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|NI FEATURE: THE EDITORIAL DEBATE II-- PROS AND CONS
|Year : 2018 | Volume
| Issue : 1 | Page : 43-45
Endovascular management of vertebral artery dissecting aneurysms
Vipul Gupta, Rajsrinivas Parthasarathy
Department of Interventional Neuroradiology, Artemis Agrim Institute of Neurosciences, Gurgaon, Haryana, India
|Date of Web Publication||11-Jan-2018|
Dr. Vipul Gupta
Department of Interventional Neuroradiology, Artemis Agrim Institute of Neurosciences, Gurgaon, Haryana
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gupta V, Parthasarathy R. Endovascular management of vertebral artery dissecting aneurysms. Neurol India 2018;66:43-5
Vertebral artery dissecting aneurysms presenting with hemorrhage carry a poor outcome if left untreated, with an early repeat hemorrhage in 70% of cases and a high mortality of 46.7% in those patients with a repeat rupture. Therefore, an early treatment is required to prevent a repeat rupture. In this issue, Chinchure et al., have described their experience of treating ruptured vertebral artery dissecting aneurysms by both deconstructive and reconstructive techniques.
The authors favored the technique of trapping of the parent vessel in patients with a contralateral dominant/co-dominant vertebral artery. Though an effective technique, the possible challenges with this technique are that of migration of coil, under-packing, symptomatic infarction and rebleed. Symptomatic infarction in the territory of the occluded artery that is directly related to the procedure has been reported to occur in approximately 5.3% of patients with endovascular trapping, with a repeat hemorrhage rate of 3.1%. However, in our experience, in appropriately selected patients, trapping appears to be a safe and effective technique and we have not encountered any incidence of symptomatic infarction or re-bleeding in our patient group. The authors of the paper tended to use oversized coil in order to prevent distal migration. However, oversizing of the coils in a ruptured dissecting aneurysm may perhaps increase the risk of rupture during the procedure. Therefore, one of the options that can be considered under such circumstances is to use dual microcatheters to avoid distal coil migration and, in addition, achieve better packing and occlusion [Figure 1]. In our practice, to avoid distal embolism, we maintain adequate heparinization during the procedure. In addition, following coil occlusion, we administer heparin for a short period, approximately 48 hours, and follow it up with administration of aspirin alone for 6-weeks. To avoid an episode of rebleeding, we advocate trapping of the segment of the vessel that is involved with the dissection and also occlude a very short segment of the proximal normal parent artery.
|Figure 1: (a) A 50-year old male patient with subarachnoid hemorrhage and dissecting aneurysm of the right V4 segment vertebral artery. (b-d) The dual microcatheter technique: Two microcatheters are placed one at the distal part of the sac and the other at the proximal end of the sac. The first coil is deployed through the distally placed catheter. The coil is not detached and further coils are placed through the proximal catheter. The coil in the distally placed microcatheter is not detached until such time that a stable coil mass has been achieved through the proximal catheter. Also, the distally placed coil allows for packing of the distal end of the sac so that there is no retrograde filling of the aneurysm sac. (e) The parent artery is occluded. (f) Retrograde filling of the right vertebral artery distal to occlusion occurs along with some stasis; therefore, we prefer commencing on short term heparin course followed by antiplatelet agents. This technique is suitable for in patients with co-dominant or dominant contralateral vertebral artery and when the PICA or perforators are not arising from the aneurysm sac|
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The two factors that would dissuade the doctor from trapping the parent vessel are:First, if the contra-lateral vertebral artery is hypoplastic; and, second, if any critical artery such as the posterior inferior cerebellar artery (PICA), anterior spinal artery or medullary perforators arise from or are in close proximity to the dissected segment. Symptomatic infarction has been noted in about 38% of the patients if trapping is performed in patients in whom the PICA arises from the dissected segment; however, others have reported a good outcome even in this group of patients and have attributed it to good pial collaterals. The authors of the paper have performed proximal occlusion in one patient in whom the PICA arose from the dissected segment. However, this approach is not without drawbacks, the key disadvantage being the possibility of a repeat bleed that has been reported to occur in about 19% of patients.
