Very Late Thrombosis of Flow-Diverting Constructs after the Treatment of Large Fusiform Posterior Circulation Aneurysms

BACKGROUND AND PURPOSE: The PED is a new endoluminal construct designed to exclude aneurysms from the parent cerebrovasculature. We report the very late (>1 year) thrombosis of PED constructs in 2 patients. RESULTS: Two patients with very large fusiform basilar trunk aneurysms underwent parent artery reconstruction with the PED. Both patients were maintained on dual antiplatelet therapy throughout the first year following treatment. Follow-up conventional angiography, performed 12 months after treatment, demonstrated, in both patients, thrombosis of most of the aneurysm with minimal residual flow through the construct and into the aneurysm fundus. In response to the residual filling, clopidogrel was discontinued (aspirin therapy was maintained). Both patients presented with symptomatic acute occlusions of the PED constructs within 14 days of clopidogrel discontinuation. DISCUSSION: Patient 1 presented with constitutional symptoms that progressed to severe headache without other neurologic signs or symptoms. Occlusion of the PED construct was confirmed with conventional angiography. MR imaging demonstrated no evidence of infarction or parenchymal injury. The headaches were managed successfully with steroid therapy. Patient 2 presented with a syndrome of acute basilar occlusion with brain stem stroke. Complete occlusion was confirmed on angiography. Emergent thrombolysis with mechanical revascularization was performed successfully; however, the patient ultimately succumbed to the infarction. CONCLUSIONS: It appears that flow-diverting constructs built across large circumferential aneurysms may remain thrombogenic for much longer than conventional intracranial or peripheral bare metal stents. Constructs in these patients may remain susceptible to very late thrombosis, >1 year after implantation. These patients likely require long-term dual antiplatelet therapy (>1 year) to provide adequate prophylaxis against thrombosis. If these types of aneurysms demonstrate persistent residual filling months after PED reconstruction, operators should consider the placement of additional devices as an alternative to the discontinuation of 1 of the antiplatelet medications.