Background The Pipeline embolization device (PED) is a braided flow diverter that requires a combination of meticulous maneuvers to assure proper device opening and expansion. Mechanical, anatomical, or technical challenges can result in a partially deployed PED with failed expansion.
Objective To present a new alternative method of PED deployment using the Navien distal intracranial catheter (DIC) as a salvage maneuver for cases where PED opening fails with standard techniques.
Methods We retrospectively reviewed a prospective, single-center aneurysm database to identify all patients who underwent endovascular treatment of intracranial aneurysms using the PED with the Navien distal intracranial catheter access platform. Cases requiring PED deployment within the Navien catheter were reviewed. Data was collected for patient demographics, aneurysm characteristics, and technical details of the interventional procedure.
Results Eleven PED neurointerventions requiring intra-Navien PED deployment to fully open the PED were identified. Mean patient age was 55.5±9.9 years (range 37–76 years). Mean aneurysm size was 12.5 mm±4.9 mm (range 2–42 mm). All aneurysms were located in the anterior circulation (anterior cerebral artery, n=1; supraclinoid, n=1; ophthalmic/paraophthalmic, n=6; cavernous, n=3; petrocervical, n=1). Mean fluoroscopy time was 67.1±20.5 min. The intra-Navien technique was used to open the proximal PED (n=7) and the mid-portion (n=4). Post-processing of the PED with a balloon was used in six cases.
Conclusions When a partially deployed PED remains constrained despite exhaustion of standard maneuvers to facilitate opening, the technique of intra-Navien PED deployment is a valuable rescue strategy. This new alternative method of PED deployment can be used to open a stretched device with successful completion of the PED implantation.
- Flow Diverter
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Considerable experience in flow diversion with the Pipeline embolization device (PED) has accumulated since the USA Food and Drug Administration (FDA) approval of PED in 2011. This represents a paradigm shift in the management of intracranial aneurysms from an approach of endosaccular occlusion to endoluminal reconstruction. PED use has now extended beyond the on-label indications to small internal carotid artery (ICA) aneurysms,1 ,2 posterior circulation aneurysms,3 dissecting aneurysms,4 anterior cerebral artery aneurysms,5 and middle cerebral artery aneurysms.6
Along with transforming the treatment paradigm for cerebral aneurysms, flow diversion with PED has introduced a new technique to the neurointerventional space. Although PED is labeled a ‘device’, its deployment is unlike that of other commercially available intracranial stents. Traditional intracranial stents used in cerebral aneurysm treatment are nitinol self-expanding stents (Neuroform and Enterprise). By contrast, the PED is a braided cobalt–chromium mesh requiring a combination of maneuvers to assure proper device opening and expansion. In certain circumstances, mechanical, anatomical, or technical challenges can hinder appropriate PED opening and vessel wall apposition, resulting in a stretched device. For example, when the PED coil tip and delivery wire are not able to advance forward, the PED cannot fully expand and becomes stretched with attempts to deploy the device by a pushing technique. Additionally, moderate to severe tortuosity of the cavernous ICA has been observed to limit the ability of larger diameter PED devices to fully open with standard deployment maneuvers.
Despite the prevalence of PED neurointerventions and its believed association with complications, few reports have been published on the management of intraprocedural PED deployment challenges and potential bailout or rescue strategies.7 ,8 We present a new alternative method of PED deployment using the Navien distal intracranial catheter (DIC) as a salvage maneuver for cases when PED opening fails with standard techniques.
Patients and methods
We retrospectively reviewed a prospective, single-center aneurysm database identifying all patients who had undergone endovascular treatment of intracranial aneurysms using the PED with the Navien DIC access platform. Cases requiring PED deployment within the Navien catheter were identified.
Embolization procedures were performed as previously described.2 ,9 Briefly, all patients were treated preoperatively with a dual antiplatelet regimen consisting of aspirin 325 mg daily and clopidogrel 75 mg daily for 7 days before the intervention. The degree of P2Y12 receptor inhibition was not routinely tested. All procedures were performed with systemic anticoagulation using heparin with a 5000 U bolus at the start of each case followed by an intraprocedure re-bolus of 1000 U at each additional hour. A triaxial system was used through femoral access. This consisted of a 6 French Flexor Shuttle sheath (Cook Medical, Bloomington, Indiana, USA) or an 8 French 088 Neuron MAX delivery catheter (Penumbra, Alameda, California, USA), a 5 French 058 Navien DIC (Covidien Vascular Therapies, Mansfield, Massachusetts, USA) and a Marksman microcatheter (Covidien Vascular Therapies, Mansfield, Massachusetts, USA). The distal PED was opened in the ipsilateral ICA or, more commonly, in the ipsilateral M1 segment for aneurysms located along the intracranial ICA. Proper device expansion and deployment was assessed with native fluoroscopy. PED was deployed with a combination of unsheathe and push maneuvers. The Marksman and PED were moved synchronously forwards and backwards along the inner and outer curvatures (‘wagging’) to facilitate PED expansion and vessel wall apposition during deployment.
