♦ Preoperative
Operative Planning
- According to the rationale that prompt treatment will limit the potential for rebleeding, all ruptured aneurysms should be treated as soon as practical after admission.
- The strategy of treatment is complete aneurysm isolation from the circulation
Imaging
- Computed tomography
- Degree of hydrocephalus and need for ventricular drain
- Heavy neck calcification may push toward coiling
- Aneurysm pointing into brain stem better for endovascular treatment
- Degree of hydrocephalus and need for ventricular drain
- Magnetic resonance imaging
- Look for partial thrombosis; may be at increased risk for recanalization if coiled
- Brain stem edema may be present because of mass effect and perforator infarction.
- Look for partial thrombosis; may be at increased risk for recanalization if coiled
- Angiography
- Diagnostic angiography should be performed with specific views that provide excellent visualization of all brachiocephalic vessels and the aneurysm neck and associated branches.
- Rotational angiography and three-dimensional image reconstruction is beneficial to fully define aneurysms, especially in the case of wide-necked or complex-shaped aneurysms.
- The overall aneurysm size, the neck size, and the dome-to-neck ratio of the aneurysm should be determined.
- A dome to neck ratio of ≤2:1 and giant, dissecting partially thrombosed or fusiform aneurysms may make coiling difficult.
- Special attention should be made to the location of the aneurysm in relationship to the posterior clinoid process on fluoroscopic images for surgical planning and clip versus coil decisions.
- The strategy of treatment is complete aneurysm isolation from the circulation using endovascular coils placed directly into the aneurysm, preserving flow in the parent artery and its branches, specifically posterior cerebral arteries and superior cerebral arteries for basilar tip aneurysms.
- In the case of giant or fusiform aneurysms, stent-assisted coiling or balloon occlusion testing followed by vertebral artery sacrifice should be considered, but not routinely in the case of subarachnoid hemorrhage patients. The vertebral sacrifice may be unilateral or staged bilateral depending on the circumstances. Rarely, basilar occlusion may be performed endovascularly
- Patients treated for nonemergent, unruptured basilar artery aneurysms with stent-assisted embolization should be treated with 75 mg of clopidogrel and 325 mg of aspirin for at least 5 days before endovascular procedure and maintained on the same dosage for at least 12 weeks with aspirin continued indefinitely.
- Diagnostic angiography should be performed with specific views that provide excellent visualization of all brachiocephalic vessels and the aneurysm neck and associated branches.
Special Equipment
- As for retrograde percutaneous femoral artery puncture
- Five to 7.5 French (F) sheath
- A 5F catheter and guide wire (for diagnostic angiogram)
- A 6 to 7F guiding catheter (7F required for side-by-side coiling and balloon remodeling microcatheters. Alternatively, this can be performed via guide catheters in each vertebral artery).
- Over-the-wire microcatheters
- 0.035-inch guide wire and micro–guide wires
- Microballoon catheter for balloon remodeling and/or stents as necessary
- Endovascular detachable coils
Anesthetic Issues
- In awake patients, the diagnostic portion of the procedure can be done under local anesthetic with conscious sedation.
- In unconscious or patients with impaired level of consciousness, general anesthesia is used for all portions of the procedure.
- General anesthesia is highly recommended for the coil procedure to allow for optimal imaging.
- Protamine should be readily available if intraoperative rupture occurs.
♦ Intraoperative
Positioning
- The patient is placed in the supine position.
- Intravenous antibiotics, if needed, are given.
- A Foley catheter is placed.
- The proper shielding is placed on the patient.
- Both inguinal areas are shaved and prepped with iodine solution.
- A sterile drape is placed over the prepped areas.
- The head is positioned in neutral position and gently taped in place.
Technique
- A four-vessel diagnostic angiogram is performed with all views necessary to determine aneurysm morphology and its association with the parent artery and its branches. The direction a basilar tip aneurysm points (anterior or posterior to the brain stem) is extremely important for clip versus coil decisions.
- Using a common femoral approach, the region over the right femoral head is examined under fluoroscopy to determine the appropriate entry site into that artery.
- The skin and subcuticular tissues over the artery is infiltrated with the appropriate local anesthetic: 1% lidocaine and 0.5% bupivacaine in a 50:50 mixture.
- The artery is entered with a 19-gauge single-wall needle, and upon the brisk return of bright arterial blood, a Benson wire is inserted through the needle and advanced into the abdominal and thoracic aortas under direct fluoroscopic guidance.
- A 5F sheath is placed over the guide wire; this is then sutured to the skin and perfused with heparinized saline throughout the entirety of the procedure.
- A 5F diagnostic catheter is then advanced over the abdominal and thoracic aortas under direct fluoroscopic guidance and is used to access the patient’s brachiocephalic vessels.
