Comparative in vitro study of five mechanical embolectomy systems: effectiveness of clot removal and risk of distal embolization

Abstract

We report an in vitro study comparing the effectiveness of clot removal and clot fragmentation of five embolectomy systems. A flow model was embolized with fresh and old thrombi, occluding an inner diameter of 2-5 mm simulating internal carotid artery (ICA), basilar artery (BA) and middle cerebral artery (MCA) branch occlusion. Embolectomy was performed using five retrieval systems: CATCH (Balt), Merci retriever (Concentric), InTime and Attracter (Boston Scientific), and the Phenox Clot Retriever (Phenox). Clot removal and evidence and type of thrombus fragmentation and distal embolization were recorded. There were no observable differences attributable to thrombus age. The Merci, CATCH and Phenox Clot Retriever were equally able to mobilize and remove thrombi with the exception of one particularly firm clot. There were marked differences in terms of thrombus fragmentation and distal embolization. All devices produced micro- and macrofragments during penetration and retrieval. The Phenox Clot Retriever was able to filter fragments. The InTime and Attracter devices failed to retrieve thrombi in this model and achieved partial removal at best with a tendency towards thrombus displacement and fragmentation. Within limits, the experimental setup was appropriate for generating occlusions of diameter 2-5 mm of various lengths, simulating ICA, BA and MCA thromboembolism. In this model, thrombus mobilization appeared to be less dependent upon the individual design of the retrieval system than on thrombus fragmentation. The ability to prevent distal embolization is, however, strongly dependent on the ability of a thrombectomy device to capture fragments that are generated during removal of the device.