Keywords
acute ischemic stroke - mechanical thrombectomy - recurrent occlusion - stent clot
retriever
Introduction
Mechanical thrombectomy for acute ischemic stroke has been widely used since its efficacy
was proved.[1] During the procedure, a physician guides a microcatheter into vessels not visible
on fluoroscopy. In our patient with internal carotid artery (ICA) occlusion, we thought
that the distal tip of the stent retriever was deployed in the first segment of the
middle cerebral artery (MCA); however, the tip was in the narrow superior branch of
the second segment (M2) that originated straight from the first segment (M1). As a
result, repeated occlusion occurred, most likely due to endoluminal injury. The case
shows one possible cause of endoluminal damage, and the management of patients is
discussed to prevent periprocedural repeated occlusion.
Case History
A 74-year-old man was admitted to our emergency department with left-sided hemiplegia
80 min after onset. At admission, his National Institute of Health Stroke Scale score
was 13.[2] The 12-lead electrocardiogram revealed atrial fibrillation. Emergency diffusion-weighted
imaging demonstrated an area with partial high-signal intensity in the right cerebral
hemisphere. Magnetic resonance (MR) angiography showed occlusion of the right ICA.
The Alberta Stroke Program Early Computed Tomography score was 6.[3] Intravenous recombinant tissue plasminogen activator (rt-PA) injection was initiated
40 min after his arrival. He was transferred into the angiography room for endovascular
thrombectomy without confirming the efficacy of the rt-PA.
Under local anesthesia, a balloon guiding catheter (9-F Optimo; Tokai Medical Products,
Aichi, Japan) was advanced into the right ICA through the right common femoral artery.
Right carotid angiogram revealed total occlusion of the ICA ([Fig. 1A]). We attempted to recanalize via A Stent-retrieving into an Aspiration catheter
with Proximal balloon technique.[4] An aspiration catheter (REACT 71; Medtronic, Minneapolis, Minnesota, United States),
a microcatheter (Phenom 27; Medtronic), and a micro-guidewire (Eiger 14 FUMA; Medical
Innovation Co., Ltd., Tokyo, Japan) were coaxially navigated. After the microcatheter
was navigated into the distal portion of the horizontal segment of the MCA ([Fig. 1B and C]), a 6 × 40 stent clot retriever (Solitaire; Medtronic) was deployed and withdrawn
into the aspiration catheter, which was placed at the distal portion of the ICA ([Fig. 1D]). Some pieces of clot were confirmed to be attached to both the stent and aspiration
pump. Complete recanalization was achieved; however, we found that the stent retriever
had been deployed in a narrower branch in the M2 than expected ([Fig. 1E]). His symptoms immediately improved. An MR angiogram taken 8 hours after the procedure
demonstrated the patency of the ICA and MCA ([Fig. 1F]). Anticoagulation therapy with systemic heparinization was initiated 24 hours after
the administration of rt-PA.
Fig. 1 Radiological images of the initial procedure. (A) Initial right carotid angiography showing internal carotid artery occlusion. R indicates
the right-side. (B) Intraoperative X-ray image. Arrow indicates the tip of the microwire. The arrowhead
indicates the tip of the microcatheter. (C) Selective angiography showing the distal artery. (D) Arrowhead indicates the tip of the deployed stent. (E) Postoperative angiography showing recanalization. Arrow indicates the narrow branch.
(F) Magnetic resonance angiogram taken 8 hours after the procedure showing the patency
of the branch (arrow).
Thirty-two hours after the procedure, the patient again showed left hemiplegia. Emergency
angiography revealed a right M1 occlusion ([Fig. 2A]). We performed mechanical thrombectomy using the same system as the first procedure.
