Posterior Communicating Aneurysm
Shape the tip of the microwire to a ‘C’ shape by giving a bend to the wire at the tip and then another bend further proximally.
Some Current Choices of Coils and Indications
- 1.
Bare Platinum Coils, e.g., GDC®
The most commonly used coil type.
Available as standard, soft, and ultra-soft. The firmness or rigidity in these types is dependent upon the amount of platinum used in the coil, i.e., the lesser the platinum, softer the coil.
Effective and perhaps most straight forward to deploy.
The size and length of coil chosen for deployment depends upon the size of aneurysm.
A thicker (0.018″, 0.038 cm) and firmer coil such as standard GDC 18 is best deployed in a large, unruptured aneurysm.
GDC 10 (0.010″, 0.025″ cm thick) is more commonly used.
Table 12.1 indicates various coil diameters and examples of microcatheters to be used based on these.
Table 12.1
Various coil sizes and examples of microcatheters to be used with each
Coil/guidewire diameter/thickness (inches)
microcatheter
0.010–0.012
Excelsior SL-10®; Prowler 10®
0.014
Prowler 14®
0.018
Excelsior 1018®; Prowler Plus®
The framing coil should preferably be ‘standard’ and the size large enough to cover the circumference of the aneurysm.
Soft and ultra-soft coils are usually deployed later on during the coiling or as ‘finishing’ coils, when standard coils become more difficult to deploy in aneurysm or do not stay within confines of the aneurysm.
The size and length of the coil selected progressively decreases as coil embolization progresses. Usually, the framing coil is the largest and longest coil.
Recently, Target® (Stryker Neurovascular, Fremont, CA) coils have been introduced as an alternative/replacement for GDC. Target coils are considered to cause less ‘microcatheter’ kickback toward the end of coiling.
- 2.
Hydrocoil® Embolic System
Hydrocoils® are coated with hydophilic gel that expands upon contact with blood. The principle is that the gel takes up and obliterates the inevitable space between coils.
The hydrocoil should initially be advanced into a bowl of warm Ringer’s lactate to soften it. Once the coil is noted to curl up more readily, it is retracted back into its sheath, then advanced through the microcatheter, and deployed within the aneurysm.
Deployment should not take long (e.g., more than 5 min), as the coil may expand within the microcatheter requiring removal of the occluded catheter.
Extra care is taken to keep the microcatheter free of blood, to prevent premature expansion of coils within the microcatheter. To this end, a two-way stopcock is placed between the RHV and microcatheter hub. The two-way stopcock is ‘closed’ to microcatheter when the RHV is opened to introduce the coil and it is then ‘opened’ to advance the coil into the microcatheter, after tightening the microcatheter RHV to the extent that the coil can be advanced with ease, but blood will not reflux back into the catheter.
The microcatheter is kept free of blood at all times.
Perhaps the best aneurysm obliteration results are achieved with hydrocoils.
Hydrocoils are associated with headaches in some patients. Theses headaches may respond to a short course of steroids.
- 3.
Matrix® Coils
These coils are coated with a copolymer, which upon hydrolysis induces inflammatory response.
Of the three coil types, these are most associated with aneurysm residuals and recurrence. We no longer use them.
Coil Embolization
Indications and Case Selection
Posterior circulation aneurysms, which include those of posterior communicating artery (per ISUIA data).
For coiling, the aneurysm should usually be larger than 5 mm.
Anterior circulation aneurysms in a WFNS grade III or IV patient, if technically amenable to endovascular intervention.
Anterior circulation aneurysms that are anatomically challenging from an open surgical approach.
Patient preference in anterior circulation aneurysms.
Recurrent aneurysm when previously coiled.
Incompletely clipped aneurysm (not always feasible for coiling).
A wide-necked aneurysm may be made amenable to coiling by stent placement across the neck, or using a balloon catheter.
Preoperative Management
ASA 325 mg on morning of procedure (in elective unruptured aneurysms).
Verify laboratory values including platelet count, BUN, CR, APTT, PT/INR, and ß-HCG (in pre-menopausal females).
Liquids only on morning of procedure.
NPO (for ≈6 h) when the procedure is to be performed under general anesthesia.
Continue prescribed medications (including ASA and anti-hypertensives).
