Background The mechanism by which a stent retriever removes intraluminal thrombus from an occluded vessel in humans has not previously been studied. This study performed contrast-enhanced high-resolution cone beam CT (CE-HRCBCT) during deployment of the stent retriever to observe the interaction between the strut and intraluminal thrombus intraoperatively. We also discuss the mechanism by which the thrombus is retrieved.

Methods In 11 patients, mechanical thrombectomy was performed with a Solitaire stent retriever. The presence or absence of flow restoration (FR) was evaluated immediately and at least 5 min after deployment. Stent retriever findings on CE-HRCBCT were divided into two groups: (1) complete expansion; and (2) incomplete expansion.

Results FR was observed in all 11 cases (100%) immediately after deployment of the Solitaire stent retriever. Complete expansion was observed in only one case and incomplete expansion was observed in 10 cases. The thrombus was observed mainly near to or outside the strut of the stent retriever by CE-HRCBCT. Loss of FR was seen in only one of the 11 cases. Regardless of this, successful recanalization was achieved with only the stent retriever in nine cases.

Conclusions CE-HRCBCT showed that the Solitaire stent retriever rarely expanded fully and the thrombus was mainly near to or outside the strut. It may not be necessary to wait a long time to allow the stent to expand fully into the thrombus because the main capture mechanism seems to be engagement of the clot between the crossings of the struts of the Solitaire.