Cardiac Pulsatility– and Respiratory-Induced Deformations of the Renal Arteries and Snorkel Stents After Snorkel Endovascular Aneurysm Sealing

Abstract

Purpose: To quantify deformations of renal arteries and snorkel stents after snorkel endovascular aneurysm sealing (Sn-EVAS) resulting from cardiac pulsatility and respiration and compare these deformations to patients with untreated abdominal aortic aneurysms (AAA) and snorkel endovascular aneurysm repair (Sn-EVAR). Materials and Methods: Ten Sn-EVAS patients (mean age 75±6 years; 8 men) were scanned with cardiac-gated, respiration-resolved computed tomography angiography. From 3-dimensional geometric models, changes in renal artery and stent angulation and curvature due to cardiac pulsatility and respiration were quantified. Respiration-induced motions were compared with those of 16 previously reported untreated AAA patients and 11 Sn-EVAR patients. Results: Renal artery bending at the stent end was greater for respiratory vs cardiac influences (6°±7° vs −1°±2°, p<0.025). Respiration caused a 3-fold greater deformation on the left renal artery as compared with the right side. Maximum curvature change was higher for respiratory vs cardiac influences (0.49±0.29 vs 0.24±0.17 cm−1, p<0.025), and snorkel renal stents experienced similar maximum curvature change due to cardiac pulsatility and respiration (0.14±0.10 vs 0.19±0.09 cm−1, p=0.142). When comparing the 3 patient cohorts for respiratory-induced deformation, there was significant renal branch angulation in untreated AAAs, but not in Sn-EVAR or Sn-EVAS, and there was significant bending at the stent end in Sn-EVAR and Sn-EVAS. Maximum curvature change due to respiration was ~10-fold greater in Sn-EVAR and Sn-EVAS compared to untreated AAAs. Conclusion: The findings suggest that cardiac and respiratory influences may challenge the mechanical durability of snorkel stents of Sn-EVAS; similarly, however, respiration may be the primary culprit for tissue irritation, increasing the risk for stent-end thrombosis, especially in the left renal artery. The bending stiffness of snorkel stents in both the Sn-EVAR and Sn-EVAS cohorts damped renal branch angulation while it intensified bending of the artery distal to the snorkel stent. Understanding these device-to-artery interactions is critical as they may affect mechanical durability of branch stents and quality and durability of treatment.

Impact of renal chimney intra-aortic stent length on branch and end-stent angle in chimney endovascular aneurysm repair and endovascular aneurysm sealing configurations

“…Previous analyses of cardiac pulsatility and respiratory-induced deformations of the renal arteries after complex EVAR showed bending stiffness of chimney stents dampened renal branch angulation, whereas it intensified bending of the renal arteries distal to the chimney stent. 8,12 Indeed, one previous biomechanical analysis observed both chEVAR and chEVAS patients experienced approximately 10 times as much maximum bending of the renal arteries compared to a similar cohort with untreated AAAs. 12 While these findings were again noted in the present analysis, we also noted distinct differences between chEVAR and chEVAS procedures.…”

“…8,12 Indeed, one previous biomechanical analysis observed both chEVAR and chEVAS patients experienced approximately 10 times as much maximum bending of the renal arteries compared to a similar cohort with untreated AAAs. 12 While these findings were again noted in the present analysis, we also noted distinct differences between chEVAR and chEVAS procedures. Renal chimney stents were notably longer in the chEVAR group compared to the chEVAS group.…”

“…In addition, the non-significant trend toward decreased branch angle and end-stent angle among chEVAS patients compared to chEVAR patients supports previous findings that peak curvature and maximum curvature change locations were more proximal in chEVAS patients, an observation that suggests bending concentrated nearer to the renal ostium is related to the less-complaint nature of the sac-filling polymer. 12…”

“…Details regarding CTA image acquisition and processing methods have been described in the previous studies. 7,9,12 Using dedicated modeling software (SimVascular; Open Source Medical Software Corporation, San Diego, CA, USA), initial postoperative CTA images were utilized to generate three-dimensional geometric models of the abdominal aorta with branch vessels, branch vessel stents, and aortic endografts (Figure 1). Imaging was acquired at inspiratory breath-hold.…”

“…Previous work has explored this topic as it relates to cardiac pulsatility-, respiratory-, and EVAR-induced deformations of the renal arteries associated with complex EVAR. 7–12…”