Insert 2 IV lines.
Equipment
Rotating hemostatic valves (two).
Fluid delivery system (for sheath, catheter, and microcatheter).
Pressure tubing 12″ (for connection between injector and diagnostic/guide catheter).
Low pressure tubing (3, i.e., for sheath, guide catheter, and microcatheter).
Injector syringe 150 ml.
Syringes (20 ml; 3; 10 ml; 3).
Fluoroscope band bag.
Transducer 30 ml/min (for each heparinized saline flush system; usually 3, i.e., for sheath, diagnostic/guide catheter and microcatheter).
1% lidocaine + syringe with 18G and 22G needles (for local anesthesia).
Single-wall needle 18G or micropuncture kit.
Sheath, e.g., Terumo 6 Fr 10 cm.
2-0 Silk suture.
Diagnostic catheter, e.g., Terumo® 5-Fr angled catheter.
Guidewire, e.g., Terumo® angled glidewire 0.035 150 cm.
Codman 6 Fr Envoy® MPC 90 cm (or alternatively, 6-Fr Neuron Select™ catheter (Penumbra) with 5-Fr H1 Neuron catheter (Penumbra).
Microguidewire Transcend Ex 182 cm or Synchro2 200 cm.
microcatheter Excelsior® (1010, 1016 or 1018, depending on size of aneurysm and the coils intended to be used).
Coil Detacher.
Coils, e.g., GDC® (Stryker Neurovascular, Fremont, CA), Microplex® (Microvention, Tustin, CA), Hydrocoil® (Microvention), Target® (Stryker Neurovascular), Barricade™ (Blockade Medical, Irvine, CA).
Angioseal closure device (St Judes Medical, St Paul, MN).
Neuropack.
Technique
Gain access to femoral artery using modified Seldinger technique.
Insert 6-Fr short sheath over J-wire.
The sheath is connected to a continuously running flush of heparinized saline.
Ensure all flush systems are free of air bubbles and other foreign bodies.
Secure the sheath to the patient’s skin using 2-0 silk suture.
If the location of the aneurysm is already known or the patient’s vasculature is anticipated not to be tortuous, consider proceeding with the guide catheter straight away. Otherwise, a 5-Fr angled catheter is attached to a continuously running flush of heparinized saline that is free of any air.
Advance a 0.035 angled glidewire into the diagnostic catheter.
Insert the catheter through the sheath.
With the guidewire leading, catheterize the vessels and complete the diagnostic imaging, if not already done (see Chap. 11 Intracranial Angioplasty and Stenting for details).
Retract and remove the diagnostic catheter.
Attach a 6-Fr envoy guide catheter to the flush system that was previously used by the diagnostic catheter and make sure that there are no air bubbles or foreign bodies in the system.
Insert the 0.035 angled glidewire into the guide catheter.
Insert the envoy through the sheath and advance over wire to the vessel of interest, e.g., right ICA for right ophthalmic aneurysm or vertebral artery for basilar tip aneurysm.
For guide catheter placement, in general select the vessel that will provide the most direct access to the aneurysm.
Perform 3D angiography and select working views.
As shown in Fig. 12.1, measure the aneurysm including the widest circumferential diameter (a) of the aneurysm sac, longitudinal measurement from apex to base of aneurysm (b), and the width of the neck of aneurysm (c).
Fig. 12.1
Measurements to be performed during aneurysm coiling include the widest circumferential diameter (a) of the aneurysm sac, longitudinal measurement from apex to base of aneurysm (b) and the width of the neck of aneurysm (c)
If the aneurysm is multi-lobulated, then it should be measured as above, or each lobe treated and measured as a separate aneurysm.
The working views should enable good visualization of the neck of the aneurysm, as well as adjacent vessels to enable safe coil deployment.
Additionally, the view should also include the tip of the guide catheter, so that the surgeon remains cognizant of its location. If it is displaced downwards during the procedure, it may need to be re-advanced up to its original position to provide stability.
The microcatheter used for coiling has 2 radiopaque markers at its distal aspect. The distal marker at the tip of the catheter helps guide the tip through the vessels into the aneurysm. The proximal marker indicates when the coil has been completely placed in the aneurysm. When the marker on the pusher just crosses this proximal marker on the microcatheter (to form a ‘T’), the coil is ready for detachment. Any further pushing of the coil may cause the pusher itself to enter the aneurysm and rupture it.
