Acute type A aortic dissection in bicuspid versus tricuspid aortic valve patients: focus on geometrical features of the aorta

OBJECTIVES: This retrospective observational study aimed to assess the geometrical features, including diameters, length and angulation, of the ascending aorta with bicuspid and tricuspid aortic valve and to identify imaging markers potentially predicting whether aortopathy is likely to evolve chronically or to complicate with acute type A dissection. METHODS: Angio-computed-tomography scans of 354 patients (from 3 centres) with non-dilated (n = 97), aneurysmal (n = 100) or dissected aorta (n = 157) were reviewed. Diameters were measured at root, sinotubular junction, ascending, brachio-cephalic trunk origin; centreline lengths of the root and tubular tract and ascending-arch angle (between the ascending tubular tract axis and the proximal arch axis) were also measured. For 12 dissection patients, pre-dissection scans were available to investigate predisposing aortic geometry. Statistical analysis included: tricuspid versus bicuspid comparisons in each subgroup; univariate and multivariate analyses of the predictors of ascending-arch angle narrowing; and estimation of diagnostic accuracy of the angle parameter. RESULTS: Diameters and lengths were similar between aneurysms and dissections, whereas dissections showed a significant ascending arch angle narrowing (117 +/- 13 degrees in tricuspid, 115 +/- 14 degrees in bicuspid) compared to non-dilated and aneurysmal aortas (all P < 0.001). The best angle cut-off to discriminate dissection patients was 131 degrees (96% sensitivity). In patients with a pre-dissection scan, Asc-Arch narrowing was already present before dissection. In non-dissected aortas over-angulation was predicted by root phenotype dilatation both in bicuspid and tricuspid patients. Bicuspid patients with non-dilated aorta showed elongated root (P = 0.027), a feature significantly correlated with Asc-Arch angle narrowing (P = 0.008). CONCLUSIONS: The ascending-arch angle is promising as a risk marker for dissection to be used along with diameter. Its narrowing seems to be associated with elongation of the root, a feature that bicuspid patients can show even without significant dilatation. Root phenotype aortopathy may be at higher risk also with tricuspid aortic valve.