In Vitro Reproduction of Device Deformation Leading to Thrombotic Complications and Failure of Flow Diversion

Abstract

<jats:p> Flow diverters (FDs) are increasingly used for complex intracranial aneurysms. As these self-expanding devices are deployed across an aneurysm neck, they can undergo deformations. The potential clinical consequences of FD deformations remain unclear. </jats:p><jats:p> We describe an immediate thrombotic complication attributed to a stereotypical stenotic deformation of an FD extremity that can occur when landing zones are of insufficient length. This case is supplemented with in vitro studies showing the relationship between i) the length of the landing zones and ii) discrepancies between the diameter of the device and recipient vessel, and the severity of FD stenosis. </jats:p><jats:p> In vitro, a shorter landing zone was associated with a progressive stenotic deformation of the terminal ends of all FDs studied. This deformation was more pronounced when the diameter of the device was oversized compared to the size of the recipient tube. In our clinical case, the presence of this deformation led to an immediate thrombotic complication, requiring deployment of a second stent to correct the observed stenosis. In addition, treatment failure ultimately led to a fatal rupture, a failure that can be explained by residual flows through a more porous transition zone, another characteristic FD deformation which occurs when they are oversized as compared to the parent vessel, but free to expand at the level of the aneurysm. </jats:p><jats:p> Proper selection of device diameter and length of the landing zone is important, and may decrease the incidence of deformation-related complications. </jats:p>

Republished: Late recurrence of a completely occluded large intracranial aneurysm treated with a Tubridge flow diverter

“…Several mechanisms underlying FDD recurrence or failure have been put forward: endoleak of the aneurysm sac11; FDD deformation leading to increased pore size and persistent blood entry into the aneurysm12; FDD deformation caused by inappropriate device diameter and length of the landing zone leading to deformation related complications; and failure of FDDs, which was proved by in vitro research 13…”

Virtual-versus-Real Implantation of Flow Diverters: Clinical Potential and Influence of Vascular Geometry

“…In addition, they observed a transition zone of variable porosity at the neck level associated with an inhomogeneous endothelial tissue colonization of the device scaffold, which could be associated with a treatment failure. Besides, Estrade et al 37 reported a case with very bad delayed outcomes related to implantation issues: A too-short landing zone and an oversized device induced a proximal conically deformed stent and a stenosis followed by immediate thromboembolic complications.…”

Tapered flow diverters in the treatment of intracranial aneurysms

“…In this transitional zone, metal coverage is lower, porosity is higher and on follow-up neointima formation is poor (14,16). In other words, as there is a direct relation between lower porosity of the 'free segment of the stent' (FSS) facing the aneurysm cavity and success of aneurysm occlusion (6,7), the increased porosity at TZ will result in sustained leak into the aneurysm and increase the risk of residual aneurysms after flow diversion (2,9,13,15,16). Focal zones of low porosity and residual flow specifically occur in curved segments or wide-neck aneurysms due to the deformation of the FD (8,13).…”

“…The discrepancy between the size of the landing zones will result in undersizing or oversizing of the device at either the proximal landing zone or the distal one based on what the operator chooses as his/her reference for the sizing of the flow diverter (16). Inevitably, there will be a conical transitional zone (TZ) between the fully expanded or even over expanded segment crossing the aneurysm and the relatively constrained distal or proximal landing zones (9). In this transitional zone, metal coverage is lower, porosity is higher and on follow-up neointima formation is poor (14,16).…”