Assessment of abdominal aortic aneurysm wall distensibility with electrocardiography-gated computed tomography

Background: Despite the fact that abdominal aortic aneurysm (AAA) is asymptomatic in the vast majority of cases, sudden rupture with a fatal outcome may still occur. Early planned resection or endovascular aneurysm repair of small AAAs may help prevent a rupture, but both methods are associated with significant mortality. The aim of our study was to determine AAA wall distensibility and to compare it with distensibility of the "healthy" aorta of the same patient.

Methods: We evaluated 12 patients with AAA, mean age of 65 years, 10 men and 2 women. The mean diameter of the aneurysm was 5.95 cm.

Results: We did not find any correlation between aneurysm diameter and any of the following parameters: (1) distensibility of AAA wall (p = 0.8119), (2) distensibility of AAA lumen (p = 0.1262), and (3) distensibility of normal aorta (p = 0.9828). We proved by use of the Wilcoxon test that distensibility of the wall of the normal aorta is significantly greater than distensibility of the AAA wall (p = 0.0141). A significant difference between distensibility of the AAA wall and AAA lumen was proved (p = 0.0221) also by use of the Wilcoxon test. Distensibility of the AAA wall is significantly lower. Despite the proved significant differences between distensibility of the AAA wall and normal aorta, values of AAA wall distensibility nearly reached values of distensibility of the normal aorta above the AAA in some particular cases; the value was even higher in one case. We observed this phenomenon in four patients of our small population, two of them suffering from rapidly increasing aneurysm.

Conclusion: In our opinion, electrocardiography-synchronized computed tomographic angiography may contribute to diagnostics in the future. Lumen distensibility is significantly higher than distensibility of the wall. The thrombus acts in this respect as a buffer, thus inhibiting the effect of pulse waves on the wall. From a mechanical point of view, the thrombus rather acts protectively against the risk of rupture. Distensibility assessment could be another fragment of the diagnostic algorithm and decision making on intervention.