Background and purpose Effectiveness of currently used mechanical thrombectomy devices has been evaluated using animal models mainly based upon the angiographical data analysis. However very little has been described about the histologic changes observed in the arteries treated with mechanical thrombectomy devices. The purpose of this study is to evaluate acute arterial histologic changes induced by mechanical thrombectomy using a dedicated swine stroke model.
Materials and Methods A total of eight Superficial Cervical Arteries in four swine were occluded with experimental thrombus and treated using the Merci Clot Retrieval System®. Each treated artery was harvested immediately after the procedure and histologic analysis of each arterial sample was performed. Four untreated Superficial Cervical Arteries were used as controls.
Results A total of 24 attempts at clot retrieval were made. The average number of retrieval attempts per artery was three. Circumferential intimal denudation and separation of smooth muscle layers in the tunica media were seen in all samples. The intimal denudation was seen regardless of the number of retrieval attempts. A minor sub-intimal dissection was seen in one artery. Arterial perforation with sub-adventitial hematoma was seen in two arteries and these findings were associated with microwire/microcatheter navigation rather than the use of the clot retrieval device.
Conclusion Minor histologic changes including intimal denudation and separation of smooth muscle layers in tunica media were seen in every artery treated by mechanical thrombectomy. Two arteries that showed major histologic change (sub-adventitial hematoma) were both associated with microwire/catheter navigation rather than the use of the clot retrieval device. It is possible that major arterial injury (eg vessel perforation) during the mechanical thrombectomy is more likely to be associated with microcatheter/microwire navigation rather than clot retrieval itself. This animal model may be useful in the preclinical safety evaluation of the mechanical thrombectomy devices.