Operative Planning

Special Equipment

• A 6 to 6.5 French (F) sheath
  
• A 6F guiding catheter
  
• Flow-directed or over-the-wire microcatheters
  
• Two-tip marker microcatheter
  
• 0.035-inch guide wire and micro–guide wires
  
• A 5F diagnostic catheter
  
• Exchange wire
  
• Particulate embolic materials: polyvinyl alcohol, Embosphere (BioSphere Medical, Rockland, MA), or Gelfoam particles, usually 50 to 1000 U, and iohexol
  
• N-butyl cyanoacrylate (NBCA)
  
• Absolute ethanol
  
• Platinum coils
  
• May consider Onyx as an alternative to cyanoacrylate

Anesthetic Issues

• Monitored anesthetic care can be used to allow provocative testing prior to embolization of a feeding vessel and is usually adequate for patient comfort and immobility.
  
• General anesthesia may be used for patients who are agitated/confused or who have airway compromise.
  
• Protamine should be readily available if an intraoperative rupture occurs.

Monitoring

• Provocative testing is performed with amobarbital and cardiac lidocaine injections of the feeding vessels through the microcatheter to determine that embolization will not result in a neurologic deficit.
  
• Somatosensory evoked potentials and motor evoked potentials may be indicated, particularly in the embolization of spinal arteriovenous malformations.

Positioning

Technique—Transarterial

• Perform femoral artery puncture and insert a 6 Fr sheath as described.
  
• Insert 6F guiding catheter through 6 Fr sheath.
  
• Keep patient well-heparinized throughout the procedure.
  
• Perform a six-vessel diagnostic angiogram (include external carotid and subclavian arteries and their branches when indicated).
  
• Determine which major vascular branches are contributing to the AVF and determine the draining patterns for each.
  
• Advance the guiding catheter to one of the major parent vessels (i.e., carotid or vertebral artery) and connect to a continuous flush system with heparinized saline.
  
• Obtain a roadmap of the parent vessel.
  
• Steam-shape the microcatheter to best fit the feeding artery-parent vessel complex.
  
• Navigate a microcatheter into the feeding artery of the AVF proximal to the fistula. This may require gentle manipulation of the microcatheter with normal saline flushes or with a microguide wire.
  
• The strategy for embolizing AVFs should include the obliteration of the fistulous site with flow of liquid embolic agent into the venous system, thus obliterating all fistulous components.
  
• Obtain a selective angiogram of this branch and evaluate the transit time (reflecting the speed of blood flow through this fistula).
  
• With the noted transit times in this feeding vessel, mix the NBCA with lipiodol (for opacification of the solution and to vary the setting time of the NBCA) and to the appropriate setting time (usually a mixture of 1 mL NBCA to 3 mL lipiodol allows for a safe controlled delivery of embolic agent in feeding vessels with “average” transit times).
  
• Flush the microcatheter with 10 to 15 mL 5% dextrose (ionic solutions will result in the polymerization of the NBCA within the mirocatheter).
  
• Under subtraction angiography, inject the NBCA slowly, using the full-column (1-mL syringe) flow-controlled technique. When the agent is seen to enter the draining vein, stop injection for 1 to 2 seconds and then resume. Stop the injection when reflux to the proximal microcatheter is noted.
  
• Aspirate the syringe and quickly withdraw the microcatheter from the guiding catheter and inspect the microcatheter for clots or fracture (total injection volume should be between 0.4 and 0.8 mL).
  
• Perform a control angiogram to confirm occlusion of the pedicle and preservation of all normal cortical venous drainage.
  
• Proceed with choosing a second feeding pedicle and proceed as above.
  
• In general, embolization should continue until at least there has been a resolution of cortical venous drainage or complete occlusion is noted.
  
• An alternative approach is the use of Onyx, which may allow for deeper penetration and more extensive occlusion of the fistula, given its unique properties.

Technique—Transvenous Embolization

Sheath Removal (Patient not Heparinized)

• Femoral arteriotomy occlusion device such as Perclose or VasoSeal should be used to achieve closure of the arteriotomy
  
• Mild femoral artery compression if oozing is noted

• Systolic blood pressure < 160, lower extremity immobility
  
• Monitor groin for hematoma and distal pulses
  
• Monitor for stroke symptoms
  
• Intravenous fluid hydration
  
• Patients are usually discharged on postoperative day 1