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Abstract
Introduction Y-configured stent assisted coiling is a promising therapeutic option to ensure safe coil embolization and preserve the affected arteries in complex wide necked aneurysms. We present our experience with self-expanding Acandis Acclino stents for the treatment of complex aneurysms using the kissing-Y technique.
Methods We retrospectively reviewed seven patients with seven complex aneurysms (three anterior communicating artery (AcomA), two middle cerebral artery, one basilar artery/superior cerebellar artery, and one vertebral artery/posterior inferior cerebellar artery) who were treated with the kissing-Y technique by stent assisted coiling from June 2013 to July 2014, with follow-up until January 2015. DSA follow-up was up to 17 months, with a mean follow-up period of 10 months. Six patients were treated electively and one in the acute phase of a subarachnoid hemorrhage. In all cases, closed cell Acandis Acclino stents were used. We evaluated procedural complications, clinical outcomes, and mid term angiographic follow-up. Additionally, a literature review is provided.
Results In all patients, stents were successfully placed and implanted. One patient developed a periprocedural thromboembolic complication not directly related to the stents. No other periprocedural or postprocedural complications were encountered. Follow-up examinations showed stable and total occlusion of all coiled aneurysms.
Conclusions The results of our study show that the kissing-Y technique using closed cell Acandis Acclino stents followed by coil embolization is a feasible treatment option for selected complex bifurcation aneurysms.
- Aneurysm
- Device
- Intervention
- Stent
- Technique
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Introduction
Endovascular stent assisted coil embolization has become a widespread, safe, and effective method for the treatment of wide necked cerebral aneurysms. Stents have been shown to prevent coil protrusion out of the aneurysm sac into the parent vessel. Apart from keeping coils in place, using stents improves aneurysm occlusion rates due to the increased packing density and effective neck coverage compared with coiling alone.1
Particular attention is paid to bifurcation sites, where intracranial aneurysms occur more frequently because of the high hemodynamic shear stress and strong flow acceleration.2 Various stent configurations have been established for bifurcation sites. In addition to horizontal stent placement across the neck of a bifurcation aneurysm,3 the PCONus device,4 or the ‘waffle cone technique’,5 Y-configured stent placement has been shown to achieve good results in wide necked bifurcation aneurysms.6–9 The kissing-Y technique is an alternative endovascular treatment option.10 Kissing means the side by side placement of two microstents in the parent vessel, with the distal ends each in one bifurcation, with the advantage of obviating the need for passing a stent through the interstices of a recently deployed stent.11 Kissing-Y and crossing-Y stents with a closed cell design, compared with other configurations, show the strongest reduction in flow velocity in the aneurysm sac and redirection of the impingement flow.12
We report our experience and mid term clinical and angiographic follow-up results of seven complex bifurcation aneurysms treated with the kissing-Y technique using the new Acandis Acclino stents.
Material and methods
Patients
Patients with complex wide necked bifurcation aneurysms were included in the study. In every case, interdisciplinary discussion with the neurosurgical department took place. In addition to endovascular treatment, neurosurgery and conservative management were discussed with all elective patients. Written informed consent was obtained from all patients. Approval was obtained from the local hospital's institutional review board.
We retrospectively analyzed seven patients (mean age 61.4 years) who underwent endovascular treatment by the kissing-Y technique in our department between June 2013 and July 2014 with a follow-up until January 2015. Six patients were treated electively and one was in the acute phase of a subarachnoid hemorrhage. Five patients were treated with stent assisted coiling in one session. One patient was treated in a two step procedure, with initial stent placement followed by coil embolization 6 months later. One patient received only stents without subsequent coiling. One patient had previously undergone aneurysmal clipping and presented with aneurysm regrowth.
Aneurysms
Of the seven aneurysms, three were located at the anterior communicating artery (AcomA), two at the middle cerebral artery bifurcation, one at the basilar artery/superior cerebellar artery (SCA), and one at the vertebral artery/posterior inferior cerebellar artery (PICA) bifurcation. Aneurysm size ranged from 5 mm×7 mm to 15.5 mm×9.5 mm (largest diameters on biplane angiograms).
