Longitudinal Stent Deformation in Undeployed Stents: A Case Series

Longitudinal stent deformation (LSD) is a recently reported problem with newer generation stents. The modification of stent materials and designs to make them more deliverable and conformable, as well as a focused approach in retaining their radial strength, has compromised longitudinal strength in currently available stents. Additionally, enhanced stent radiopacity, improved fluoroscopy, and heightened awareness have led to an increased incidence rate of the potentially under-recognized problem of LSD. Although originally described in deployed stents, LSD is being recognized in undeployed stents too. With available data to suggest an increased rate of adverse cardiac events like stent thrombosis and in-stent restenosis with LSD in deployed stents, an attempt to retrieve an undeployed deformed stent appears justified. We report 3 cases of LSD in undeployed stents and discuss its recognition. We also discuss the retrieval and visual inspection of retrieved stents and the simultaneous completion of coronary interventions via a double guide technique.

397 Long-term follow-up after balloon expandable covered stents implantation for management of TAVI-related vascular access complications

Aims Despite increasing experience and device innovation with transcatheter aortic valve implantation (TAVI), vascular complications are still a major problem and endovascular management is generally the first option. When stent implantation is required, self expandable (SE) stents are generally preferred over balloon expandable (BE) stents as they are more elastic and less compressible. However, BE stents support higher radial outward force, adhere to the vase lumen with greater precision and are less expensive. As no large registry reported data about stents BE alone in this setting, we report our experience with BE stents implantation to manage a vascular complication after TAVI. We believe that our work could be useful and possibly serves as a starting point for future research. Methods and results We retrospectively collected baseline, procedural and follow-up data about 78 patients who were implanted with a BE stent to manage a vascular complication after TAVI. At a median clinical follow-up of 410 days (IQR: 66–1016 days), no percutaneous or surgical interventions were reported after discharge. No cases of symptomatic leg-ischaemia were reported and only one patient was symptomatic for claudication. Doppler follow-up (available for 25 patients; 32%) showed no cases of stent fracture or displacement. Conclusions Our experience showed good acute and long-term results of BE covered stent implantation to manage a vascular complication after TAVI. It is possible that a greater radial outward force is a good choice in terms of hemostasis without necessarily being associated with stent deformation/fracture resulting in restenosis or further interventions. While present data may not be generalized, they may be useful to critically re-evaluate (and eventually reduce) the need of SE stents when treating femoral arteries bleedings.

Fluid-Structure Interaction in Coronary Stents: A Discrete Multiphysics Approach

Stenting is a common method for treating atherosclerosis. A metal or polymer stent is deployed to open the stenosed artery or vein. After the stent is deployed, the blood flow dynamics influence the mechanics by compressing and expanding the structure. If the stent does not respond properly to the resulting stress, vascular wall injury or re-stenosis can occur. In this work, a Discrete Multiphysics modelling approach is used to study the mechanical deformation of the coronary stent and its relationship with the blood flow dynamics. The major parameters responsible for deforming the stent are sorted in terms of dimensionless numbers and a relationship between the elastic forces in the stent and pressure forces in the fluid is established. The blood flow and the stiffness of the stent material contribute significantly to the stent deformation and affect its rate of deformation. The stress distribution in the stent is not uniform with the higher stresses occurring at the nodes of the structure. From the relationship (correlation) between the elastic force and the pressure force, depending on the type of material used for the stent, the model can be used to predict whether the stent is at risk of fracture or not after deployment.

Fluid-Structure Interaction in Coronary Stents: a Discrete Multiphysics Approach

Stenting is a common method for treating atherosclerosis. A metal or polymer stent is deployed to open the stenosed artery or vein. After the stent is deployed, the blood flow dynamics influence the mechanics by compressing and expanding the structure. If the stent does not respond properly to the resulting stress, vascular wall injury or re-stenosis can occur. In this work, Discrete Multiphysics is used to study the mechanical deformation of the coronary stent and its relationship with the blood flow dynamics. The major parameters responsible for deforming the stent are sort in terms of dimensionless numbers and a relationship between the elastic forces in the stent and pressure forces in the fluid is established. The blood flow and the stiffness of the stent material contribute significantly to the stent deformation and affect the rate of deformation. The stress distribution in the stent is not uniform with the higher stresses occurring at the nodes of the structure.

