Bovine Aortic Arch: A Result of Chance or Mandate of Inheritance?

Abstract

Previous studies have shown that bovine arch incidence is higher in patients with thoracic aortic aneurysms than in patients without an aneurysm. Although thoracic aortic aneurysm disease is known to be familial in some cases, it remains unknown if bovine arch results from a genetic mutation, thus allowing it to be inherited. Our objective was to determine the heritability of bovine arch from phenotypic pedigrees. We identified 24 probands from an institutional database of 202 living patients with bovine arch who had previously been diagnosed with thoracic aortic aneurysm and who had family members with previous chest computed tomography or magnetic resonance imaging scans. Aortic arch configuration of all first-degree and second-degree relatives was determined from available scans. Heritability of bovine arch was estimated using maximum-likelihood-based variance decomposition methodology implemented by way of the SOLAR package (University of Maryland, Catonsville, Maryland). 43 relatives of 24 probands with bovine arch had preexisting imaging available for review. The prevalence of bovine arch in relatives with chest imaging was 53% (n = 23) and did not differ significantly by gender (male: 64.3%, female: 55.6%, p = 1). The bovine arch was shown to be highly heritable with a heritability estimate (h²) of 0.71 (p = 0.048). In conclusion, the high heritability of bovine arch in our sample population suggests a genetic basis.

Figure 1.

(A) Illustration of Type 1 (left) and Type 2 BA (right). [Reproduced with permission from Hornick M, Moomiaie R, Mojibian H, Ziganshin B, Almuwaqqat Z, Lee ES, Rizzo JA, Tranquilli M and Elefteriades JA. ‘Bovine’ aortic arch - a marker for thoracic aortic disease. Cardiology. 2012;123:116-24.] (B) Representative computed tomography imaging of Type 1 (top) and Type 2 BA (bottom) in coronal, axial, and 3-dimensional (3D) reconstruction views. An aberrant left vertebral artery (star) is also noted in the example of Type 1 BA. Innominate artery (circle), left common carotid artery (‘X’).

Figure 2.

Selected pedigrees for bovine arch and thoracic aortic aneurysm. The presence of a bovine arch was determined from imaging, whereas a thoracic aortic aneurysm was self-reported. Shading indicates the presence of a bovine arch (left) and a thoracic aortic aneurysm (right). Question mark (‘?’) indicates unknown arch configuration because of the absence of imaging. Offspring of subjects only shown when at least 1 had available imaging. The p values are derived from the binomial test, assuming a population prevalence for the bovine arch of 27%.