Premedication and anticoagulation
Prior to each procedure, dual antiplatelet therapy was administered. Acetylsalicylic acid (100 mg per day) and clopidogrel (75 mg per day) were used for premedication the week before endovascular therapy. Patients were not treated until adequate response to clopidogrel and acetylsalicylic acid was achieved. Sufficient inhibition of platelet function was confirmed by the Multiplate test. Measured values had to be below the reference standards. During the procedure, heparin was administered intra-arterially with close monitoring of activated clotting time, keeping it between 200 and 350 s. After endovascular treatment, all patients were prescribed 100 mg of acetylsalicylic acid and 75 mg of clopidogrel for a minimum of 1 year and 12 weeks, respectively. Three patients were already receiving 100 mg acetylsalicylic acid for other medical conditions.
Devices
We are the first to report on the kissing-Y technique using the Acandis Acclino stent system with a closed cell design (Acandis, Pforzheim, Germany). In six cases we used the Acandis Acclino 1.9 F stent system. In the last case, the new Acandis Acclino flex stent system was used. The self-expandable stents have a closed cell design and are resheathable and repositionable at a maximum of 90%. The laser cut stents have an electropolished surface. The flexibility and optimization for curved vessels constitutes an advantage concerning bifurcation aneurysms.
Stent specific diameters and lengths are listed in table 1.
Clinical data, aneurysmal localization, procedural characteristics, angiographic outcome, and complications of the included patients
Kissing-Y stent technique
All patients were treated under general anesthesia. A 6 F Envoy guiding catheter (Codman) was navigated into the internal carotid artery for aneurysms of the anterior circulation or in one vertebral artery if the posterior circulation was affected. Angiographic examination was carried out by a biplane angiographic system (Artis BA Biplane, Siemens, Erlangen Germany). Three-dimensional rotational angiography was used for accurate measurement of the aneurysm, understanding of the anatomical configuration, and to precisely plan the intervention. Two microcatheters (Acandis Acclino 1.9 microcatheter set or, in the case of the new Acandis Acclino flex stent system, the NeuroSlider 17 microcatheter) were advanced coaxially through the guiding catheter with the use of different microguidewires to the aneurysm site, with one tip in each efferent bifurcation branch. When positioned correctly, the guidewires were withdrawn and two appropriate Acandis Acclino 1.9 microstents were sequentially advanced through the microcatheters and under roadmap guidance, simultaneously deployed from the distal end of the efferent vessels to the bifurcation, and in a parallel ‘kissing’ fashion from the distal to the proximal portion of the parent vessel. Deployment was performed by unsheathing the stents alternately, millimeter by millimeter. Subsequently, one microcatheter was withdrawn. Stent deployment was followed by sequential coiling of the aneurysm sac.
No difficulty in navigating back through the closed cell Y-stent construct was observed.
Coiling
One of the microcatheters previously used for stent deployment or an Echelon 10 microcatheter was navigated through the interstices of the kissing-Y stents into the aneurysm and detachable coils (Axium: 3D, Helix; and Axium Prime: 3D, Helix; Covidien) were inserted.
Occlusion grade, and clinical and angiographic follow-up
The Raymond–Roy Occlusion Classification was used as the standard for evaluating coiled aneurysms.13 DSA follow-up was up to 17 months. At discharge and follow-up, neurological status was scored using the modified Rankin Scale (mRS).14
Literature review
In addition to our cases, we performed a literature review of reported cases of intracranial aneurysms treated with the kissing-Y technique. We searched in the PubMed database and used the following keywords in various permutations: ‘kissing Y’, ‘kissing stents’, ‘double barrel stent’, ‘parallel stents’. There were no study design restrictions. The literature search yielded more than 500 articles.
Articles were excluded for the following reasons: publication in cardiology journals; kissing-Y technique performed in technical models and not in patients; and X-configured kissing stents were described.