The microcatheter was advanced into the superior branch of the M2 ([Fig. 2B]). A Solitaire 4 × 40 stent clot retriever was used. A few clots were confirmed to
be attached to both the stent and aspiration pump. Although recanalization was achieved,
we confirmed an irregular inner surface and thrombus formation in the M2 ([Fig. 2C]). We decided to wait and observe for 10-minute in the angiography room. Then, repeat
angiography showed an M2 occlusion ([Fig. 3A]). We performed another thrombectomy using the same devices. A tiny clot was confirmed
to be attached to the stent. Recanalization was achieved, but the irregularity and
thrombus formation in the M2 remained ([Fig. 3B]). As a result, the thrombus was retrieved by the repeat stent retrieving, and it
was determined that the cause of the occlusion was thrombus, not dissection. There
were no findings of stenosis and dilation as in typical arterial dissection. The patient's
hemiplegia improved.
Fig. 2 Angiography images of the second procedure. (A) Right carotid angiogram showing middle cerebral artery occlusion (arrow). R indicates
the right-side. (B) Selective angiography showing the distal artery. Arrowhead indicates the tip of
the microcatheter. (C) Postprocedural angiography showing the recanalized branch (arrow).
Fig. 3 Radiological images of the third procedure and follow-up. (A) Right carotid angiography showing the superior branch of the second segment of the
middle cerebral artery (arrow). (B) After stent retrieval, the occlusion was recanalized (arrow). (C) Magnetic resonance (MR) angiography showing the patency of the recanalized branch
(arrow). (D) MR image showing no extension of the infarction.
Just after the procedure, antiplatelet therapy (cilostazol) was added. MR images taken
5 days after the second and third procedures showed the patency of the right M2 and
no extension of the infarction ([Fig. 3C and D]).
Discussion
Endovascular thrombectomy in patients with acute ischemic stroke is different from
other endovascular operations because of a lack of preprocedural anatomic information.
Moreover, a microcatheter must be navigated into a nonvisible, small, and fragile
intracranial artery upon fluoroscopy to use a stent clot retriever. The incidence
of perioperative complications during endovascular thrombectomy has been estimated
to be more than 10%, including arterial perforation (0.9–4.9%), arterial dissection
(0.6–3.9%), and vasospasm (3.9–23%).[5]
[6]
[7] Some authors have mentioned that minimizing the radial force of stent clot retrievers
or friction force against vessel walls may reduce the incidence of complications related
to such vessel injuries.[8]
[9]
[10]
In our case, we thought that the stent clot retriever had been deployed in the horizontal
part of M1 during the initial procedure, because the pigtailed-tip micro-guidewire
had been smoothly passed through. However, [Fig. 1D] shows that the distal markers of the Solitaire stent clot retriever do not appear
adequately dilated. When this finding is observed, the deployed stent should be withdrawn
in an extremely slow manner to prevent vessel injury. Moreover, we regret our strategy
of using a stent clot retriever in the second thrombectomy of the M1 occlusion. Direct
clot aspiration using an aspirator would have been better and gentler for the narrow
branch. As a result of the subsequent stent retrieval, repeated occlusion may have
been encouraged.
How do we recognize the size of a nonvisible artery during endovascular thrombectomy?
One way is to refer to the contralateral anatomical condition. However, as [Fig. 1F] shows, the left and right MCA anatomy are entirely different. Visually, the right
M1 is much shorter than the left M1. Microcatheter-withdrawing angiography can help
identify the actual crab claw sign, which indicates the precise position of a clot.[11] It may also identify the size of the nonvisible artery. However, as the authors
mention, microcatheter-withdrawing angiography requires penetrating the clot at least
twice with the tip of the microcatheter. This may result in clot distal migration
or separation.
For postoperative management, we added an antiplatelet over the anticoagulant after
the last procedure. The patient has not experienced another occlusion. Therefore,
the additional antiplatelet therapy may be effective in preventing thrombosis for
the narrow, damaged artery.
We report a case in which the cause of repeated MCA occlusion is thought to be endoluminal
injury due to the initial stent clot retrieval. Physicians should be aware of the
risk of endoluminal injury due to a stent clot retriever, especially when using a
large-sized stent against small branches. When there is the possibility of endoluminal
injury, adding antiplatelet therapy may be effective in preventing further thrombosis.
