The prognostic impact of vascular calcification on abdominal aortic aneurysm progression

Abstract

Objective: The maximal aortic diameter is currently the only clinically applied predictor of abdominal aortic aneurysm (AAA) progression. It is known that the risk of rupture is associated with aneurysm size; hence, accurate monitoring of AAA expansion is crucial. Aneurysmal vessel wall calcification and its implication on AAA expansion are insufficiently explored. We evaluated the vascular calcification using longitudinal computed tomography angiographies (CTA) of patients with an AAA and its association with AAA growth.

Methods: We conducted a retrospective study of 102 patients with an AAA with a total of 389 abdominal CTAs at 6-month intervals, treated and followed at the Division of Vascular Surgery, Department of General Surgery, Medical University of Vienna. Digitally stored CTAs were reviewed for vascular calcification (volume and score) of the infrarenal aorta and common iliac arteries as well as for morphometric AAA analysis. In the prognostic setting, slow versus fast AAA progression was defined as a less than 2 mm or a 2-mm or greater increase in AAA diameter over 6 months. In addition, to analyze the association of vascular calcification and the AAA growth rate with longitudinal monitoring data, a specifically tailored log-linear mixed model was used.

Results: An inverse relation of increased abdominal vessel wall calcification and short-term AAA progression was detected. Compared with fast progressing AAA, the median calcification volume of the infrarenal aorta (1225.3 mm³ vs 519.8 mm³; P = .003), the median total calcification volume (2014.1 mm³ vs 1434.9 mm³; P = .008), and the median abdominal total customized Agatston calcium (cAC) score (1663.5 vs 718.4; P = .003) were significantly increased in slow progressing AAA. Importantly, a log-linear mixed model efficiently predicted AAA expansion based on current diameter and abdominal total cAC score (P = .042).

Conclusions: We assessed the prognostic value of CTA-measured vascular calcification for AAA progression. Increased vascular calcification stabilizes the aortic aneurysmal wall and likely protects against progressive AAA expansion, resulting in a significant decrease of aneurysm growth over time. As a consequence, this may have implications for rupture risk, mortality, morbidity, and cost.

Keywords: Abdominal aortic aneurysm; Calcification score; Calcification volume; Computed tomography angiography; Growth prediction; Vascular calcification.