24 Balloon-Assisted Coiling
General Description
Balloon-assisted techniques for aneurysm coiling are essential for endovascular neurosurgeons. Balloon-assisted coiling is mainly used for aneurysm neck remodeling and side branch protection. A balloon also stabilizes the coiling microcatheter within the aneurysm by preventing “kickback” of the microcatheter and obtaining more dense packing of the coils. For wide-necked aneurysms, balloon-assisted coiling can prevent the need for a stent; this can be very helpful in the case of a subarachnoid hemorrhage from ruptured aneurysms. Also, a balloon can be used as a safety net in case of intraoperative aneurysm rupture. A double-lumen balloon catheter allows for coil embolization and neck reconstruction by a single microcatheter.
Indications
Balloon-assisted coiling is indicated for the endovascular management of ruptured or unruptured narrow or wide-necked aneurysms. Some neurosurgeons always have a balloon handy in the event of aneurysm rupture.
Neuroendovascular Anatomy
Wide-necked aneurysms can be located anywhere in the intracranial circulation, including the paraophthalmic region, middle cerebral artery, anterior communicating artery, vertebral artery (VA), and basilar artery. The anatomy of each aneurysm should be analyzed on a case-by-case basis. Then the interventionist can decide whether balloon-assisted coiling is the best option. Aneurysms located at the basilar apex or the bifurcation of the internal carotid artery (ICA), middle cerebral artery, or anterior communicating artery can have a wide neck or project predominantly toward one arterial branch, and the need for balloon-assisted coiling might be necessary.
Perioperative Medication
Balloon-assisted coiling is usually performed under systemic heparinization. There is no need for antiplatelet therapy.
Intracranial Balloons
Balloons are classified as compliant and noncompliant. Compliant balloons are inflated slowly by hand and conform to the contours of the aneurysm neck and parent vessels and branches. Noncompliant balloons are not used for balloon-assisted coiling.
Compliant balloons that have a single lumen include the HyperGlide (Medtronic), HyperForm (Medtronic), Transform (Stryker), and Transform Super Compliant (Stryker). The diameters of these balloons range from 3 to 7 mm. The lengths range from 10 to 30 mm. The HyperForm and the Transform Super Compliant are highly conformable. This feature of adapting to the arterial anatomy allows these balloons to partially herniate into the aneurysm, which is very useful when the parent artery is in close proximity to or involved with the neck of the aneurysm.
Compliant balloons that have a double coaxial lumen include the Scepter (MicroVention) and Ascent (Codman). Scepter balloons have a 4 mm diameter and are 10–20 mm in length with a tip length of 5 mm. Ascent balloons have a 4 mm or 6 mm diameter and are 7–15 mm in length with a tip length of 3 mm.
Specific Technique and Key Steps
Endovascular access is obtained via a femoral arteriotomy with a micropuncture set. Under fluoroscopic visualization, a microwire is advanced through a transitional 6 French (F) dilator to the desired location in relation to the femoral head.
A 6–8 F guide sheath with a copilot valve is placed in the ICA or VA, depending on the aneurysm’s location. This can be done using a sliding catheter (e.g., Vitek catheter, Cook) or via an exchange wire, such as a 0.035-inch exchange length Glidewire (Terumo). Roadmapping technique is used for this process.
Initial digital subtraction angiography (DSA) runs of anteroposterior and lateral views are performed. Oblique magnified working views are obtained from a rotational 3D reconstruction of the DSA runs ( Fig. 24.1–24.3, Video 24.1–24.3 ).
If the aneurysm is distal or located in tortuous anatomy, a triaxial catheter system consisting of a guide catheter, an intermediate catheter, and a microcatheter is utilized for access to the aneurysm; otherwise, a biaxial catheter access system consisting of a guide catheter and a microcatheter will suffice.
If a triaxial system is utilized, the intermediate catheter must be large enough to hold both the coiling microcatheter and the balloon microcatheter. In the case of a basilar apex aneurysm, one microcatheter can be navigated through one VA, and the balloon can be navigated through the contralateral VA.
Before introducing the balloon into the patient, the balloon is prepared on the back table according to lumen type (double or single). Following its introduction, a single-lumen balloon requires a microwire in place at all times, because if that microwire is removed, air or blood will fill the balloon and it will no longer be visible. Balloon size is based on parent vessel size. Typically, a compliant balloon is utilized for coiling because it conforms to the ostia of the parent vessel and protects the neck of the aneurysm ( Video 24.1–24.3 ).