A bile duct stent broken during repeat pregnancy in a post-liver transplant patient

A young female patient who developed anastomotic biliary stricture following an orthotopic liver transplantation was observed. A self-expandable metallic stent was placed to correct the stricture. At the 8th month of her repeat pregnancy, the stent broke asymptomatically into half. Fortunately, the second childbirth, like the first one, had no complications. Eighteen months later, due to obstruction of fragments by sludge and gallstones, re-stenting was performed with a coated biliary stent. Four years and five months later, recurrent jaundice occurred due to occlusion of the second stent. This was addressed by surgical removal of both stents. Two years after surgery, the bile ducts remain completely patent. We found only two cases in literature on a similar extremely rare biliary stenting complication. It has been suggested that stent deformation may be related to pregnancy. The feasibility of using stenting in benign biliary strictures in some clinical situations is discussed.

Reverse longitudinal stent deformation during percutaneous intervention via the retrograde approach to a chronic total occlusion of the right coronary artery: a case report

Background Longitudinal stent deformation (LSD) is an uncommon but recognized mechanical complication of coronary stent implantation, usually occurring at the proximal stent edge due to compression by guide catheter or catheter extensions. Retrograde techniques for chronic total occlusion (CTO) percutaneous coronary intervention expose the distal stent edge to potential interaction with retrograde equipment under a tensioned system. Case summary We describe a case of distal stent edge LSD, occurring during a retrograde approach to a right coronary artery CTO via septal collateral channels. While removing the externalized wire, interaction with the retrograde microcatheter caused compression of the distal end of the newly implanted stents. Discussion This unusual complication highlights the reduced longitudinal strength of newer generation stent platforms and the risks of interaction between retrograde equipment and stents on an externalized wire.

Bioengineering Case Study to Evaluate Complications of Adverse Anatomy of Aortic Root in Transcatheter Aortic Valve Replacement: Combining Biomechanical Modelling with CT Imaging

Gated computed tomography (CT) might not adequately predict occurrence of post-implantation transcatheter aortic valve replacement (TAVR) complications in hostile aortic root as it would require a more complex integration of morphological, functional and hemodynamical parameters. We used a computational framework based on finite element analysis (FEA) to simulate patient-specific implantation. Application of biomechanical modelling using FEA to gated-CT was able to demonstrate the relation of the device with voluminous calcification, its consequent misalignment and a significant stent deformation. Use of FEA and other advanced computed predictive modelling techniques as an adjunct to CT scan could improve our understanding of TAVR, potentially predict complications and fate of the devices after implantation and inform patient-specific treatment.

Evaluation of the Accero Stent for Stent-Assisted Coiling of Unruptured Wide-Necked Intracranial Aneurysm Treatment with Short-Term Follow-Up

Background: Stent-assisted coiling is an effective method of treating intracranial aneurysms. The aim of the study was to assess the safety and efficacy of the new Accero stent for the treatment of intracranial aneurysms. Materials and Methods: It was a retrospective, single-center study. Eighteen unruptured intracranial aneurysms were treated using the stent-assisted coiling method with the Accero stent. Patient demographics, aneurysm characteristics, procedural parameters, grade of occlusion, complications, and clinical results were analyzed. Follow-up magnetic resonance (MR) was performed 6 months after intervention. Results: Seventeen patients with 18 incidental unruptured aneurysms were electively treated with coiling and the Accero stent. The aneurysms were located on internal carotid artery (ICA), middle cerebral artery (MCA) and basilar artery (BA). All stents were deployed successfully. Immediate complete occlusion rate Raymond-Roy occlusion classification (RROC) class I was achieved in 13 cases and class II in 4 cases. Complications occurred in 2/17 treatments and included guidewire stent perforation with subarachnoid hemorrhage (SAH) and stent deformation. Vascular spasm in the subarachnoid hemorrhage (SAH) patient subsided before discharge. Ninety days after intervention, the modified Rankin Scale (mRS) value was 0. RROC class I was observed in 88.23% of cases in follow-up. Conclusion: The Accero stent provides excellent support for coil mass. It constitutes an efficacious device with good initial occlusion rate for treating wide-necked unruptured intracranial aneurysms.