Background and aim of the study: The three-dimensional motion of semilunar attachment of the leaflet ‘annulus’ remains obscure. It has been suggested that the aortic root is distensible and moves during the cardiac cycle. In the present study, the aortic root was evaluated using two dimensions. The aortic root, notably motion of the aortic annulus, was evaluated using multidetector computed tomography (MDCT), and a three-dimensional reconstruction of the aortic annulus was performed.
Methods: Twenty-five patients (17 males, eight females) underwent MDCT. None of the patients had aortic root disease, aortic valve disease, bicuspid valve, myocardial infarction or atrial fibrillation. The aortic annulus was measured in systole and diastole, and divided into three parts: the right coronary cusp (RCC), left coronary cusp (LCC) and non-coronary cusp (NCC). The lengths of the aortic annulus, sinus of Valsalva and sinotubular junction (STJ) were also measured in systole and diastole on longitudinal views.

Results: The lengths of each aortic annulus part in systole and diastole were as follows. In systole: RCC 41.8 ± 8.1 mm; LCC 39.3 ± 5.9 mm; NCC 43.7 ± 7.1 mm. In diastole: RCC 42.4 ± 7.0 mm; LCC 38.6 ± 7.8 mm; NCC 41.5 ± 7.8 mm. No statistically significant differences were observed between lengths in systole and diastole. The longitudinal lengths of aortic annulus, sinus of Valsalva and STJ at each period were as follows. In systole: aortic annulus 22.5 ± 2.2 mm; sinus of Valsalva 34.9 ± 4.3 mm; STJ 28.1 ± 3.2 mm. In diastole: aortic annulus 22.1 ± 2.2 mm; sinus of Valsalva 34.4 ± 4.7 mm; STJ 27.2 ± 3.1 mm. The length of the STJ in systole was significantly greater than that in diastole.
Conclusion: In the normal aortic root, no part of the aortic annulus changed length during the cardiac cycle. According to changes in aortic root dimensions, the commissures move outwards during the systolic phase.

The Journal of Heart Valve Disease 2006;15:617-621