These proximal and distal catheter markers must be visible at all times during positioning of the microcatheter in the aneurysm. If the distal marker becomes difficult to visualize due to the coils placed within the aneurysm, remain cognizant of the position of proximal marker at all times. Ensure that it does not inadvertently move further forward.
Attach the microcatheter to the flush system, e.g., Excelsior 1018 microcatheter if using 18 coils, with or without smaller coils. We most commonly use Excelsior SL 10 esp. for smaller aneurysms and ruptured larger aneurysms. If a concurrent lesion may require treatment, e.g., an AVM, with its feeding vessel bearing aneurysm/s, then a DMSO compatible microcatheter, e.g., Echelon-10 is used.
Insert a microguidewire into the microcatheter. We commonly use 0.014 or 0.010 Synchro2 or Transend Microguidewire.
Advance the microwire tip beyond the catheter tip.
Shape the tip of wire using the provided mandrel, and then withdraw the tip back into microcatheter. The shape of the microwire tip will depend upon the location of the aneurysm. The most commonly used tip shape is 45°. For access to anterior communicating aneurysms, a ‘shepherd’s crook’ shape is suitable. A ‘C’ shape is used for posterior communicating artery. Pre-shaped microwires are also available.
After shaping, retract the wire into the microcatheter.
Administer heparin 5000 IU IV, after the guide catheter has been positioned. In case of a ruptured aneurysm, we administer the heparin bolus only after the first coil has been successfully detached in the aneurysm.
Send an ACT approximately 15 min after administration of heparin, and repeat ACT hourly. Aim to maintain the ACT between 250 and 300 s throughout the procedure by administering additional heparin as needed.
Using fluoroscopy, advance the microcatheter and microguidewire through the guide catheter, until just short of the guide catheter tip.
Perform roadmapping through the envoy, while the microcatheter is proximal to guide catheter tip in the appropriate working views.
Navigate the microcatheter over the microwire preferably using two orthogonal views (Fig. 12.2).
Fig. 12.2
Roadmaps in two orthogonal planes for navigating into the anterior communicating aneurysm. The guide catheter is in the distal cervical ICA, just short of skull base. The microwire is appreciated in the microcatheter (arrow). The arrowhead points to carotid siphon. The importance of visualization in two planes is demonstrated. The carotid siphon (arrowhead) can be navigated well using the (a) view, but not (b) view. Both working views are oblique (note the projection angles in the upper left corner). Conversely for accessing the anterior communicating artery, the oblique view (b) is better. Therefore, for accessing the aneurysm, both planes need to be utilized
Advance the tip of microcatheter into aneurysm over the microwire.
Advance and retract the microwire through the catheter tip once or twice, to ensure that the catheter is stable and will not harpoon during coil deployment, nor will it displace when the coil is being advanced.
Then, remove the microwire completely.
Obtain roadmapping in the working view selected for coiling. It will show the aneurysm, its neck, and related vessel/s well. This working view may be the same as or different from the projection/s used for navigation to the aneurysm.
It is important to be able to definitively visualize that the coils are deposited within the aneurysm and are not compromising the adjacent vessels.
It is also important that all catheters remain stable during the procedure, e.g., if the guide catheter is displaced downward, re-advance it.
To do this, remove all slack from the system and tighten the RHV of the microcatheter. Loosen the RHV of the guide catheter, and visualizing under fluoroscopy, advance the guide catheter forward, while stabilizing the microcatheter and ensuring it does not move.
Coiling
Aneurysm coiling should preferably be performed with a biplane and usually working views in two planes are required to ensure safe coiling.
During the procedure, alternately visualize coil deposition in both planes to ensure coils remain within the aneurysm.
Select the first (framing) coil. We most frequently use GDC® coils.
The size of the framing coil should be consistent with the diameter of the aneurysm, e.g., if the aneurysm is 6 mm in diameter, select a standard bare platinum coil that has a primary loop diameter of 6 mm, or slightly larger. The length of the coil will also depend on the size of the aneurysm, e.g., for a large aneurysm use the longest coil that you anticipate can be placed within the aneurysm. Therefore, a ‘6X9’ GDC coil indicates that the loop formed by the coil is 6 mm in diameter, while the total length of the coil is 9 cm (i.e., first number [loop] is expressed in mm and the second [length] in cm).