Intra-DIC PED deployment technique
When the PED failed to progressively open and remained stretched in these cases despite exhausting standard salvage maneuvers, the intra-Navien DIC technique was used. In this technique, the Navien was first advanced over the Marksman to the unopened part of the PED. The PED was then fully unsheathed within the Navien catheter, releasing the PED from the delivery wire. At this point, the Marksman functioned as the delivery ‘wire’ or pusher and the Navien functioned as the Marksman or delivery microcatheter. PED deployment and opening then proceeded with a combination of unsheathe from the Navien and push on the Marksman. The Navien and Marksman were intermittently wagged back and forth to facilitate the vessel wall apposition of the PED. This wagging is similar to the classic deployment technique. Fluoroscopic sequences of the intra-Navien deployment were saved and converted to video format to help illustrate the technique.
Control digital subtraction angiography was performed immediately after deployment and at 5 and/or 10 min after deployment to confirm patency of the parent vessels and to rule out intraluminal thrombus. In cases that required post-processing of the implanted PED, a TransForm balloon (Stryker Neurovascular, Fremont, California, USA) or HyperGlide balloon (Covidien Vascular Therapies, Mansfield, Massachusetts, USA) was used.
Data on patient demographics, aneurysm characteristics, proximal tortuosity, procedural equipment, and technical details were collected. Factors assessed for proximal tortuosity included aortic arch type,10 cervical ICA tortuosity (defined as a 90° turn, hairpin turn, or corkscrew loop), and cavernous ICA grade.11 Data were presented as counts.
Patient and aneurysm characteristics
Two men and nine women were treated. Mean patient age was 55.5±9.9 years (range 37–76 years). A total of 12 aneurysms were treated (one patient had two neighboring aneurysms). All aneurysms were located in the anterior circulation with the majority (6/12) being ophthalmic or paraophthalmic. Mean aneurysm size was 12.5 mm±4.9 mm (range 2–42 mm).
Proximal vascular access characteristics
Indicators of proximal access complexity and procedural challenges include aortic arch type, cervical ICA tortuosity, and cavernous ICA grade. A type I aortic arch was seen in one case, type II in five cases and type III in one case. Four cases had undocumented arch types. Cervical ICA tortuosity was defined as a 90° turn, hairpin turn, or corkscrew loop. This was significant in three cases. There was a spectrum of cavernous ICA tortuosity: type IA (n=1), type IB (n=1), type II (n=4), type IV (n=4).
A single PED was used in eight cases. The three cases requiring multiple PEDs were a large fusiform cavernous aneurysm, a giant serpentine anterior cerebral artery aneurysm and a large cervical ICA dissecting aneurysm. Mean heparin dose for the 11 cases was 5700±1400 U. Mean fluoroscopy time was 67.1±20.5 min. The intra-Navien technique was used to open the proximal end of the PED in seven cases, and the mid-portion in four cases. The cavernous ICA was the most common location where intra-Navien PED deployment occurred (9/11). In a majority of the cases (9/11), PED sizes were ≥4 mm in diameter. Balloon post-processing of the PED was required in six cases.
Case illustration 1
During a stroke investigation, a sexagenarian patient (case No 3) was found to have a 6 mm supraclinoid ICA aneurysm. The case is illustrated in detail in figure 1 and online supplementary video 1. A PED sized 4×20 mm was opened and well-apposed at its distal end in the supraclinoid ICA. While deploying the device around the anterior genu, the PED failed to open despite wagging the Marksman and PED. The device was stretched around the bend of the anterior genu secondary to inability to advance the distal end of the delivery wire in the middle cerebral artery. The intra-Navien technique was then used to complete the PED deployment. The PED was first fully unsheathed within the Navien catheter. Sequential pushing on the Marksman positioned at the distal end of the PED with unsheathe of the Navien, allowed the PED to open fully around the anterior genu (see online supplementary video 1). The Navien and Marksman were wagged back and forth to facilitate the vessel wall apposition of the PED. The final deployed PED was well apposed throughout and did not require any balloon post-processing.
