Histopathological Demonstration of Subacute Endothelialization Following Aneurysm Retreatment with the Pipeline Embolization Device.

Abstract

Endothelial cell coverage along the Pipeline embolization device (PED) is 1 of 2 primary proposed mechanisms of action of the device, along with induction of intra-aneurysmal thrombosis. The temporal course of endothelialization following device deployment is poorly understood in human patients. A 63-year-old female with a persistent aneurysm in the communicating segment of the internal carotid artery was treated with a second PED 14 months after the deployment of a first PED and subsequently developed a fatal intraparenchymal hemorrhage at 3 weeks postimplantation. Histopathological analysis at autopsy showed evidence of endothelialization along the second PED at this time, as well as neointimal growth between both devices. Patency of the vessel lumen with no intraluminal thrombus but thrombus showing early organization (endothelial cell ingrowth) was observed within the aneurysm dome. To our knowledge, this case represents the earliest demonstration of intimal cell growth along the PED. Aneurysm healing via endothelialization following flow diverter treatment may occur subacutely and not chronically as previously stipulated.