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Abstract
Background Flow-diverting stents represent a substantial advancement in the treatment of cerebral aneurysms. They can, however, be associated with unique complications that may require management through adjunctive techniques.
Objective To present a technical report of a salvage technique used to realign a prolapsed Pipeline Embolization Device (PED) during the treatment of a giant internal carotid artery (ICA) aneurysm.
Methods A patient in his late 70s with an incidental giant supraclinoid ICA aneurysm presented for endovascular consideration. Treatment was planned using the PED. Following placement of the device there were two focal areas of incomplete expansion and balloon angioplasty was performed. This manipulation resulted in foreshortening of the distal aspect of the PED which caused the device to prolapse into the aneurysm. After multiple unsuccessful attempts to regain distal access, a salvage technique was attempted in which a balloon was inflated in the middle cerebral artery and, by applying traction, the PED was realigned with the parent artery.
Results After the PED was realigned, direct distal catheter access was achieved and a second Pipeline device was deployed, successfully covering the aneurysm neck with resultant flow stasis. The patient had no postoperative issues and was discharged 2 days later without deficit.
Conclusions The balloon-anchoring technique was successfully used to realign a PED that had prolapsed into a giant ICA aneurysm. This maneuver prevented potentially disastrous complications and allowed the satisfactory completion of the aneurysm embolization. This represents a useful salvage technique that should be considered when encountering a prolapsed stent.
- Balloon
- Aneurysm
- Flow Diverter
- Stent
- Technique
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Introduction
The development of flow-diverting stents is widely regarded as a significant advance in the endovascular treatment of cerebral aneurysms. While flow diverters may be quite useful for the treatment of aneurysms that were previously well-treated with classic endovascular methods, the most substantial difference with their implementation has been seen with large and giant aneurysms that were not well-treated with either endovascular or open cerebrovascular techniques. These aneurysms are often associated with tortuous arteries of the head and neck that make their treatment even more difficult.
The Pipeline Embolization Device (PED; ev3/Covidien Neurovascular, Irvine, California, USA) is currently the only FDA-approved flow diverter available in the USA. Despite the obvious utility and early reported success of this device, it is certainly not without potential complications and problems may arise during its use. Here we present a technical report of a salvage technique that was used to overcome a potentially disastrous problem during the deployment of a PED for the treatment of a giant cerebral aneurysm.
Methods
Patient presentation
A patient in his late 70s with a history of colon cancer was found to have a large internal carotid artery (ICA) aneurysm on a routine positron emission tomography scan. A subsequent CT angiogram revealed a 2.8×2 cm aneurysm arising from the supraclinoid segment of the left ICA (figure 1). Based on the patient's prognosis as well as the size and location of the aneurysm, endovascular treatment was scheduled. Given the appearance of the aneurysm and lack of other suitable options, the PED was felt to be the optimal treatment method. Due to the high likelihood of treatment with a PED, the patient was started on dual antiplatelet therapy with aspirin and clopidogrel 3 days prior to the procedure.
(A, B) Axial and sagittal CT angiogram images demonstrating the 2.8×2 cm left internal carotid artery aneurysm. Reproduced with permission from Barrow Neurological Institute.
Endovascular procedure
The patient was placed under general anesthesia and an 8 Fr sheath was inserted into the right common femoral artery. The patient was systemically heparinized and an angiogram was performed of the left ICA using a 5 Fr diagnostic catheter. The aortic arch was found to be tortuous and a bovine left common carotid artery was present. Angiography demonstrated a giant supraclinoid ICA aneurysm measuring 2.6 cm×2.5 cm×2 cm, with a neck of approximately 1.5 cm (figure 2). This was felt to be a suitable aneurysm for PED embolization. The 5 Fr diagnostic catheter was then exchanged for a 0.088 inch Neuron Max (Penumbra, Alameda, California, USA) guide catheter. Due to tortuosity of the cervical ICA, the guide catheter caused flow arrest when in a distal position and therefore the guide catheter was placed within the ICA approximately 3 cm from its origin.
(A, B) Posteroanterior and off-lateral angiographic images of the left internal carotid artery aneurysm. The off-lateral image clearly shows that the aneurysm arises distal to the ophthalmic artery. Reproduced with permission from Barrow Neurological Institute.