Case illustration 2
During evaluation of a syncopal episode, a septuagenarian patient (case No 8) was found to have a 19 mm paraophthalmic aneurysm. Figure 2 demonstrates the type IV cavernous ICA tortuosity and highlights the sequence of PED deployment. A 4.5×25 mm sized PED was initially open and well apposed at the distal end. Midway through deployment, the device failed to open and appeared stretched. This occurred while attempting to deploy the device along the anterior genu and was attributed to an inability to push the distal delivery wire forward. The intra-Navien deployment was then used by first fully unsheathing the PED within the Navien catheter. Opening of the proximal portion of the PED was then achieved after pushing on the Marksman with unsheathe of the Navien. The proximal PED end was further opened and expanded by bumping with the Navien. This resulted in significant foreshortening of the PED with a fully opened and well-apposed proximal end. There was narrowing of the mid-portion of the PED at the anterior genu, which was ballooned open with a HyperGlide 4×20 mm.
Case illustration 3
During routine imaging performed for melanoma follow-up, a sexagenarian patient (case No 7) was found to have a 7 mm paraophthalmic aneurysm. The case is illustrated in detail in figure 3 and online supplementary videos 2–3. A PED sized 4.5×16 mm was opened and well apposed at its distal end in the supraclinoid ICA. The larger diameter PED exhibited ‘laziness’ in opening around the posterior genu and failed to fully expand. The intra-Navien technique was then used to complete the deployment of the proximal end. Online supplementary video 2 demonstrates the opening of the proximal end of the PED with the intra-Navien technique and online supplementary video 3 shows further expansion with improved vessel wall apposition by bumping with the Navien. The final deployed PED was well apposed throughout and did not require any balloon post-processing.
We present in this report the novel technique of intra-Navien DIC PED deployment. This method was used in 11 PED cases where standard maneuvers failed to produce proper sequential PED opening and resulted in an incompletely expanded and stretched device. In all but two of these cases, PED sizes used were ≥4 mm (larger PED sizes are known to have more difficult device openings as a result of the uniform 48-strand device design across all PED diameters). The intra-Navien technique was used to open the proximal end of the PED in seven cases, and the mid-portion in four cases. The cavernous ICA was the most common location for which intra-Navien PED deployment was used (9/11). Most cases (8/11) had moderate (grade II) to severe (grade IV) tortuosity of the cavernous ICA. In almost half the cases (5/11), the intra-Navien technique alone was sufficient to fully open and appose the stretched device without requiring any additional balloon post-processing.
With the classic techniques of PED deployment, proper PED opening is coupled to the forward/distal movement of the coil tip. This allows the device to fully expand and appose to the vessel wall. When the coil tip and delivery wire are not able to advance forward, the PED cannot fully expand and becomes stretched with attempts to deploy the device by a pushing technique. The intra-Navien PED technique provides a solution to this challenge. Once PED deployment fails with standard maneuvers, the PED is fully unsheathed within the Navien catheter. This releases the device from the delivery wire, which results in a deployment strategy that is similar to one used for the Surpass Flow Diverter (Stryker Neurovascular, Fremont, California, USA). Since the PED is completely free from the delivery wire, progressive opening of the device becomes independent of the delivery wire distal migration. This then allows the forces applied for the deployment to be transmitted primarily to the device itself rather than the PED-delivery wire unit. In this technique, the Marksman functions as the pusher and the Navien functions as the Marksman or delivery microcatheter. PED deployment and opening then proceeds with a combination of unsheathe from the Navien and push on the Marksman. Using this technique, the Navien DIC becomes the workhorse for the PED deployment and apposition.
Few reports have been published on the management of mechanical or technical challenges that can hinder appropriate PED deployment. Navarro and colleagues described a case report of a radical salvage technique for failed PED expansion during deployment.8 In their case, the partially deployed PED was accessed by an SL10 microcatheter in a retrograde fashion via contralateral access of the anterior communicating artery. An intracranial exchange was then performed to introduce a Hyperform balloon. However, given significant tortuosity, the authors reported difficulty in advancing the balloon. They subsequently described a flossing technique where a microsnare was advanced through the ipsilateral side to stabilize the microwire in the balloon and the balloon was then advanced over the microwire to the constricted proximal end of the PED. Compared with these rescue strategies, the intra-Navien PED deployment avoids the complexity of contralateral access, intracranial exchange, and manipulations across a potentially fragile anterior communicating artery. This minimizes the added intraprocedural risks, particularly in cases with tortuous anatomy.
