Right-Sided Aortic Torsion in Patients with Abdominal Aortic Aneurysms

Altered flow dynamics within abdominal aortic aneurysms (AAA) may lead to changes in aneurysmal geometry, intraluminal thrombus (ILT) deposition, or aneurysmal progression. Aortic torsion is one geometric deviation that has been clinically observed but has not been formally evaluated in preoperative AAAs. This pilot retrospective cohort study investigates the degree and directionality of aortic torsion in patients with and without AAAs.

The inferior mesenteric artery (IMA angle) outlet angle was used to assess aortic torsion. Angles were measured with respect to the anterior-posterior (AP) axis in both aneurysmal (n = 370) and nonaneurysmal (n = 120) patients. Patient age, gender, maximum infrarenal aortic/AAA diameter (D_Max), and presence/percentage of ILT were calculated.

A total of 370 AAA patients (age: 74 [65:83], %male: 88%, D_Max: 50.1 mm [41.9-57.0 mm]) were retrospectively identified. ILT was present in 65% of cases and comprised 26.2% of the aneurysmal sac [18.6-36.7%]. Similarly, 120 patients without aneurysmal disease were identified (age: 70 [63:81], %male: 79%, D_Max: 23.3 mm [21.5-25.6]). The median IMA angle [25th-75th%] in the aneurysmal cohort was 17.0° [8.6°-25.3°] and closer to the AP axis compared to controls (38.5° [34.3°-44.9°], p < 0.001). Presence, percentage, and classification of ILT (r = 0.01, p = 0.93) had negligible impact on IMA outlet angle.

This study highlights the right-sided IMA preference in AAA patients compared to nonaneurysmal controls. The pathophysiology underlying this rotation may be associated with a right-sided helical flow pattern in expanding aneurysmal sacs. This sets the foundation for future investigations.