data are consistent with research showing that normal looping and wedging are essential for normal alignment of the aorta with the left ventricle. These processes are abnormal in neural crest-ablated embryos because of a failure of the outflow tract to lengthen by the addition of myocardial cells from the secondary heart field.
Neonatal Perinatal Research Institute, Division of Neonatology, Duke University Medical Center, Durham, NC 27710, USA.
T Mesud
TM
Yelbuz
Karen L
KL
Waldo
Donna H
DH
Kumiski
Harriett A
HA
Stadt
Raymond R
RR
Wolfe
Linda
L
Leatherbury
Margaret L
ML
Kirby
D000818:Animals; D001011:Aorta / Q000002:abnormalities* / Q000196:embryology; D002642:Chick Embryo; D006321:Heart / Q000196:embryology; D006330:Heart Defects, Congenital / Q000209:etiology* / Q000473:pathology; D007700:Kinetics; D018715:Microscopy, Video; D009206:Myocardium / Q000473:pathology / Q000648:ultrastructure; D009432:Neural Crest / Q000601:surgery