Additional salvage techniques include corking and pseudo-corking for removal of a malpositioned or stretched device. We have previously described these two techniques in detail.7 The corking maneuver requires an intact pusher wire that is withdrawn to the point where the protective/capture coil engages the PED as it exits the distal microcatheter. This act pins the partially deployed PED against the distal microcatheter lumen and the PED protective/capture coil serves as the ‘cork’. However, late in deployment of the PED the corking maneuver can be fraught with risk as the forces required to overcome the friction of the deployed device against the vessel wall can lead to fracture of the delivery wire. If the pusher wire is fractured, the pseudo-corking rescue strategy can be used and requires a more complex series of maneuvers. The DIC is first advanced over the Marksman catheter until both the tips are nearly aligned to provide maximum support to the Marksman. The Marksman catheter is then advanced forward to jam into the proximal end of the partially deployed PED. Afterwards, the Marksman (with the PED) is carefully withdrawn into the DIC. Once the Marksman is inside the DIC, the DIC and Marksman are withdrawn as a unit with the PED inside. Compared with corking and pseudo-corking, the technique of intra-Navien PED deployment allows efficient rescue of the in situ PED rather than complete removal of the device. In our experience with this technique, the stretched PED was successfully opened in all 11 cases. Additionally, in almost half the cases, balloon post-processing was not needed after completing PED deployment with the intra-Navien technique. This was perceived to be both a safe and cost-effective strategy.
Recently, the new-generation PED, Pipeline Flex, has become available. This has the advantage of resheathability, which the first-generation PED lacks. Rather than obviating the need for intra-Navien PED deployment, the resheathability feature replaces the corking and pseudo-corking techniques. However, with Pipeline Flex, proper PED opening is still coupled to the forward/distal movement of the delivery wire. In addition, the design of the PED implant consisting of uniform 48 strands across all PED diameters remained unchanged with the Pipeline Flex. For these reasons, we have still found that intra-Navien PED deployment is a prudent strategy with Pipeline Flex cases. In this report, Pipeline Flex was used for two of the 11 cases. In both these cases, the PED diameter used was 4.25 mm. The moderate to severe tortuosity of the cavernous ICA observed in both cases limited the ability of these large-diameter devices to open fully with standard maneuvers. When these devices failed to expand fully mid-deployment, we converted to the intra-Navien PED deployment technique.
We attribute the success of the intra-DIC PED deployment technique to the trackability of the Navien DIC. The Navien belongs to a newer class of hybrid nitinol-braided distal access catheters designed in the era of flow diversion. Compared with other commercially available distal access catheters, the larger inner bore and hyperflexible nature of the Navien catheters provide significant advantages which make it a superior platform for PED deployment.12–14 In our experience with the Navien catheter in >300 PED cases, we routinely used the extreme trackability of this catheter throughout deployment. In the beginning, the catheter is taken distally to give support and to optimize push and distal end opening. Towards the end of deployment it often serves as a tool to foreshorten the proximal end to obtain perfect vessel apposition. It is from the routine and safe use of this catheter and for these reasons that the technique of intra-Navien deployment presented in this report was developed.
Deployment of the PED requires a combination of meticulous maneuvers to assure proper device opening and expansion. In certain circumstances, mechanical, anatomical, or technical challenges can hinder appropriate device expansion. In these situations, the technique of intra-Navien DIC PED deployment is a valuable rescue strategy that can be used to open the stretched device and successfully complete the PED deployment.
Contributors L-ML drafted the manuscript and critically revised the manuscript for important intellectual content. GPC assisted in critically revising the manuscript. BJ assisted with the data collection and analysis. NN helped to draft the manuscript. JH and RJT critically reviewed the important intellectual content. ALC conceived the idea and critically reviewed the important intellectual content. All authors read and approved the final manuscript.
Competing interests ALC is a proctor for the Surpass device (Stryker Neurovascular, Fremont, California, USA) and a consultant for Stryker Neurovascular, a proctor for the Pipeline embolization device (Covidien, Mansfield, Massachusetts, USA) and a consultant for Covidien, and a proctor for the FRED device (Microvention, Tustin, California, USA) and consultant for Microvention. GPC is a consultant for Covidien and Microvention. The other authors have no conflict of interest.
Ethics approval This study was conducted with the approval of the Johns Hopkins Medicine institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.