The decision was made to treat the aneurysm with a PED with subsequent coil embolization through a jailed microcatheter. An XT-27 microcatheter (Stryker Neurovascular, Kalamazoo, Michigan, USA) was advanced over a Synchro2 microwire (Stryker Neurovascular) across the aneurysm into the distal left middle cerebral artery (MCA). Due to the acute angle created between the parent vessel proximal and distal to the aneurysm, this required creating a substantial loop within the aneurysm in order to access the distal supraclinoid ICA. Once in the MCA, the microcatheter loop was easily withdrawn by pulling the wire back just proximal to the loop and gently retracting the catheter. A PX Slim microcatheter (Penumbra) was then advanced directly to the aneurysm dome. Once the microcatheters were in place, the PED was advanced through the XT-27 microcatheter. A 4.5×35 mm device was then deployed without difficulty, spanning from the distal supraclinoid ICA to the petrous ICA. The device diameter was chosen according to the diameter of the larger proximal parent artery, with the understanding that it would be slightly oversized in the distal ICA, hopefully resulting in stronger device purchase in the distal vessel. A long PED was used to ensure stability, given the tortuosity of the aneurysm and ICA; however, there was only a 1 cm distal landing zone proximal to the ICA terminus.
Following PED deployment, two focal areas of incomplete PED expansion were observed in the supraclinoid ICA and at the junction of the proximal ICA and the aneurysm (figure 3). In order to maintain the true lumen of the PED, the microcatheter was exchanged for a 4×20 mm Hyperglide balloon (ev3/Covidien Neurovascular) using an 0.010 inch exchange-length wire. Angioplasty was first performed across the most distal area of incomplete opening with resulting expansion of the PED. The balloon was then brought back to the proximal area of incomplete device expansion and angioplasty was performed. During inflation of the balloon and expansion of the proximal device, the distal aspect of the PED foreshortened. This caused the device to lose its purchase in the supraclinoid ICA and prolapse into the aneurysm. As the PED remained well opposed to the proximal ICA, flow was diverted directly towards the aneurysm dome. In addition, the distal end of the PED no longer coursed towards the supraclinoid ICA and instead pointed towards the middle of the aneurysm.
(A–F) Working angle angiographic images following placement of the initial Pipeline Embolization Device (PED). Unsubtracted images (C, D) taken immediately after PED placement show two focal areas of incomplete device expansion (white arrows). Following balloon angioplasty of these regions, the distal end of the PED (black arrows) prolapsed into the aneurysm (E, F). Reproduced with permission from Barrow Neurological Institute.
Attempts to regain access to the distal ICA and MCA through the PED were successful; however, this again required creating a substantial loop within the aneurysm. Despite the fact that we had previously been successful in straightening out the microcatheter within the aneurysm, multiple subsequent attempts to withdraw the loop of the microcatheter were unsuccessful, resulting in repeated loss of distal catheter position. This was felt to be largely due to resistance created by the distal end of the PED, which created a fixed and even more acute angle to the distal ICA, and directed the microcatheter into the aneurysm rather than allowing it to course directly to the supraclinoid ICA. Finally, after numerous unsuccessful maneuvers, the decision was made to attempt to straighten the existing PED using a balloon-anchoring technique. This required both a balloon and the delivery microcatheter, and therefore the microcatheter in the aneurysm that was intended for coiling did not fit concurrently within the guide catheter and was removed.
Operative technique
A 4×20 mm Hyperglide balloon was advanced through the existing PED. Once into the aneurysm, the balloon catheter was again navigated over the dome of the aneurysm, creating a large loop in the aneurysm before advancing into the MCA. The balloon was then inflated in the MCA and the balloon catheter was gently retracted. As the balloon was anchored in the MCA, the loop within the aneurysm was eliminated. With further traction on the balloon catheter, the portion of the PED that was within the aneurysm began to realign until the previously seen acute angle was eliminated. By re-opposing the PED to the ICA wall, a straight more direct path to the distal ICA was created without catheter redundancy within the aneurysm (figure 4). The balloon was kept inflated and the XT-27 microcatheter was then advanced directly into the MCA. After sufficient distal purchase was obtained with the XT-27, a second PED was advanced across the aneurysm to the end of the microcatheter before the balloon was deflated and removed. The second PED was then deployed without complication. Once again, incomplete expansion of the distal PED was seen, which was corrected without difficulty using balloon angioplasty.
(A, B) Posteroanterior and off-lateral working angle angiographic images demonstrating the withdrawal of the catheter loop and realignment of the distal end of the Pipeline Embolization Device using the balloon-anchoring technique. The white-appearing catheter is the location of the catheter prior to the maneuver, while the black-appearing catheter is the final catheter position following realignment using the balloon-anchoring technique. Reproduced with permission from Barrow Neurological Institute.
Results
Following successful realignment of the initial prolapsed PED using a balloon-anchoring technique, we were able to complete the embolization with placement of an additional PED. This provided complete coverage of the aneurysm and substantial flow stasis was seen immediately within the aneurysm (figures 5 and 6). The patient had an uneventful postoperative course and was discharged home on postoperative day 2.
(A, B) Unsubtracted working angle angiographic images demonstrating substantial flow stasis within the aneurysm following successful deployment of a second Pipeline Embolization Device. Reproduced with permission from Barrow Neurological Institute.
(A, B) Posteroanterior and lateral angiographic images taken at the completion of the procedure. The lateral image again shows substantial flow stasis within the aneurysm. Reproduced with permission from Barrow Neurological Institute.
