Therapy methods — Arteriovenous malformation

Therapy of an arteriovenous malformation (AVM) is very demanding and requires both clinical and interventional experience. In the early stages of an arteriovenous malformation, conservative therapy measures can help to delay progression of the disease or its complications (e.g., compression therapy).

The aim of invasive therapy is to occlude all shunts, if possible, and consequently improve the clinical symptoms. A complete cure is possible in some cases and in the case of an arteriovenous fistula (AVF).

To eliminate an arteriovenous fistula as well as the shunts or the nidus of an arteriovenous malformation, endovascular therapy is normally the first choice. Relatively new techniques are available for this purpose with positive results regarding the long-term course of the disease. Depending on AVM localization and extension, these endovascular techniques can in some cases be combined with subsequent surgical resections (especially if there is a nidus with multiple fine fistulas). Primary resection of an arteriovenous malformation is usually not technically possible. The goal of endovascular treatment must always be selective and complete occlusion of the nidus while sparing the surrounding tissue. Endovascular occlusion of feeder arteries (e.g., with coils and plugs), proximal embolization or surgical ligation of feeder branches can often produce a temporary improvement, but this is later followed by worsening of symptoms due to the formation of new feeder arteries supplying the nidus and true proliferation of the lesion. A long-term therapy plan usually comprises several treatment sessions. Incomplete occlusion of the nidus leads to expansion of the arteriovenous malformation in the course of the disease and should therefore be avoided.

Percutaneous or endovascular embolization is still the therapy of choice. The nidus and the early drainage veins of the arteriovenous malformation are closed with permanent liquid embolic agents via a transarterial access and angiography. The liquid embolics are ethylene-vinyl alcohol copolymers, n-butyl cyanoacrylate (nBCA) or pure high-percentage ethanol.

The administration of these embolic agents requires a great deal of operator experience, since the arterial supply of the surrounding, unaffected tissue must be protected and displacement of embolic agents into healthy vessels must be avoided. If the angioarchitecture of the arteriovenous malformation permits, i.e., only a few drainage veins are present, embolization via a retrograde transvenous approach or a direct percutaneous approach is a very promising alternative. If it is technically and anatomically possible to completely occlude an arteriovenous malformation by embolization, a subsequent complete resection of the occluded nidus should be discussed. Additional resection of the occluded nidus may prevent recurrence in the long term. Additionally, resection may remove the remaining embolic material if it has a space-occupying effect.

In addition to the methods described here, pain therapy should always be considered and physiotherapy measures should be taken, especially if a muscle contracture is present.

As it is difficult to compare the success rates of the different forms of therapy, international experts recently developed a protocol to document the different success rates of a therapy in a comprehensive and standardized way. It is hoped that this will improve the comparability of the different techniques for the treatment of AVMs and subsequently make it possible to improve and further develop the therapy options.