Transvenous Approach for the Treatment of Cerebral Arteriovenous Malformations

• Failure to safely and effectively position the embolization microcatheter.[ Time Frame: within day of procedure ]
  Failure to reach a safe and effective microcatheter position for embolization.
• Any procedural complication leading to transient new neurological deficit.[ Time Frame: <5 days ]
  Any procedural complication leading to transient new neurological deficit.
• Any procedural complication leading to new neurological deficit.[ Time Frame: ≥5 days ]
  Any procedural complication leading to new neurological deficit.
• Any treatment-related complication that prolongs hospitalization by ≥5 days.[ Time Frame: Within one week ]
  Any treatment-related complication that prolongs hospitalization by ≥5 days.
• Incidence of new ischemia following treatment (Brain MR imaging prior to discharge with diffusion sequences).[ Time Frame: within 5 days post procedure ]
  Incidence of new ischemia following treatment (Brain MR imaging prior to discharge with diffusion sequences).
• Length of hospitalization (days).[ Time Frame: ≥5 days ]
  Length of hospitalization (days).
• Patient discharge to a location that is not his/her home.[ Time Frame: through to 3 (+/- 1) months follow-up ]
  Discharge to location other than home.
• mRS at discharge and 3(+/-1) months.[ Time Frame: through to 3 (+/- 1) months follow-up ]
  mRS at discharge and 3(+/-1) months.
• Incidence of new admission to hospital during follow-up.[ Time Frame: Within 3 +/- months post final treatment ]
  Incidence of new admission to hospital during follow-up.
• Incidence of intracranial hemorrhage during follow-up.[ Time Frame: Within 3 +/- months post final treatment ]
  Incidence of intracranial hemorrhage during follow-up.
• Incidence of residual AVM on confirmatory catheter angiography at 3(+/-1) months post-treatment.[ Time Frame: at 3(+/-1) months post-treatment. ]
  Incidence of residual AVM on confirmatory catheter angiography at 3(+/-1) months post-treatment.

A new endovascular route for the treatment of brain AVMs may be possible in some cases: Trans-Venous Embolization (TVE). The technique uses microcatheters to navigate to the draining veins of AVM, to reach and then fill the AVM nidus retrogradely with liquid embolic agents until the lesion is occluded. This technique has the potential to improve on some of the problems with the arterial approach to AVM embolization, such as a low overall occlusion rate. However, by occluding the vein first, and filling the lesion with the embolic agent in a retrograde fashion, the method transgresses a widely held dogma in the surgical or endovascular treatment of AVMs: to preserve the draining vein until all afferent vessels have been occluded. Nevertheless, the initial case series have shown promising results, with high occlusion rates, and few technical complications. The method is increasingly used in an increasing number of centers, but there is currently no research protocol to guide the use of this promising but still experimental treatment in a prudent fashion. Care trials can be designed to offer such an experimental treatment, taking into account the best medical interests of patients, in the presence of rapidly evolving indications and techniques.

• Procedure: Standard Trans-Arterial Embolization (TAE)
  The standard TAE, without TVE, is used in patient allocated standard treatment. The arterial approach will consist of at least one attempted catheterization for trans-arterial injection of liquid embolic. If the operator deems, on the table, for a trans-arterial injection to be too dangerous, no arterial injection is necessary. Treatment, where indicated, can be completed through other means.
• Procedure: Trans-Venous Embolization (TVE)
  The experimental treatment is an attempt to completely occlude the AVM using venous catheterization and retrograde EVOH injection during the final session. The trans-venous strategy will consist of at least one transvenous injection of ethyl vinyl alcohol (EVOH), with the choice of delivery microcatheters and other technical details left to the individual operator's discretion.

• Active Comparator: standard Trans-Arterial Embolization (TAE)
  The standard TAE, without TVE, is used in patient allocated standard treatment. The arterial approach will consist of at least one attempted catheterization for trans-arterial injection of liquid embolic. Patients incompletely treated at the time of the final embolization procedure are adjudicated a failure to reach the primary outcome and can be treated using alternative standard options (including surgery, radiation therapy, conservative management). In addition, patients of the control group can also be offered TVE, if still feasible, once the TAE has been adjudicated to be a failure. If the operator deems, on the table, for a trans-arterial injection to be too dangerous, no arterial injection is necessary. Treatment, where indicated, can be completed through other means.
• Experimental: Trans-Venous Embolization (TVE) (+/- Arterial) strategy
  The experimental treatment is an attempt to completely occlude the AVM using venous catheterization and retrograde EVOH injection during the final session. TAE can be performed to prepare for final TVE during the same or one previous preparatory session, or TAE can be used to rescue an incomplete TVE. In some patients, balloon catheterization is used trans-arterially to assist TVE. It will be permissible to perform more than one treatment session when deemed necessary (occasionally to treat an AVM through the trans-venous route requires a two-stage approach, with a single trans-arterial attempt to decrease AVM filling prior to the definitive trans-venous approach, and this will be permitted). The trans-venous strategy will consist of at least one transvenous injection of ethyl vinyl alcohol (EVOH), with the choice of delivery microcatheters and other technical details left to the individual operator's discretion).