Rotation of the junction of the outflow tract and great arteries in the embryonic human heart

Abstract

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.

Cardiac outflow tract: A review of some embryogenetic aspects of the conotruncal region of the heart

“…Indeed, previous studies on human embryos (Goor et al, 1972;Lomonico et al, 1986) and chick embryos (Dor and Corone, 1985;Thompson et al, 1987) suggested that the conotruncus undergoes this sort of rotation during its remodeling.…”

Rotation of the Myocardial Wall of the Outflow Tract Is Implicated in the Normal Positioning of the Great Arteries

“…24 Computerization of distances and angles between major anatomical landmarks, in particular the axis of the semilunar valves, showed that the junction of the OFT and the great arteries undergoes a rapid rotation in a counterclockwise direction, facing downstream, between Carnegie stages 15 and 19. 24 In addition, the angle of the aortic to pulmonary valve axis, relative to the inferior surface of congenitally malformed hearts, suggested that TOF, DORV, and TGA may result from an arrested rotation of the outflow region at the base of the great arteries. 25,26 We now report a counterclockwise rotation of OFT myocardium in the mouse embryo and examine this phenomenon in mice with OFT defects.…”

Myocardial progenitors in the pharyngeal regions migrate to distinct conotruncal regions

“…These observations suggest that during OFT development (1) cells from the SHF migrate rotationally in a counterclockwise direction towards the OFT (viewed from the apex), (2) myocardial progenitor cells from the AHF migrate to the ventral wall of the OFT in a non-rotational manner, and (3) heart progenitors in the SHF and AHF contribute to the formation of distinct conotruncal regions. A previous developmental anatomy study involving human embryos showed that the junction of the OFT and the great arteries undergoes rapid rotation between Carnegie stages 15 and 19 (Lomonico et al, 1986). Ward et al (2005) showed that the dye-labeled right side of the SHF migrates spirally to the left side of the OFT in chicks.…”