Arrested rotation of the outflow tract may explain double-outlet right ventricle.

In a previous study the possibility that tetralogy of Fallot and transposition of the great arteries may result of embryonic arrests in the normal rotation of the junction of the outflow tract and the great arteries was investigated. The results suggested that the development of other transposition complexes such as double-outlet right ventricle might also be related to arrests in this process of rotation. To further study this question 20 normal hearts and 15 hearts with double-outlet right ventricle obtained at autopsy were studied. 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 mean angle was 81 +/- 7(SE) degrees. For 13 of the 15 hearts with double-outlet right ventricle the mean angle was 4 +/- 7(SE) degrees. Two hearts with double-outlet right ventricle showed markedly divergent aortic-to-pulmonary valve angles, with a mean of 228 +/- 11(SE) degrees, and were therefore grouped separately. Although direct comparison of hearts and embryos is difficult because of the differences in methods of determining angles, the valve positions in normal hearts was most similar to Carnegie stage 19, as found in an earlier study. The majority of the hearts with double-outlet right ventricle resembled stage 16 embryos. The results of this study, as well as those of the earlier studies, support the hypothesis that a spectrum of cardiac anomalies with anomalous origin of great vessels arises as arrests in the normal rotation of the semilunar valve region during embryogenesis.