Results
Aneurysmal localization, angiographic outcome, and clinical complications are summarized in table 1.
Technical performance and complications
In our series, stents were successfully established using the kissing-Y technique in all patients. There were no technical difficulties with the kissing-Y method related to stent deployment or insertion of the coils. However, one complication was noted in a patient who suffered from thromboembolic events during the intervention, managed by administration of tirofiban. CT scan 1 day after the procedure revealed infarctions in the right anterior circulation and in the left PICA territory. There was no fetal origin of the posterior cerebral artery. The other six patients showed no post-interventional complications or neurological deficits related to the procedure.
In one case, stent deployment and coiling were performed on two separate occasions.
In the case of an aneurysm located at the basilar artery between one P1 segment and the SCA, with the SCA rising directly out of the aneurysm fundus, only stents were placed. We preferred not to insert coils because of the risk of artery occlusion.
Immediate embolization results and DSA follow-up
Mean angiographic follow-up time was 10 months. In four patients, the follow-up period was more than 12 months, in two patients 6 months, and in one case the relatives refused further investigations. Follow-up showed complete occlusion in all coiled aneurysms. Occlusion was accomplished without disturbance of the physiological circulation. No in-stent stenosis or symptoms were observed in patients where antiplatelet therapy was stopped (after 12 months). In cases where we avoided coiling the aneurysm after kissing-Y stenting, follow-up angiography showed delayed inflow and outflow in the aneurysmal fundus. Five patients had an mRS score of 0 at discharge and follow-up. One patient (case No 4) suffering from brainstem compression remained at an mRS score of 1. One patient (case No 5) had an mRS score of 4 at follow-up. Neither mortality nor procedure related bleeding occurred during the follow-up period. None of the patients developed regrowth of the aneurysm (up to this point).
Illustrative cases
Case No 3
An elderly patient presented with a large wide necked aneurysm of the AcomA, incidentally found on an MRI brain scan. DSA showed a fusiform wide necked aneurysm of the AcomA bifurcation measuring 7 mm×5 mm (figure 1) with the left A1 segment supplying both A2 segments. There was no supply from the right A1 segment. This discovery was the reason for protecting the affected vessels with stents before inserting coils, which otherwise would bear the risk of vessel occlusion. We simultaneously deployed two Acandis Acclino stents using the kissing-Y technique from both A2 down to the left A1 segment (figure 2). The aneurysm sac was subsequently coiled with four coils (Axium Prime; Covidien) (figure 3).
DSA, left internal carotid artery injection, frontal (A), with three-dimensional rotational angiography in the working projection (B), showing a wide necked 7×5 mm aneurysm of the anterior communicating artery.
Non-subtracted frontal (A) and lateral (B) views of the simultaneous positioning of the two stent systems from the left A1 into both A2 branches before deployment.
Non-subtracted frontal (A) and lateral (B) views showing the deployed stents with their markers and coils.
Post-interventional cranial CT demonstrated no evidence of intracranial hemorrhage or ischemic lesions. Angiograms after 6 and 12 months of follow-up showed complete occlusion of the aneurysm sac and no evidence of recurrence (figure 4).
DSA, frontal view, before (A) and after (B) Y-stent assisted coil embolization of an anterior communicating artery aneurysm. Note the flattening of both A1/A2 angles (arrows).
Case No 4
A patient presented to our department with brainstem syndrome. Cranial CT and MRI revealed a partially thrombosed and calcified giant aneurysm of the left PICA/V4 segment, measuring 25 mm×23 mm (figure 5). The brainstem signs, in particular staggering vertigo, double vision, tendency to fall to the left side, and nausea, were due to the mass effect of the aneurysm on the medulla oblongata and the pons. DSA showed a dysplastic wide necked aneurysm of the left PICA/V4 segment, measuring 9 mm×7 mm, with the origin of the left PICA directly out of the aneurysm sac (figure 6). Initially, a 3.5×35 mm Acandis Acclino stent was deployed from the left proximal PICA to the left providing proximal V4 segment. At the same time, a second microcatheter was placed in the V4 segment. Simultaneously, the second stent (4.5×25 mm) was deployed, bridging the basis of the aneurysm and running side by side with the other stent in the proximal V4 segment (figure 7). In this way, influx to the PICA was protected.
