Long-term Magnetic Resonance Angiography Follow-up for Recanalized Vessels after Mechanical Thrombectomy

Background: Mechanical thrombectomy is an effective revascularization therapy for acute intracranial large vessel occlusion. We retrospectively evaluated magnetic resonance angiography (MRA) follow-up data to assess the long-term patency of recanalized vessels after mechanical thrombectomy. Methods: We retrospectively reviewed medical records of consecutive patients who had undergone mechanical thrombectomy for intravenous tissue plasminogen activator-failed/ineligible acute intracranial major vessel occlusion between October 2010 and April 2013 at our institution. MRA follow-up was performed at baseline and at 24 +/- 6 hours and 3 months after mechanical thrombectomy. Results: Forty-nine patients underwent mechanical thrombectomy for acute intracranial major vessel occlusion. Mean age was 69.7 +/- 11.5 years, and baseline median National Institute of Health Stroke Scale score was 15 (range, 8-24). Occlusion was found in the internal carotid artery in 18 patients (36.7%), middle cerebral artery in 26 patients (53%), and vertebral-basilar arteries in 5 patients (10.2%). Successful recanalization, as defined by a thrombolysis in cerebral infarction flow grade of 2b or 3, was achieved in 40 patients (81.6%). MRA follow-up at 24 hours after the treatment revealed that reocclusion of recanalized vessels was observed in 3 of 38 patients (7.9%). Long-term MRA follow-up showed that 2 of 27 patients (8.3%) developed diffuse severe stenosis of treated vessels. Both the patients had undergone treatment for middle cerebral artery occlusion with the Merci retriever and had been administered only anticoagulants, but not any antiplatelets. Conclusions: Reocclusion or late stenosis of successfully recanalized vessels was observed in 16.2% of patients. Long-term MRA follow-up of recanalized vessels will be useful, in particular, for the patient with middle cerebral artery occlusion who undergoes mechanical thrombectomy.