Reconstructive techniques are better suited for the aforementioned patient category. Furthermore, endoluminal reconstruction appears to be the most appropriate strategy in unruptured aneurysms, particularly due to the low risk of acute bleeding. According to a meta-analysis, although sac occlusion was better with trapping, the perioperative morbidity and mortality, recurrence and retreatment rates, and long-term clinical outcome were similar with both the deconstructive and reconstructive techniques. Single stent with coils, overlapping stents, and flow diversion are the reconstructive techniques that have been described in literature. Stent-assisted coiling is an effective method to treat such aneurysms; however, it is at times technically challenging, and we advocate using multiple small coils to pack the sac in order to avoid an extraneous outward pressure that can result in aneurysmal wall rupture. In our experience and according to previous reports, stent assisted coiling appears to be less effective than trapping in achieving a long-term aneurysmal occlusion in dissecting fusiform aneurysms and some of these patients need further treatment after the primary procedure. The authors have used a single stent with coils and have not documented recurrence rates on a long-term follow up. Therefore, one may wish to use a stent within a stent. Overlapped sents, by introducing better flow diversion, promote thrombosis and enhances sac occlusion [Figure 2]. The stent type utilized in the procedure may play an important role in the effectiveness of the procedure and is discussed further.
|Figure 2: (a) A 40-year old female patient admitted with subarachnoid hemorrhage was noted to have a dissecting aneurysm involving the V4 segment of the left vertebral artery. (b) The three-dimensional rotational angiography showing the left V4 vertebral artery dissecting aneurysm; note the origin of left PICA proximal to the aneurysm along with a non-dominant contralateral vertebral artery. (c) Microcatheter with a few coil loops were deployed within the aneurysm sac prior to deployment of a laser cut stent. (d and e) Multiple small coils were deposited and were followed by deployment of a second laser cut stent within the previous one. Note the circumferential coils around the stent. (f) On follow up, complete occlusion of the aneurysm sac occurred along with straightening of the V4 segment of the vertebral artery|
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Braided stents are likely to offer better redirection of flow as compared to laser cut stents. In an experimental model, Wang et al., were able to demonstrate better flow diversion with the braided stents as compared to the laser cut stents. In fact, they also established that the flow diverter effect of a single braided stent was more than that achieved with the overlapping laser cut stents. In a series where a braided device was used as the primary stent, only one aneurysm recanalisation was noted and it needed retreatment. However, the drawback was that the radial force of these stents is lower as compared to that of a laser cut stent. It has been theorized that the radial force allows for tacking down of the intimal flap and straightening of the arterial segment, both of which play a stellar role in aneurysmal occlusion.,
Flow diversion appears promising as there is growing evidence that side branch occlusion is less of a concern. Outcomes appear favorable with this technique, with the peri-procedural ischemic complication rate and the retreatment rate being 8.3% and 2%, respectively. Two principles are to be followed in actual practice that allow for a lower periprocedural morbidity:First, a single device that is apposed to the wall serves better than multiple overlapping devices to avoid the endovascular leak and achieve a better long term occlusion rate; and second, the shortest device that ensures adequate coverage in order to avoid side branch occlusion as well as thromboembolism is recommended. Another technical aspect of note is to avoid overlapping the entry site of the contralateral vertebral artery, whereever possible, while deploying a flow diverter device [Figure 3].
|Figure 3: (a and b) A 43-year old male patient presented with mass effect from a fusiform partly thrombosed V4 segment aneurysm of the left vertebral artery (Note the entry point of the right vertebral artery). (c) A flow diverter (FRED) deployed across the aneurysm (Note: The flow diversion segment ends just proximal to the entry of the right vertebral artery). (d and e) Complete reconstruction of the V4 segment of the left vertebral artery|
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Reconstructive techniques necessitate administration of dual antiplatelet agents. In patients with a ruptured aneurysm, it is important to determine the need for inserting an external ventricular drain prior to loading them with antiplatelet therapy. The antiplatelet loading strategy appears to be varied. The authors have suggested loading with either clopidogrel or prasugrel; however, the dosing and the timing of administration needs further discussion. The effect of clopidogrel (4 to 8 hours) occurs at a later time point as compared to that of prasugrel (2 hours). Therefore, one may have to time the procedure in such a way that the stent delivery is planned at the time when the maximum effect of the drug is likely to occur. The optimal loading dose of clopidogrel appears to be 600 mg and that of prasugrel, 60 mg.
In conclusion, both endovascular trapping and reconstructive techniques appear to be good options for treating ruptured vertebral artery dissecting aneurysms. Parent artery occlusion is our preferred technique in patients with ruptured aneurysms, provided the other vertebral aretery is of a good size and the PICA is not arising from the aneurysmal segment. Other options include stent assisted coiling or flow diversion. Flow diverter technology appears promising in dissecting aneurysms particularly with the growing evidence in favor of this technique. Flow diverters can be considered as an option for un-ruptured aneurysms, and in cases in whom parent vessel occlusion is not possible.
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[Figure 1], [Figure 2], [Figure 3]