Tortuosity of the Descending Thoracic Aorta in Patients with Aneurysm and Type B Dissection: A Quantitative Analysis

Introduction: Tortuosity in the descending thoracic aorta is becoming more important since thoracic endovascular aortic repair (TEVAR) is the gold standard for treating thoracic aortic disease. The literature reports that tortuosity has an influence on the occurrence of endoleaks1. There is some literature defining the angulation and tortuosity of the aortic arch. Recently, a new classification has been published, an extended version of the Ishimaru classification of the four landing zones in the aortic arch2,3. However, zone 4 of the Ishimaru classification and further distally have not been well described yet. The general insight is that tortuosity comes with aging in the descending thoracic aorta. With this report we want to define and classify the tortuosity in the diseased descending thoracic aorta. Methods: A total number of two hundred seven patients were divided into three groups. Sixty-nine healthy patients, with no vascular diseases, were compared with sixty-nine patients with descending thoracic aneurysm (DTA) and sixty-nine patients with type B aortic dissection (TBD). CTA scans, with thin cut slices (1.0 or 1.5 mm) were analyzed with 3Mensio Vascular software and the following measurements were collected; tortuosity index (length of the centre lumen line divided by the true length), curvature ratio (outer curvature length divided by length centre lumen line), the maximum and minimum angulation in degrees of the descending thoracic aorta and the level of vertebrae of the maximum and minimum angulation. The descending thoracic aorta was analyzed from two cm distal to the Left Subclavian Artery up to the Celiac Trunk and was divided into four zones of equal length, from proximal to distal, numbered one to four. Additionally, the maximum angulation was divided into three groups: low (< 30°), moderate (30° – 60°) and high angulation (> 60°). Results: The mean age of the Healthy group (HG) was 68.3 years old, in the Aneurysm group (AG) 72.2 and in the Dissection group (DG) 64.1. Compared to the HG, tortuosity was more pronounced in the DG, and even more in the AG, as evidenced by the tortuosity index (1.11 vs. 1.20 vs. 1.31, respectively; p < 0.001), curvature ratio (1.00 vs. 1.01 vs. 1.03; p < 0.001), maximum angulation in degrees (28.17 vs. 33.29 vs. 43.83; p < 0.001), and group of angulation (1.00 vs. 2.00 vs. 1.00; p < 0.001). Additionally, compared to HG, the location of maximum angulation was further distal for the DG and even further in the AG, as evidenced by the vertebral level of maximum angulation (5.00 vs. 7.00 vs. 8.00; p < 0.001), and zone of maximum angulation (1.00 vs. 2.00 vs. 2.00; p < 0.001). Conclusion: This study shows that tortuosity in the descending thoracic aorta becomes even more prominent in diseased aortas, especially for patients with aneurysmal diseases. The upcoming endovascular technology and interventions have to handle with this phenomenon in order to prevent aortic complications and to obtain positive long-term outcome. References1.Nakatamari H, Ueda T, Ishioka F, et al. Discriminant analysis of native thoracic aortic curvature: risk prediction for endoleak formation after thoracic endovascular aortic repair. J Vasc Interv Radiol. 2011;22(7):974-979.e2. doi:10.1016/j.jvir.2011.02.0312.Marrocco-Trischitta MM, de Beaufort HW, Secchi F, et al. A geometric reappraisal of proximal landing zones for thoracic endovascular aortic repair according to aortic arch types. J Vasc Surg. 2017;65(6):1584-1590. doi:10.1016/j.jvs.2016.10.1133.Ishimaru S. Endografting of the Aortic Arch. J Endovasc Ther. 2004;11(SupplementII):II-62-II-71. doi:10.1583/04-1407.1