Cranial CT (A) and sagittal T2 weighted MRI (B) showing a partially thrombosed and calcified giant aneurysm of the left posterior inferior cerebellar artery/V4 segment.
DSA frontal (A) and lateral (B) views, left vertebral artery injection, showing a dysplastic wide necked aneurysm of the left posterior inferior cerebellar artery (PICA)/V4 segment, measuring 9 mm×7 mm, with the origin of the left PICA directly out of the aneurysm sac.
DSA in working projection. Initially, a 3.5×35 mm Acandis Acclino stent (white arrow indicating the distal stent markers) was deployed from the left proximal posterior inferior cerebellar artery to the left providing V4 segment. Then, a 4.5×25 mm stent (black arrow) was placed in the V4 segment, bridging the basis of the aneurysm and running side by side with the other stent in the proximal V4 segment.
Six months after initial kissing-Y stenting, coil embolization was performed using four detachable coils (Axium Prime; Covidien) (figure 8). Post-interventional CT showed no signs of bleeding or stroke. MR angiography showed no in-stent stenosis, no reperfusion of the aneurysm sac, and total exclusion of the aneurysm from the circulation.
DSA frontal (A) and lateral (B) views, left vertebral artery injection. Six months after initial stent placement, complete coil embolization was performed using four detachable coils.
At 12 months, angiography showed stable and total occlusion of the aneurysm and no disturbance of the circulation. The PICA remained patent on follow-up.
Results of the literature review
In a total of six articles, the kissing-Y technique, meaning parallel deployment of stents, was performed in cases of complex intracranial aneurysms.10 ,11 ,15–18 Table 2 shows the collected data. A total of 16 patients were evaluated. Mean age of the patients was 56 years. In two cases, aneurysms were located at a fenestrated vertebrobasilar junction. In these patients, two flow diverter stents were advanced using the kissing technique. In all other cases, either the Neuroform (Boston Scientific) or the Enterprise (Cordis) stent, or a combination of both, were used. Stent implantation and coiling was successful in 14 of 16 cases. Further treatment was required in two cases. The overall mortality in the stated follow-up period was 2 of the 16 cases.
Published cases of kissing-Y stenting
Discussion
In this study, we evaluated the results of the treatment of wide necked bifurcation aneurysms by the kissing-Y technique using Acandis Acclino stents, followed by coil embolization.
There were no technical complications from stent deployment itself. We observed one periprocedural complication and no mortality. One patient had thromboembolic complications managed with tirofiban. We suspected a cardiac source of the embolism. After a mean observation period of 10 months, angiographic follow-up showed stable and total occlusion of the aneurysms in all coiled patients. None of the patients has required retreatment (up until this point).
Double stent assisted coiling for bifurcation aneurysms is a treatment option when the branching arteries cannot be preserved otherwise, when there is no identifiable neck, or when the aneurysm cannot fully be packed with coils.6 Particularly in the case of aneurysms in the vertebrobasilar circulation, we did not consider flow diversion as a treatment option due to a possible risk of perforator occlusion or occlusion of the PICA origin.
The Y-configuration is subdivided into different techniques. Crossing-Y describes deployment of a second stent through the interstices of a previously placed stent. There have been difficulties in individual cases when delivering the second stent through the interstices of the first stent used with this technique.19 In other cases, closed cell design stents were used in the crossing-Y technique. Deployment of the second stent through the struts of the first stent is prone to failure.6 The idea of the kissing-Y technique is that there is no overlap of stents, presumably reducing the risk of interfering with blood flow. In contrast, the stents might optimize flow diversion by reducing inflow into the aneurysm.
To the best of our knowledge, we are the first to demonstrate the treatment of a V4/PICA aneurysm using the kissing-Y technique. To date, there have been no reports of the kissing-Y technique using the Acandis Acclino stents. We observed no difficulties using these stents. The closed cell design stents are resheathable and can be repositioned if mandatory.