Discussion
The use of the PED has been shown to be effective for the treatment of cerebral aneurysms.1–4 This success includes the treatment of large and giant aneurysms that otherwise may have suboptimal treatment options. Despite the potentially excellent results that can be seen with the PED, the device is not without potential complications.5
As is the case with any endovascular treatment, symptomatic complications occurring from thrombus formation or hemorrhage may arise from PED use. In addition, there are a number of potential complications that are more directly related to the deployment of the device. These may include incomplete expansion of the PED, the inability to deploy the PED due to tortuosity, or foreshortening or migration of the device which may result in incomplete coverage of the aneurysm, prolapse into the aneurysm or occlusion of the parent vessel.6–9 If managed effectively, these complications may remain clinically silent; however, if they are not dealt with appropriately, disastrous complications may result.
One factor that may complicate the delivery of a PED is the relative stiffness of the device, which may become a substantial issue in cases with significant tortuosity of the parent vessel. When such tortuosity is encountered, this may require a substantial amount of forward pressure on the PED in order to advance it to the point of desired deployment. When this tortuosity is seen within an aneurysm, the PED may not easily track within the microcatheter and instead the microcatheter may lose distal purchase. When planning the preferred location and course for PED deployment, the most direct path across the aneurysm is certainly desired but is not always attainable. Instead, creating prominent loops within the aneurysm may be required to achieve distal catheter purchase. Once distal catheter purchase is achieved, withdrawing the loop produces the most direct route across the aneurysm neck. This may be fairly simple or may require one of several techniques described in the literature. In 2007, Cekirge et al10 described using a balloon anchor in the distal artery in order to eliminate loops within a large aneurysm, and later descriptions included using balloon catheters, retrievable stents or even detachable coils.11–14 The general principle of all these techniques is that, by temporarily anchoring the microcatheter in the vessel distal to the aneurysm, the catheter can be retracted, removing the loop without losing purchase within the distal artery. After removing the loop within the aneurysm, treatment of the aneurysm is more straightforward either with stent placement or balloon remodeling.
In addition to the potential difficulty in traversing the neck of a large aneurysm, even after a PED is in place its stability may be tenuous. Depending on the proximal and distal purchase of the PED, prolapse of one end of the device into a large aneurysm may occur with any subsequent manipulation of the device, or even spontaneously. As was seen in our case, inflation of a balloon within the deployed PED was sufficient to cause prolapse of the distal end into the aneurysm.
In cases where a PED prolapses into an aneurysm, resultant flow diversion may be into the aneurysm rather than from the aneurysm and, therefore, the inability to rectify the situation will theoretically result in a substantially increased risk of rupture. In our particular case the prolapsed PED was directed towards the dome of the aneurysm, and repeated attempts to remove the microcatheter loop within the aneurysm were unsuccessful. This maneuver was made more difficult by the PED itself, which represented a relatively firm barrier that created an acute angle between the lumen of the PED and the distal ICA and prevented the microcatheter from straightening. Once it became apparent that an additional PED would not be successfully placed without manipulating the existing PED, the decision was made to attempt realignment of the PED using a balloon-anchoring technique. This maneuver ultimately proved to be successful, and allowed for placement of a subsequent PED and completion of the embolization.
Avoiding complications in the first place is, of course, preferable to successfully managing them once they occur. In the present case, complete deployment of the PED without areas of incomplete expansion would have avoided the need for balloon angioplasty, and subsequently would probably have prevented PED prolapse. In our experience, incomplete PED expansion is more likely to happen with longer devices such as 35 mm, but in this particular case it was felt that a shorter device would inadequately cover the neck and probably require multiple devices. Certainly the PED would have been less likely to prolapse if it had been deployed more distally along the ICA or into the proximal MCA. However, this would have covered additional branches and perforators that may not have been necessary. In retrospect, our attempt to balance minimizing branch/perforator coverage with adequate distal purchase was unsuccessful and more distal deployment might have averted our problems. Lastly, inflation of the balloon created enough force within the PED directed towards the aneurysm that prolapse occurred. It is possible that a less compliant balloon may have had less ‘watermelon seeding’ into the unprotected portion of the PED, which may have prevented this from occurring. An additional strategy could have been to inflate a balloon at the distal end of the PED prior to inflating the balloon across the proximal region of incomplete expansion. However, even in retrospect this may be considered a bit excessive.
Conclusion
Using a balloon anchor technique we were able to successfully realign an in situ flow-diverting stent that had prolapsed into a giant ICA aneurysm. Once the device was successfully realigned, embolization was completed without difficulty. This represents a useful salvage technique and should be considered when encountering a prolapsed stent.
References
Footnotes
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Contributors All authors contributed significantly to the work.
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Competing interests None.
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Provenance and peer review Not commissioned; externally peer reviewed.