Delayed Complications Due to Polymer Coating Embolism after Endovascular Treatment

There have recently been reports of patients who developed postprocedural symptoms or alterations due to delayed foreign body embolisms observed in imaging findings. Polymer coating of devices have been described as a possible cause of foreign body embolisms, manifesting in delayed granulomatous responses and exhibiting characteristic imaging findings. In four of 4,025 patients who underwent coil embolization in our hospital or its affiliated facilities, similar findings were observed. Delayed lesions appeared between 1 month and 1 year after the procedures. There was extensive edema in the perfusion area of the treated vessels. In two cases examined by contrast-enhanced magnetic resonance imaging, multiple solid enhancing lesions within vasogenic edema were observed. Biopsy revealed a membranous foreign body in a blood vessel with surrounding foreign body granuloma formation in 1 case. Because these findings are similar to those of cases reported previously, they were considered as a foreign body embolism due to coating separations from the devices. Polymer coating separation occurs most frequently from guidewires. Especially if a metal introducer is used, the risk of separation increases. Surgeons should carefully follow the manufacturers' instructions when they use these devices and should acknowledge and report any events that may occur. Although these complications are extremely rare, further studies are warranted of similar cases; and we should prepare and share information on these intravascular devices for wide-scale dissemination in the industry.