Research Article: Tortuosity of the descending thoracic aorta: Normal values by age

Date Published: April 23, 2019

Publisher: Public Library of Science

Author(s): Viony M. Belvroy, Hector W.L. de Beaufort, Joost A. van Herwaarden, Jean Bismuth, Frans L. Moll, Santi Trimarchi, Rudolf Kirchmair.

http://doi.org/10.1371/journal.pone.0215549

Abstract

Aging changes the aorta in length, tortuosity and diameter. This is relevant in thoracic endovascular aortic repair (TEVAR) and in the long term follow up.

Two groups of hundred patients < 65 years and hundred patients ≥ 65 years, with no vascular diseases were made. Thin cut CT scans were analyzed with 3Mensio Vascular software and the following measurements were collected; tortuosity index, curvature ratio, maximum tortuosity in degrees and the level of vertebrae of the maximum tortuosity. The descending thoracic aorta (DTA) was analyzed and was divided into four zones of equal length. Subjects were divided into three groups based on their maximum tortuosity value: low (< 30°), moderate (30° – 60°) and high (> 60°). A linear regression model was built to test the effect of age and gender on tortuosity. Tortuosity was more pronounced in the ≥ 65 compared to the < 65 group (tortuosity index: 1.05 vs. 1.14, respectively; p < 0.001), curvature ratio (1.00 vs. 1.01; p < 0.001), maximum tortuosity (22.24 vs. 27.26; p < 0.001), and group of angulation (low vs. low; p < 0.001). Additionally, the location of maximum tortuosity was further distal for the ≥ 65 group (level of vertebrae; 5.00 vs. 5.00; p < 0.001), and zone of maximum tortuosity (4A vs. 4A; p < 0.001). There was no significant difference between male and female subjects. Normal DTA tortuosity increases with age. This is important to understand natural aging and for TEVAR planning and follow-up.

Partial Text

As every stent graft has a fixed length and diameter, which allows only some oversizing, it is important to understand how the aorta changes in length, tortuosity and diameter during follow-up after thoracic endovascular aortic repair (TEVAR). This inevitable process of ageing may sabotage the initial excellent endovascular results. Hence, more knowledge about this physiological phenomenon might help to improve stent grafts designs in order to create durable results of endovascular repairs.

The patients were split into two groups of 100 patients. The < 65y patients had a mean age of 50.9 years old and the ≥ 65y patients had a mean age of 77.9 years old. The type of arch was measured in all patients, type 1 (< 65y = 66; ≥ 65y = 38), type 2 (<65y = 30; ≥ 65y = 43) and type 3 (< 65y = 4; ≥ 65y = 19), see Fig 5. The mean length of the centerline differs between the groups (< 65y = 190.7cm vs. ≥ 65y = 212.5cm; 0.000), see Table 1. The differences were measured between the < 65y and ≥ 65y patients in tortuosity index (1.05 vs. 1.14; p = 0.000), curvature ratio (1.00 vs. 1.01; p = 0.000), maximum tortuosity in degrees (22.24 vs. 27.26; p = 0.000), the level of vertebrae of the maximum tortuosity (5.00 vs. 5.00; p = 0.001), the zone of maximum tortuosity (4A vs. 4A; p = 0,000), and the groups of angulation (low vs. low; p = 0,000). For an overview see Table 2 and Fig 6. The physiological effect of aging on the DTA is inevitable. Knowing that the aorta becomes more tortuous and longer with age can help to improve future generations of stent grafts to obtain less complications and better outcomes.   Source: http://doi.org/10.1371/journal.pone.0215549

 

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