Prepare coils as follows:
Remove the coil from containing plastic ring.
‘Unlock’ the sheath. This involves sliding off the black plastic piece on Hydrocoil® embolic system (Microvention, Inc., Tustin, CA) or twisting the proximal end of sheath in clockwise direction at the crimped site on GDC® or Matrix® coils (Stryker Neurovascular, Fremont, CA).
Advance the coil out into a bowl of warm lactated Ringer’s solution.
Withdraw the coil back into its sheath after soaking for 15–30 secs to soften it.
In case of Hydrocoils™, check that the detachment system is functional prior to coil insertion: the light will turn green on detachment mechanism, when proximal end of coil is inserted into detacher. DO NOT press detacher button during this test.
Using road mapping, advance the first coil as a framing coil. As indicated above, the dimensions of the primary loop of this coil should be close to aneurysm size. We usually use a coil equal to the diameter of the aneurysm, or slightly larger.
The coil is completely within the aneurysm once the marker on the coil pusher (that looks like a small line on the monitor) crosses the proximal marker (a dot) on microcatheter tip, forming a ‘T.’ The limbs of the ‘T’ should be perfectly abutted, such that there is no space between them (indicating the pusher in too far out). Nor should the vertical limb of the ‘T’ lie on either side of the dot on the catheter, indicating that the coil is not completely out of the microcatheter.
After the coil is completely deployed, perform angiography to ensure the coil is positioned adequately and is within the aneurysm.
If satisfied with coil deployment, detach the coil using the specific system provided for the purpose. It may be noted that detachment devices differ for different coil brands.
For GDC system, it comprises of a detachment box and two cables (black and red).
The detachment box is mounted on a pole preferably attached to the angio table. Or, it can be positioned on an independent pole, as long as care is taken, that this will not result in any problems, if the angio table is moved.
Ensure the box has a fresh battery that is working.
One end of each cable is plugged into the indicated slot on the detachment box. Maintain sterile precautions and ensure that the parts of the cables that will be on the operating field are not contaminated.
Attach a sterile 18–22G needle to the other end of the black (ground) cable and partially insert the needle into the patient’s thigh. Make sure that the femoral nerve and vessels are avoided.
Turn ‘on’ the detachment box.
The other end of the red coil is clipped onto the outer end of the coil pusher, once the coil has been deployed and is ready for detachment. Make sure that this attachment is performed right at the tip/end of the pusher.
Press the button on the box to initiate detachment. A beeping sound will indicate that the coil has detached from the pusher.
Turn ‘off’ the detachment box.
Step on fluoroscopy as the pusher is withdrawn from the catheter. Once it is confirmed that the pusher did indeed detach from the coil (demonstrated by the coil maintaining its position, as the pusher alone is seen to retract). After confirmation of actual detachment, the rest of the pusher can be withdrawn without using fluoroscopy. Rarely, the coil does not detach, in which case after confirming suitable positioning detachment is attempted again.
The first or ‘framing’ coil attempts to cover the entire circumference of the aneurysm (Fig. 12.3).
Fig. 12.3
A 5.6 × 7.5 mm anterior communicating aneurysm with a neck measuring 3.7 mm (same patient as shown in Fig. 12.2). A GDC 10 360° standard SR 5X9 mm framing coil has been placed that covers the entire aneurysm (arrow). Subsequent coils are deployed within the created ‘basket.’ Compare image to Fig. 12.2b
If the framing coil is well placed, further usage of road mapping for the following coils may not be required, as long as the coils are deposited within the confines of the framing coil (Fig. 12.3). Additionally, the frequency of angiography during deployment of additional coils may also be decreased. In short, live fluoroscopy alone may suffice, as long as the coil being deployed remains within the perimeter created by the framing coil.
Otherwise, periodically perform angiography to verify unimpeded flow through adjacent arteries. If there is doubt about whether the coil is within vessel lumen vs aneurysm, perform angiography with the axis of projection same as that of the blood vessel as if ‘looking down the barrel of a gun.’
