In the developing fetal heart in the first trimester, a complete failure of development of the spiral septum results in:
A Transposition of the great vessels
B Aortic arch interruption
C Persistent truncus arteriosus
D Atrioventricular septal defect
E Overriding aorta
(C) CORRECT. If the two spiral ridges of the truncus and conus fail to fuse and descend, then the aorta and pulmonic trunk are not separated, and there is usually a VSD as well.