Clarifying the anatomy of tetralogy of Fallot with S-shaped ascending aorta

Abstract

BackgroundWe have recently encountered several cases of tetralogy of Fallot with an abnormally oriented S-shaped ascending aorta. In this retrospective study, we sought to clarify the morphology of this unusual under-recognized variant of tetralogy of Fallot.MethodsWe reviewed our databases to identify all patients with tetralogy of Fallot having an S-shaped ascending aorta. We then used computed tomographic angiography to make a detailed assessment of the cardiac morphology.ResultsOut of the 21 patients we identified, 18 (86%) had a right aortic arch, 2 (9%) had a left aortic arch, and the remaining patient (5%) had a double aortic arch. Patients with right aortic arch, compared to those with the normally oriented ascending aorta, had lesser aortic override (29.3±14% vs 54.8±13.2%; p=0.0001) and a wider ascending aorta (2.52±0.7 cm vs 1.80±0.32; p=0.0003). Overall, compared to normal cases, the ascending aorta was located posteriorly, with a higher sterno-aortic distance (2.55±0.8 cm vs 0.99±0.45 cm; p=0.0001). The ascending aorta was longer (4.12±1.7 vs 3.07±0.82, p=0.03) although the tortuosity index (1.22±0.19 vs 1.15±0.17, p=0.23) was not different. Of the cases with right aortic arch and S-shaped ascending aorta, 16 (89%) had extrinsic compression of the right pulmonary artery (p = 0.0001), while 7 (39%) had crossed pulmonaryarteries(p = 0.008), with no such findings in those with normally oriented ascending aorta or those with left aortic arch and S-shaped ascending aorta.ConclusionTetralogy of Fallot with an S-shaped ascending aorta is a variant with lesser aortic override and a more posterior location of the aorta. Compression of the right pulmonary artery and crossed pulmonary arteries are frequent when the arrangement is associated with a right-sided aortic arch. These findings may have important implications for surgical management.