Typically, the balloon is placed through a separate rotating hemostatic valve on the guide sheath; however, the copilot valve of the guide sheath can also be utilized. Under roadmap working views, the balloon is navigated just distal to the aneurysm. A test inflation can be performed with a 1-mL or 3-mL syringe filled with contrast material to see whether the balloon is visible and how the contrast material travels once the balloon inflated.
After the balloon has been tested, it is deflated. The coiling microcatheter (e.g., SL-10, Stryker Neurovascular; DUO, MicroVention) is carefully navigated over the microwire into the aneurysm of choice ( Video 24.1–24.3 ).
The aneurysm volume is calculated using the measured width, length, and height, and the appropriate coils are selected. A framing coil is often inserted first, followed by filling coils.
HyperForm balloons are elliptical and more compliant than HyperGlyde balloons, which are ideal for cases in which asymmetric inflation is needed. HyperGlide balloons are oblong and elongated. As mentioned previously, these balloons allow some aneurysm herniation and are ideal for sidewall aneurysms such as ICA aneurysms.
A more natural coil deployment is possible with the balloon deflated. Coil material that is prolapsing is resheathed, and the balloon is inflated over the neck of the aneurysm, thus jailing the catheter within.
Once the coiling microcatheter is inside the aneurysm and the balloon is inflated, the coils are carefully placed under continuous roadmap working views. If the balloon is occlusive, it will need to be deflated intermittently to restore flow. The aneurysm should be coiled until no contrast material is visible within the interstices of the coil mass (i.e., 30%–40% packing density).
Once finished deploying coils, the balloon is slowly deflated and withdrawn under fluoroscopy monitoring to note coil stability. If stable, the balloon is reinflated, the coiling catheter removed, and the balloon is deflated and removed.
Final runs are then obtained in anteroposterior and lateral views.
Device Selection
In our practice, the following are common set-ups and devices used during balloon-assisted coiling.
21-gauge micropuncture set, Cope Mandril wire (Cook Medical), 6F dilator, 6–8F sheath.
Neuron or Neuron MAX 90 cm guide catheter (Penumbra) or Envoy XB DA guide catheter (Johnson & Johnson).
Vitek or 125-cm 5F Vertebral catheter (Cook) or 280-cm Glide exchange wire.
0.035-inch Glidewire.
Intermediate catheter, such as Sofia (MicroVention), Navien (Medtronic), or Catalyst (Stryker).
SL-10 microcatheter (straight, J, 45° or 90° varieties) or DUO microcatheter.
Standard or soft wire Synchro 2 (Stryker).
Continuous heparinized saline.
Platinum coils (hydrogel coils can also be used) (i.e., Cosmos framing coil and hypersoft fillers, MicroVention).
Single-lumen HyperForm or HyperGlide balloon or double-lumen Scepter XC balloon.
Pearls
An invisible balloon is a dangerous balloon. Always test a balloon on the back table to make sure it is intact (inflates and deflates properly; no leaks) and that no air is within. Once a single-lumen balloon is introduced, do not remove the microwire from it.
If a perforation is present while coiling, the balloon can be inflated immediately for hemostasis.
If by accident, the microcatheter perforates the aneurysm, begin coiling extravascularly outside the aneurysm and continue delivering the coil inside the aneurysm with the balloon inflated.
Always use micromovements when catheterizing an aneurysm.
Position the catheter two-thirds of the way into the aneurysm and be mindful of tension in the access system.
A balloon can rupture a vessel if it is too large for that vessel.
If the intervention is performed with the patient awake, be considerate of the fact that an overinflated balloon can be painful and some patients will not tolerate it for long periods of time.
At times, after coiling is performed and the balloon is deflated, a loop or tail of a coil can prolapse into the parent vessel. Aspirin prophylaxis will be needed to prevent emboli formation.
The balloon and microcatheter can push against one another, especially in small vessels. This increases the risk of emboli formation. Glycoprotein IIb/IIIa inhibitors can be utilized to treat emboli formation.
Always be mindful of extravasation.
Coils that are too large should be resheathed. It is dangerous to try to pack excess coils into the aneurysm.
If a long tail of a coil or a mass of coils prolapses despite balloon use, a stent may be necessary. If coils prolapse and embolize, they should be retrieved with a snare.
Hydrogel coils will swell. No. 10 coils are smaller than No. 18 coils and will have a lower packing density per coil.
Transcirculation approaches can be utilized for balloon placement by way of a separate groin puncture.
If catheter kickback is encountered during coiling, the inflated balloon can be minimally deflated, and the coil can be guided back into the aneurysm. The balloon can then be utilized to secure the catheter again.
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