Abstract W MP8: Stent Retrievers Do Not Encase Clots But Hook Them Within Seconds
Introduction: Stent retriever procedures for clot removal in proximal cerebral arteries are often assumed to securely encase a clot for withdrawal.
Hypothesis: We assessed the hypothesis that the interaction of a stent retriever device with a clot in proximal cerebral arteries typically leads to an encasement of the clot after a steady state of clot-device interaction is reached.
Methods: We studied how two different stent retrievers (the Trevo and Aperio device) interact with clots made from human blood with a Chandler loop. Therefore, we injected 30 preformed clots of constant length but variable thickness into tapering models of the distal internal carotid artery, the main stem and M2 segments of the middle cerebral artery and filled the remaining lumina with x-ray contrast agent. We then performed stent retrieving procedures with high resolution biplane angiographical imaging to capture all phases of the retrieving procedure without aspiration. We measured penetration depth of the stent struts into the clots, occurrences of clot rupture and the time intervals until a steady state of penetration was achieved.
Results: For both stents, we measured stent penetration depth in 60 evenly spaced positions for luminal diameters between 4.2mm and 1.3mm. Above a clot thickness of 2.3mm (Aperio) and 2.1mm (Trevo), a steady state penetration width of 0.5 mm (SD: 0.3 mm) for Trevo and 0.8 mm (SD: 0.4 mm) for Aperio was observed after 2.2s (Trevo) and 5.8 seconds (Aperio) and no encasement was observed. Below a clot thickness of 2 mm, clots were completely encased in 41% (Trevo) and 58% (Aperio), although in both both stents more than 80 % were disrupted. The steady state of penetration was achieved after 3.5s (Trevo, SD: 1.8 s) and 4.8 s (Aperio, SD: 2.1 s).
Conclusions: Instead of being encased, thick clots are eccentrically attached to the outer surface of stent retrievers within a few seconds until steady state is reached. This results in the risk of stripping off the clots at the entrance of an aspiration catheter. Encasement of clots is only observed in thin clots at the price of clot disruption with a steady state after a few seconds. Both aspects imply that stent-retriever procedures can only be effective with additional close distance aspiration.
Author Disclosures: S. Lamprecht: None. O. Jansen: None. C.H. Riedel: None.
- © 2015 by American Heart Association, Inc.