Right-sided aortic arch and tetralogy of Fallot in humans--a morphological study of 10 cases.

Introduction: A right-sided aortic arch (RAA) represents a rare anomaly of the cardiovascular system. In situs solitus, RAA is typically associated with malformations of the cardiac outflow tract such as tetralogy of Fallot (TOF). RAA is classified according to the course and ramification pattern and the position of the arterial duct. Varying data on the frequency of the RAA ramification patterns are reported in the literature.

Methods: We examined 10 formalin-fixed human specimens aged 3 weeks to 10 years. In each case, we investigated the course of the aortic arch, its ramification and the position and course of the arterial duct/ligament as well as associated cardiac malformations.

Results: Three different ramification patterns became evident: mirror-image branching (n=7), aberrant left subclavian artery (n=2) and isolated left subclavian artery (n=1). The arterial duct was situated either on the left side connecting the left pulmonary artery to the left subclavian artery (n=6) or on the right-hand side between the right pulmonary artery and the aortic arch (n=3). The duct was absent in one case. The most frequent combination was a mirror-image branching pattern with a left-sided arterial duct (n=4).

Conclusions: The various ramification patterns of the RAA are explained by differences in growth and involution of the embryonic double-aortic arch "anlage." Genetic factors as well as mechanical influences may be involved in the aetiology of RAA. The percentage of the various RAA patterns strongly depends on the examination material available.