Subject(s)
Gait , Leg , Meningitis, Meningococcal/physiopathology , Pain/etiology , Child, Preschool , Diagnosis, Differential , Female , Humans , Male , Meningitis, Meningococcal/diagnosisABSTRACT
In a previous study we investigated the rapidly changing spatial relationship of the junction of the outflow tract and great arteries in normal human embryos of Carnegie stages 15 through 19. The results suggested that the malformation complexes tetralogy of Fallot and transposition of the great arteries could be accounted for as arrests in the progression of this process of rotation. To further study this question we reviewed hearts obtained at autopsy: 28 were normal, 16 had tetralogy of Fallot, and 27 had transposition of the great arteries. The angle of the aortic to pulmonary valve axis relative to the inferior surface of the heart, as viewed from apex to base, was measured from postmortem radiographs. For normal hearts the angle was 72 degrees +/- 3 SE, 48 degrees +/- 5 for tetralogy of Fallot, and 333 degrees +/- 3 for transposition of the great arteries. Although direct comparison of hearts and embryos is difficult because of the different methods of determining angles, the valve positions in normal hearts were most similar to stage 19 embryos. Likewise, hearts with tetralogy of Fallot and transposition of the great arteries resembled stages 18 and 15, respectively. The results of the two studies are consistent with the hypothesis that tetralogy of Fallot and transposition of the great arteries arise as a result of arrests in the normal rotation of the region of the junction of the outflow tract and the great arteries.
Subject(s)
Heart/embryology , Tetralogy of Fallot/etiology , Transposition of Great Vessels/etiology , Humans , Tetralogy of Fallot/pathology , Transposition of Great Vessels/pathologyABSTRACT
The factors which give rise to the normal relationship between the great arteries and their respective ventricles are unknown. The developmental anatomy of this region was studied by using frontal, sagittal, or transverse serial histologic sections of 17 normal human embryos of Carnegie stages 15-19 from the Carnegie Embryological Collection. Distances and angles between major anatomic landmarks were determined by using computer reconstructions of the serially sectioned embryos, three-dimensional analytic geometry, and Euclidean distance formulas. The findings show that between stages 15 and 19 there is a marked rotation of the axis of the semilunar valves: frontal 121 degrees counterclockwise, sagittal 196 degrees counterclockwise, and transverse 240 degrees clockwise. Simultaneously the great arteries lengthen at a faster rate than the rest of the heart; and there is also an increase in the caliber and wall thickness of the great arteries. These results suggest that the changing rate of growth between the great arteries and the heart is necessary to align the great arteries, the semilunar valves, and the muscular outflow tract septum appropriately with respect to the interventricular septum. Reductions in the rate of growth of the great arteries relative to the heart could, by causing changes in the rotation of great arteries and outflow tract septum, have a role in the pathogenesis of cardiovascular malformations such as tetralogy of Fallot and transposition of the great arteries.
