Precautions for using a Filter Protection Device with a Flow Reversal Method during Carotid Artery Stenting: A Case Report on In-Filter Thrombus

The combination of a flow reversal with two balloons and a filter protection device is one of the safest methods that can be used during carotid artery stenting (CAS). Although major adverse events did not occur under restrict protection, we experienced a case of in-filter thrombus during the procedure. A 68-year-old male presented with temporary right hemiparesis. The radiological examinations revealed 95% stenosis on the origin of the left internal carotid artery (ICA). The patient underwent left CAS of wherein a proximal common carotid artery balloon, an external carotid artery balloon, and a distal ICA filter, with continuous flow reversal to the femoral vein, were used. Although the reversal circulation was established, a massive newly developing thrombus was found in the proximal side of the filter. After an additional systemic heparinization, the thrombus disappeared. The procedure was performed without any complications. Physicians should be aware of the risk of developing intraprocedural thrombosis in a filter protection device. Because the filter protection device is designed for the antegrade flow, it may promote the development of thrombus against the retrograde flow. Thus, the filter protection device should be retrieved first under the flow reversal circumstance to avoid the distal migration of a clot around the filter device.