Complete coiling is indicated by an angiogram demonstrating a lack of filling of the aneurysm or complete obliteration of aneurysm by coils (Fig. 12.4).
Do not attempt to place further coils into aneurysm beyond this point.
We have noted that the tip of the microcatheter is progressively pushed out of the aneurysm by the deposited coils. At this point, if the aneurysm is no longer filling with contrast, do not attempt to re-advance the microcatheter back into the aneurysm.
If there is residual filling, then attempt to replace the microcatheter into the aneurysm, using the microwire.
After completion of coiling, perform angiography in standard half Townes and lateral views (or same projections and magnification as baseline angiography), prior to the removing and discarding the microcatheter.
Ensure that there is no unanticipated finding such as a vessel occlusion or ‘cutoff’ by emboli, when compared to pre-coiling angiogram.
If embolic occlusion is present, use the microcatheter to administer Reopro or TPA.
If the angiogram is unremarkable, remove the microcatheter.
Retract the guide catheter into the femoral vessels.
Position the fluoroscopy tube at 33–45° ipsilaterally over the femoral region.
Perform angiography.
If arteriotomy is proximal to the femoral bifurcation and the vessel is ≥4 mm in caliber, perform angioseal closure.
Retrieving and Storing a Deployed Bare Platinum Coil
If a decision is made to remove a coil that has been partially or completely deployed (but not detached) in an aneurysm and it is anticipated that it may be required further on during the procedure, do the following:
Insert the proximal (outer) end of the pusher into the coil sheath. Note that one vacant coil sheath should always be stored on the operating table, anticipating this possibility. The crimped end of the sheath, in case of GDC coils, is cut off to make the maneuver of coil re-sheathing unhindered.
Continue to feed the coil pusher into the sheath while using fluoroscopy to ensure that the coil is exiting the aneurysm into the microcatheter as anticipated, at the other end. It also must be ensured that the exiting coil does not cause herniation of a previously detached coil, or any other untoward event.
Continue feeding the pusher into the sheath until its proximal end emerges from the proximal other end of the sheath. During this process, the operator must have direct access to some part of the pusher at all times.
Take hold of the emerged end of the pusher. Loosen the RHV to enable the insertion of the distal end of the sheath, which is closest to the RHV, halfway into it. Then, gently tighten the RHV around the sheath, ensuring that movement of pusher within the sheath is unimpeded.
Continue retracting the pusher and monitor fluoroscopically until the coil completely exits the aneurysm.
Watch the hub closely as the coil is pulled back.
Stop retracting, once the entire coil enters the sheath.
Loosen the RHV and recover the sheath. Re-tighten the RHV again.
Gently loop the sheath with the coil within and put it aside on the operating table.
After the next coil is deployed, store its sheath on the operating table to ensure a spare sheath is available at all times.
Note that this retrieval and storage cannot be performed for expanding coils, e.g., hydrocoils. If a decision is made to remove such a coil, it must be retrieved and discarded approximately within 5 min of initiating deployment. During retrieval, it may be discovered that the coil has expanded to the extent that it gets stuck within the microcatheter. In such a situation, DO NOT attempt to forcefully pull the pusher. The microcatheter will need to be removed along with the coil and then replaced by another.
Problems Encountered During Coiling and Solutions
Table 12.2 shows some possible problems/solutions.
Table 12.2
Problems/solutions during coiling
Problem
Solution
microcatheter kicks out of the aneurysm as the coil is being deployed
• Gradual retraction of the coil frequently causes the microcatheter tip to reenter the aneurysm. At this point, the following may be attempted
• Advance the coil more gradually into the aneurysm. A slower or faster deployment, or the coil loops depositing differently within the aneurysm, either of these may result in complete deposition of coil within the aneurysm
• Alternatively, advance the microcatheter slightly over the coil and then resume deploying the coil. Or
• Remove the coil entirely and replace with a shorter and/or softer coil
• If attempts to replace the microcatheter tip within the aneurysm do not succeed, then retract and remove the coil entirely. Advance the microwire through the microcatheter and then attempt to re-catheterize the aneurysm
• Conversely, if a majority of the aneurysm is coiled and re-catheterization is proving difficult, consider postponing completion of coiling to another day. With a small residual remaining, the patient is more protected against SAH compared to an untreated aneurysmRelated posts:
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