Fast Approximate Quantification of Endovascular Stent Graft Displacement Forces in the Bovine Aortic Arch Variant

Displacement forces (s) identify hostile landing zones for stent graft deployment in thoracic endovascular aortic repair (TEVAR). However, their use in TEVAR planning is hampered by the need for time-expensive computational fluid dynamics (CFD). We propose a novel fast-approximate computation of s merely exploiting aortic arch anatomy, as derived from the computed tomography (CT) and a measure of central aortic pressure.

We tested the fast-approximate approach against CFD gold-standard in 34 subjects with the "bovine" aortic arch variant. For each dataset, a 3-dimensional (3D) model of the aortic arch lumen was reconstructed from computed tomography angiography and CFD then employed to compute s within the aortic proximal landing zones. To quantify fast-approximate s, the wall shear stress contribution to the was neglected and blood pressure space-distribution was averaged on the entire aortic wall to reliably approximate the patient-specific central blood pressure. Also, values were normalized on the corresponding proximal landing zone area to obtain the equivalent surface traction ().

Fast-approximate approach consistently reflected (r²=0.99, p<0.0001) the pattern obtained by CFD, with a -1.1% and 0.7° bias in s magnitude and orientation, respectively. The normalized progressively increased (p<0.0001) from zone 0 to zone 3 regardless of the type of arch, with proximal landing zone 3 showing significantly greater forces than zone 2 (p<0.0001). Upon DF normalization to the corresponding aortic surface, fast-approximate was decoupled in blood pressure and a dimensionless shape vector (S) reflecting aortic arch morphology. showed a zone-specific pattern of orientation and proved a valid biomechanical blueprint of impact on the thoracic aortic wall.

Requiring only a few seconds and quantifying clinically relevant biomechanical parameters of proximal landing zones for arch TEVAR, our method suits the real preoperative decision-making process. It paves the way toward analyzing large population of patients and hence to define threshold values for a future patient-specific preoperative TEVAR planning.