- Anteroposterior and lateral angiographic images of the head are obtained.
- A rotational angiographic image of the head is obtained of the parent artery of interest with a machine injection of contrast. Acquisition of these rotationally-acquired angiographic images is sent to the three-dimensional workstation, where reconstruction is performed.
- Following this angiogram, in preparation for the coiling procedure, the 5F intravascular sheath is exchanged for a 6.5F sheath over a guide wire that is then sutured to the skin. Bilateral groin punctures may be required if guide catheters to be placed in with vertebral arteries.
- The patient is heparinized during the coiling portion of the procedure, and this is maintained throughout the procedure (activated clotting time checked hourly and heparin adjusted accordingly to maintain a baseline of two to three times the baseline); some centers begin heparin at the start of the procedure and other centers wait until the first coil is placed.
- A variety of guidecathers, micro–guide wires, and microcatheters are used to access the aneurysm under direct fluoroscopic and digital roadmap guidance.
- The micro–guide wire is then removed, and detachable platinum coils are advanced through the microcatheter into the aneurysmal sac.
- The largest coil is used first to form the initial frame, and smaller coils are then used to occlude the aneurysm.
- Proximal and distal radio-opaque markers on the microcatheter are used to maintain the catheter position and angiography is used prior to each coil release to assess coil position stability and patency of the parent vessel. Evaluation is also made for any evidence of rupture as evidenced by contrast extravasation and physiologic response (i.e., increased pulse rate and blood pressure).
- The coil placement is continued to increase density until complete or near complete occlusion is achieved. This may require significant catheter manipulation and repositioning.
- It is critical to avoid displacement of the microcatheter into the thin aneurysm wall which may lead to immediate rupture.
- Proximal and distal radio-opaque markers on the microcatheter are used to maintain the catheter position and angiography is used prior to each coil release to assess coil position stability and patency of the parent vessel. Evaluation is also made for any evidence of rupture as evidenced by contrast extravasation and physiologic response (i.e., increased pulse rate and blood pressure).
Giant, Wide Neck, or Fusiform Posterior Communicating Artery Aneurysms
- In giant and wide neck aneurysms, occasionally an over-the-wire microballoon catheter is inserted through a larger guiding catheter to cover the aneurysm neck during coil deployment. The balloon is inflated during coil deployment and can be inflated and deflated prior to detachment to asses for coil stability.
- Giant, wide neck, or fusiform basilar artery aneurysms that are not suitable for clipping usually receive stent-assisted coil embolization, but may receive endovascular parent vessel sacrifice.
Stents and Embolization
- Patients that fail balloon occlusion or with aneurysm architecture that is amenable may be candidates for stenting-assisted coil embolization.
- Small aneurysms may rarely thrombose following stent deployment without coil embolization.
- A stent allows the insertion of embolic coils through the stent openings or through a catheter “trapped” into the aneurysm along the deployed stent as it may be difficult to pass the microcatheter through the stent interstices.
- Two aneurysm stents are currently approved by the U.S. Food and Drug Administration. The Neuroform stent (Boston Scientific, Natick, MA) comes in two varieties depending on the number of cross links in an open-cell design and comes in various lengths and diameters. It is deployed through a preloaded catheter that is placed across the aneurysm neck over an exchange length guide wire previously placed via a standard microcatheter. The Neuroform stent cannot be recaptured. The Enterprise stent (Cordis Endovascular, Irvine, CA) is a closed-cell design available in a single diameter and is deployed though a defined catheter that is placed distal to the aneurysm via a standard length guide wire. The stent can be recaptured and repositioned after up to 70% of its length has been deployed.
- Stent use in basilar tip aneurysms traditionally involves one stent; however, two stents may be used in a “Y” configuration (see following text). Single stent placement involves placing the stent across the aneurysm neck from the basilar artery to one of the posterior cerebral arteries (PCAs). The PCA choice is made based on the aneurysm morphology and the vessel most at risk for coil herniation.
- The Y configuration involves deployment of the traditional basilar-PCA stent. Following this, a second catheter is navigated through one of the openings in the first stent and a second stent is deployed into the other PCA through the first stent and inside the other stent within the basilar artery in a telescoping fashion. Coils can then be deployed into the aneurysm through these stents, or by a catheter “trapped” in the aneurysm prior to stent deployment.
- Approaches have also been used to access the contralateral PCA from a catheter placed up the internal carotid artery and through the posterior communicating artery to place a stent horizontally across the neck of basilar tip aneurysms, parallel to the P1 segments and perpendicular to the axis of the aneurysm.
Sheath Removal
- The sheath is removed.
- The arteriotomy is closed with a closure device after the patient is given intravenous antibiotics.
- Heparin is routinely continued at some centers for 24 to 48 hours, or is not continued and allowed to wear off naturally at others.
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