Jankowitz et al11 described a three microcatheter system with one stent delivery device advanced into each bifurcation. The third microcatheter was located with the tip in the aneurysm fundus. We did not encounter any complications in the deployment of stents as a first step or following insertion of coils with a catheter navigated through the interstices of the kissing stents in the aneurysm sac. A microcatheter for sequential coiling trapped between two stents may incur the risk that it cannot be removed easily. Additionally, multiple catheters placed simultaneously in one vessel carry a higher risk of thromboembolism and a reduction in physiological flow to the corresponding territories.
It was interesting that in their case series, Jankowitz et al presented a second deployed stent that remained collapsed or only partially expanded in the proximal vessel. We deployed the stents millimeter by millimeter alternately to prevent collapse of one stent. Unfortunately, in our angiography suite, we had no way of evaluating eventual collapse using this technique. Further research using, for example, high quality Dyna-CT, would be of interest.
Gao et al used computational fluid dynamic analysis to assess the effects on cerebrovascular remodeling of stent assisted coiling in the Y-configuration in basilar bifurcation aneurysms. Y-stenting decreases the angle between the P1 segments of the posterior cerebral arteries, straightening and narrowing the bifurcation. Furthermore, it significantly narrows the wall shear stress systolic interpeak at the apex, redirecting the stress away from the neck to the inert coil mass. Longer follow-up showed that stents delayed angular remodeling. The effect was even greater in the kissing stent configuration than in the crossing configuration.20 Gao et al also measured the angle between mother and daughter vessels in different stent designs. They suggested that the bending force of stents leads to a straightening of the vessel bifurcation. The angular remodeling seemed more pronounced with closed cell design stents. In follow-up controls, the angle continued to expand due to angular remodeling.21 Unfortunately, we did not perform preoperative three-dimensional rotational angiography in all patients for exact measurements and statistical assessment. However, we observed an angular remodeling when using exactly the same working projection (example shown in figure 4).
In one case, we did not insert coils because of the risk of occlusion of the SCA arising out of the fundus of the aneurysm. However, control angiography at 4 months and at 17 months showed a reduction of the inflow and outflow to the aneurysm fundus (figure 9).
DSA frontal view, vertebrobasilar injection. (A) Complex right sided basilar artery (BA)/superior cerebellar artery aneurysm. (B) Forward displacement of the bifurcation point (arrow) after kissing-Y stenting from the BA to both posterior cerebral arteries. Note also reduced inflow to the aneurysm.
Kono and Terada showed that kissing-Y and crossing-Y stents provide the strongest reduction in flow velocity in the aneurysm sac in a silicone model. They postulated that the narrowed strut structure of closed cell stents may decrease recanalization by reducing flow velocity in the aneurysm sac.12 In our study, using the new closed cell Acandis Acclino stents, no recanalization has been detected after more than 12 months of follow-up.
Limitations
Limitations of our study include the retrospective study design and the small number of cases.
Conclusion
The results of our study show that the kissing-Y technique using closed cell Acandis Acclino stents followed by coil embolization is a feasible treatment option for selected complex bifurcation aneurysms. The kissing-Y technique should be reserved for severe and complex bifurcation aneurysms when a single stent does not provide adequate protection of the bifurcation branches.
References
Footnotes
FB and KM contributed equally as joint first authors.
Contributors FB: conceptualized the study; drafted the initial manuscript and revised it critically, and approved the final manuscript as submitted. KM: acquired, analyzed, and interpreted the data for the work; designed the study; drafted the manuscript and approved the final manuscript as submitted. MS-H: acquired, analyzed, and interpreted the data for the work; revised the manuscript and approved the final manuscript as submitted. DM: acquired, analyzed, and interpreted the data for the work; critically revised the manuscript and approved the final manuscript as submitted. All authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Competing interests None declared.
Ethics approval Approval for the study was obtained from the local hospital's institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The authors agree to share data on request.