Geometric Analysis of Aortic Arch for Patients with Type B Aortic Dissection

Background: Endovascular management of aortic arch is always demanding and challenging in type B aortic dissection (TBAD) patients. However, there is limited knowledge to understand the complex geometry of aortic arch. The aim of this study is to investigate aortic arch geometry and its potential clinical implications for endovascular planning. Methods: A total of 175 TBAD patients with preoperative computed tomography angiogram images were evaluated. 3Mensio Vascular software was used to measure the length, tortuosity index (TI), and tortuosity angle of proximal aorta, which was divided into Zone to Zone 3 according to Ishimaru's arch map. TI was used to evaluate the tortuosity of total proximal aorta, and maximal tortuosity angle within each landing zone (LZ) was represented the local aortic segment tortuosity. Potential factors interfering with geometry (age, body mass index, sex, arch type, hypertension, and dissection chronicity) were evaluated by univariate and multivariate regression analysis. Results: The mean age of patients was 52 years. The length (mean +/- standard deviation [SD]) was 87.83 +/- 11.34 mm in Zone 0, 11.09 +/- 3.94 mm in Zone 1, and 15.05 +/- 4.45 mm in Zone 2. TI of total proximal aorta (from Zone 0 to Zone 3) was 1.27 +/- 0.076 (mean +/- SD). The mean maximal tortuosity angle (+/- SD) of Zones 0e3 was 28.53 +/- 5.40 degrees, 24.59 +/- 9.20 degrees, 31.32 +/- 8.78 degrees, and 31.4 +/- 8.85 degrees, respectively. Main variations of tortuosity in relation to age and arch type were identified. With age-related development, each LZ becomes less tortuous (all P < 0.05). Across arch types Ito III the tortuosity of Zones 2 and 3 increased significantly, in direct contrast to the decreasing trend of Zones 0 and 1 (all P < 0.005). Conclusions: Aortic arch geometry varies significantly across type I to type III arch in TBAD patients. Zones 2 and 3 in arch type III and Zones 0 and 1 in arch type I, seem to be the unfavorable LZs choice due to more tortuosity.