A comprehensive analysis of the normal aortic root using 4D computed tomography

Abstract Background A precise analysis of the aortic valve and aortic root are essential for valve-sparing surgeries. Preoperative assessment primarily relies on echocardiography. In order to achieve more accurate evaluation, cardiac computed tomography (CT) has emerged as a complementary tool for root analysis. We have previously introduced a novel analysis technique based on 4D (3D+ time) imaging of the normal aortic root. Purpose This study aims to evaluate the dimensions and dynamic changes of the normal aortic root in adult patients using 4D CT. Methods Using in-house software, 140 cardiac CT of adult patients with a normally functioning tricuspid aortic valve (mean gradient 15 mmHg, less than 1+ aortic regurgitation on echocardiography) were retrospectively analyzed. A dynamic study of the aortic annulus and other planes of the aortic root was conducted across all 10 temporal phases of the cardiac cycle. Leaflet dimensions were calculated in mid-diastole. Results The mean age was 59 ± 14 yrs, with 63% being males. The mean geometric height was 17.5 ± 1.9 mm, the mean effective height was 8.3 ± 1 mm, the mean coaptation height was 4.5 ± 0.7 mm, and the mean commissural height was 23.8 ± 3.7 mm. Compared to the left and non-coronary leaflets, the right leaflet exhibited the lowest geometric height (17.1 ± 1.9 mm vs 17.6 ± 2.1 mm and 17.7 ± 1.9 mm, p 0.001) but the longest free margin (29.1 ± 3.5 mm vs 28.1 ± 3.4 mm and 28.5 ± 3.6 mm, p 0.001). A positive correlation was observed between the aortic annulus size and the dimensions of the virtual basal ring (VBR), Valsalva sinuses, sinotubular junction (STJ), free margin and geometric height (r= 0.53, 0.81, 0.84, 0.88, 0.67, respectively, p0.0001). Figure 1 illustrates the normalization of root dimensions in relation to the VBR (A) and to the geometric height (B). Dynamic analysis revealed a progressive expansion of the aortic root beginning at the level of the VBR (area expansion of 22.1 ± 6.1%), sequentially followed by the aortic annulus (13.2 ± 4.6%), Valsalva sinuses (16.1 ± 7.6%), and STJ (16.4 ± 5.4 %) (Figure 2). During systole, the aortic annulus become more circular (Eccentricity index of 0.45 ± 0.08 in systole vs 0.52 ± 0.09 in diastole, p 0.001). The planes of VBR and STJ also become more distant (24.33 ± 2 mm in systole vs 23.73 ± 2.17 mm, p=0.04) but more parallel (7.1° ± 2.8 in systole vs 8.9° ± 3.5 in diastole, p0.001) to one another lining up the outflow tract with the ascending aorta. Conclusion This study presents a comprehensive analysis of the dimensions and the dynamics of the normal aortic root. These results can serve as a reference for valve analysis in aortic regurgitation and hence guide a dynamical approach for valve-sparing surgeries.Normalization of root dimensions