Morphological modification of the aortic annulus in tricuspid and bicuspid valves after aortic valve reimplantation: an electrocardiography-gated computed tomography study†

OBJECTIVES: Aortic valve-sparing operations have been shown to produce fewer valve-related complications than valve replacement. The aortic root is a morphological and functional unit in which the annulus plays an important role on dynamism, shape and geometry of the valve with different results in bicuspid aortic valves (BAVs) or tricuspid aortic valves (TAVs). The aim is to evaluate the differences in the size and shape of the aortic annulus between native BAVs and TAVs using ECG-gated computed tomography (CT) after a reimplantation procedure. METHODS: We selected 35 patients scheduled for aortic valve reimplantation who underwent good-quality preoperative and postoperative ECG-gated contrast-enhanced CT scan of the aortic root. Twenty-three patients had TAV, 8 patients type 1 BAV and 4 patients type 0 BAV. Major diameter and minor diameter, perimeter (P) and area (A) were measured. The shape of the aortic annulus was considered 'circular' or 'elliptic' according to the Ellipticity Index. We also selected a subgroup of 18 patients (9 TAVs and 9 BAVs) to evaluate annular shape and size variations through the cardiac cycle and to study the expansibility both in the preoperative and in the postoperative phases. RESULTS: Preoperative CT scans showed an elliptic shape of TAVs (Ellipticity Index 1.3 ± 0.1), a circular shape of type 0 BAVs (1.1 ± 0.1) and an intermediate behaviour of type 1 BAVs, suggesting a possible gradual spectrum of circularity from TAVs to type 1 BAVs to type 0 BAVs. Postoperative CT scans did not show any significant difference in annular shape among the 3 groups, which demonstated a similar roundness, obviating the preoperative differences. Analysing the expansibility of the aortic annulus during the cardiac cycle, we observed that it was completely absent in the preoperative phase in BAVs, while in the postoperative phase, both TAVs and BAVs showed a small but similar expansibility after the annular reduction. CONCLUSIONS: There is a possible gradual spectrum in terms of shape, from native TAVs, to type 1 BAVS to type 0 BAVs. These differences are eliminated in the postoperative phase, suggesting an active role of the annuloplasty on the geometry of the aortic annulus. The preoperative analysis showed a complete inelasticity of BAVs, which was partly restored in the postoperative phase.