Thrombectomy of calcified emboli in stroke. Does histology of thrombi influence the effectiveness of thrombectomy?

Background and purpose Thrombus composition has been postulated to affect the success of endovascular therapy. Calcified clots are composed of large amounts of calcium phosphate which influences their mechanical properties and may serve as a model for testing this hypothesis. The aim of this study was to evaluate the recanalization and complication rates of calcified thromboemboli in patients with acute ischemic stroke who underwent thrombectomy. Material and methods A retrospective analysis was performed of all calcified intracranial thromboemboli in patients suffering an acute ischemic stroke, referred for endovascular therapy at two centers between January 2013 and July 2016. Results Eight patients with a calcified intracranial clot underwent stent retriever thrombectomy (five women; mean age 80 years). Mean clot attenuation was 305 HU (range 150-640 HU). Successful reperfusion defined, as Thrombolysis in Cerebral Infarction grade 2b-3 was achieved in only one patient (12.5%). Two periprocedural adverse events occurred: one peripheral vessel perforation which was coiled and one inadvertent stent retriever detachment due to fracture of the stent retriever wire. Conclusion Stent retriever thrombectomy of calcified thromboemboli seems less effective than with other types of clots. Different mechanical properties of calcified clots may render them stiffer and less accessible for stent retrievers. When faced with a calcified intracranial thromboembolus in clinical practice, a more contained approach may be warranted in view of low recanalization rates, and the potential for periprocedural adverse events.