4:10 PM Abstract No. 388 Ethylene vinyl alcohol copolymer (Onyx) for treatment of large venous vascular malformations: long-term results

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To describe the long-term results and advantages of ethylene vinyl alcohol polymer for treatment of venous vascular malformations. Since 2005, we have used Ethylene vinyl alcohol copolymer (Onyx 18 & 34) in the treatment of 62 patients with large, low-flow venous vascular malformations. There were 34 females and 28 males with ages ranging from 7–59 years (mean 25 years). Fifty-one of the malformations involved the extremities and 11 involved the chest, abdominal wall or pelvis. All patients were evaluated with MRI/MRA pretreatment. Onyx was delivered by direct injection with ultrasound and fluoroscopic guidance under tourniquet control. In a few cases Onyx was also delivered via a transarterial micro catheter positioned in large feeding vessels. Sodium tetradecyl (3%) foam was used also in conjunction with Onyx in six patients where there were associated smaller foci of malformation. Histologic examination of tissues from patients whose embolized lesions were subsequently explanted was performed. Ethylene vinyl alcohol copolymer (Onyx) was found to be useful for occlusion of large venous channels in venous malformations. Unlike sclerosing agents, its visibility allowed direct observation of filling of the venous malformation during injection. When used alone, there was minimal post procedure discomfort. There were two complications: one extrusion of Onyx from a lesion on the sole of the foot, which healed without sequelae and one instance of embolization of a small Onyx fragment to the lung, also without sequelae. On H & E stains, the Onyx was noted to be distributed in the intraluminal spaces with associated mild foreign body type giant cell reaction. Permanency of the copolymer was demonstrated on long-term imaging follow-up. Ethylene vinyl alcohol copolymer (Onyx) is a safe, durable agent for treatment of venous vascular malformations. It is of particular value in malformations with large venous channels. Unlike standard sclerosing agents, Onyx behaves as a filler, and is not dependent upon generation of an inflammatory reaction for occlusion. Its opacity allows visualization of filled channels. It can be used alone or in conjunction with sclerosing agents.