Arterial tortuosity in genetic arteriopathies

Abstract

Purpose of review: Arterial tortuosity is emerging as a common feature in genetically mediated thoracic aortic disease that may be prognostic. This review will summarize recent literature on arterial tortuosity in the setting of genetic arteriopathies.

Recent findings: Although arterial tortuosity has been primarily described in Loeys-Dietz syndrome due to TGFBR1 and TGFBR2 mutations and in arterial tortuosity syndrome due to SLC210A mutations, recent studies that use quantitative measures of tortuosity suggest that tortuosity is present in many other genetic conditions associated with aortic dilation and dissection. The mechanisms of the development of tortuosity in these disorders are not fully understood, but are founded in the concept that there is abnormal, pathologic arterial lengthening in a fixed space, resulting in more tortuous vessels. Further studies suggest that patients with increased arterial tortuosity are at increased risk of adverse cardiovascular events, including aortic surgery, aortic dissection, and death.

Summary: Arterial tortuosity is commonly present in genetically mediated aortic disease. Given the suboptimal performance of aortic dimension alone in predicting aortic dissection, quantification of tortuosity may augment the current algorithms for determining risk in patients with aortic disease.

Figure 1

Examples of vertebral artery tortuosity in Marfan syndrome with FBN1 mutation (A) and Loeys-Dietz syndrome with a TGFBR2 mutation (B).

Figure 2

Calculating the vertebral artery tortuosity index (VTI). This example uses a volume-rendered 3D magnetic resonance angiogram. Actual length (A and C) and straight length (B and D) of each vertebral artery are measured from the origin of vessel to the vertebral level C2 before the normal posteriolateral bend of the vessel. For both vertebral arteries, the distance factor is calculated: (actual/straight length−1)*100. The maximum distance factor of the two vessels is the VTI. In this example of a patient with Loeys-Dietz syndrome, the left vertebral artery distance factor is ((131.1/83.6)−1)*100=57. This can be thought of as 57% excess length of the vessel. The right distance factor is ((108.6/73.0)−1)*100=49, or 49% excess length. Therefore this patient’s VTI is 57%. Images complements of Alex Dodd, Texas Children’s Hospital.

Figure 3

Calculating the aortic tortuosity index (ATI), per Franken et al., International Journal of Cardiology 2015 from a 3D computed tomography angiogram. ATI is calculated as the ratio of aortic length (actual length) to geometric length (straight length). The aortic length (left side of image) was defined as the length of a centerline through the entire aorta (from annulus to aortic bifurcation) created by manually placed seeding points through the lumen of the aorta using post-processing software. Geometric length is the Cartesian distance between its 2 endpoints (added in smaller image on right, overlying the centerline). Aortic tortuosity index (ATI) is measured by dividing aortic length by geometric length. In this example in a patient with significant aortic tortuosity, aortic length = 367.2 mm, geometric length = 174.9 mm, ATI = 2.10. Images complements of Alex Dodd, Texas Children’s Hospital.