The Relationship Between Diameter and Wall Stress in Ascending Thoracic Aortic Aneurysms With a Tricuspid Aortic Valve

Abstract

Objective: Ascending thoracic aortic aneurysms (aTAAs) carry a risk of type A dissection. Elective repair guidelines were designed around diameter but fall short at capturing dissection risk in small aneurysms. Acute aortic events occur when wall stress exceeds wall strength. Patient-specific wall stress profiles may better predict aortic events. The purpose of this study was to compare the relation of diameter with wall stresses in aTAAs associated with a tricuspid aortic valve (TAV). Methods: Patients with TAV-aTAA diameter ≥ 4.0cm (n=230) were recruited and classified into 0.5cm long diameter groups. Three-dimensional aTAA geometries were reconstructed from ECG-gated computer tomography images. Finite element analyses were performed to simulate the cardiac cycle and determine wall stress profiles at systole. Peak stresses were compared with the Kruskal-Wallis test. Medians with interquartile ranges are reported. Results: TAV-aTAA longitudinal peak wall stress increased with diameter (p=2.7e-7). Longitudinal stresses were 291[266-325] kPa for size 4.0-4.4cm, 330[295-358] kPa for 4.5-4.9cm, 338[318-371] kPa for 5.0-5.4cm, 318[293-351] kPa for 5.5-5.9cm, and 373[363-449] kPa for ≥6.0cm. Circumferential peak wall stress increased with diameter (p=0.0006). Circumferential stresses were 460[419-526] kPa for size 4.0-4.4cm, 503[453-568] kPa for 4.5-4.9cm, 546[429-582] kPa for 5.0-5.4cm, 540[471-608] kPa for 5.5-5.9cm, and 596[507-649] kPa for ≥6.0cm (Figure) Conclusions: Circumferential and longitudinal wall stresses increase with diameter but the large overlap between groups limits diameter utility in risk stratification of aneurysms. Small aTAAs can experience stresses comparable to large aneurysms. Depending on wall strength, patient-specific wall stress may be a better predictor of acute aortic events.