General Description

Mechanical thrombectomy has become a standard of care for large-vessel occlusion (LVO) with acute ischemic stroke (AIS). Numerous randomized trials have demonstrated the procedure’s efficacy and therapeutic benefit. The two techniques most widely used today include a direct first pass aspiration technique (ADAPT), which was discussed previously in Chapter 16, and stent retriever-based clot retrieval. This chapter will describe the stent-retriever technique. Stent retrievers are available in different sizes and from different manufacturers. Stent retrievers are deployable devices that can be retrieved via their pusher wire. They typically require a 21-gauge or larger catheter for delivery into a vessel. Some are fluoroscopically visible throughout their length (e.g., Trevo, Stryker and Solitaire Platinum, Medtronic). Others are visible only at the tip (Solitaire, Solitaire 2, or Solitaire 3, Medtronic). Stent retrievers yield high recanalization rates in LVO and can be utilized alone, with aspiration, or as a rescue therapy for aspiration-based techniques. Stent retrievers come in a range of sizes from 4 mm to 6 mm × 20 mm and 40 mm. Vessel perforation and reperfusion hemorrhage are the two main concerns related to stent-retriever mechanical thrombectomy. Patient selection can help minimize risk.

Indications

Mechanical thrombectomy is indicated in AIS because of LVO (occlusion of the internal carotid artery [ICA] or middle cerebral artery [MCA] branches [M1, M2, M3, and/or M4]) resulting in a National Institutes of Health Stroke Scale (NIHSS) score > 6. Intervention should be carried out within 6 hours of symptoms or if perfusion imaging reveals a large penumbra with little or no ischemic core. We prefer that the patient also has computed tomographic angiography of the head and neck vessels to avoid the discovery of other anomalies during the intervention (i.e., tandem occlusions or ostial stenosis).

Neuroendovascular Anatomy

The ICA normally originates from the common carotid artery (CCA) at the C3-4 or C4-5 vertebral level; it may occur as low as T2 and as high as C1. The petrous portion of the ICA runs forward and medial to the area of the foramen lacerum, where it moves superiorly into the cavernous sinus and creates a siphon upon itself before exiting at the distal dural ring. The first branch beyond the distal ring (subarachnoid) is typically the ophthalmic artery, followed by the communicating segment of the vessel. The ICA bifurcates into the A1 (first anterior cerebral artery segment) and M1 segment of the MCA. The M1 (4–5 mm diameter) segment can have accessory and duplicated branches. Perforators going to the basal ganglia (i.e., lenticulostriate arteries) arise from the superior surface of the M1, and care should be taken to avoid inadvertent selection of these with the microwire. The MCA bifurcates (sometimes trifurcates) again near the bottom of the sylvian fissure (this can be variable), and an inferior branch courses to the M3 and M4 segments over the temporoparietal region. The superior M2 division moves frontally supplying the M3 and M4 vessels to Broca’s area as well as the motor area. Vessels in patients with AIS can have severe intracranial atherosclerotic disease (ICAD). Thrombus can form at these sites as well. Furthermore, some patients can become symptomatic from ICAD stenosis because of hypoperfusion and the symptoms can mirror AIS; however, in this situation, thrombectomy is typically not needed. Surgical or endovascular revascularization with angioplasty or bypass is necessary in this case.

Periprocedural Medications

Stent-retriever mechanical thrombectomy procedures are usually performed with the patient awake and under little or no sedation. Typically, the patient has received intravenous tissue plasminogen activator (t-PA), thus, further anticoagulation or antiplatelet therapy is contraindicated. If permanent stent placement is necessary, a loading dose of aspirin and clopidogrel can be administered.

Specific Technique and Key Steps

1. 
   

   Most centers require specific times to be recorded for groin access, initial digital subtraction angiography (DSA) runs, microcatheter and device deployment times, and final recanalization times.

   
   
2. 
   

   We begin by assembling all of the necessary catheters on the back table and connecting them to heparinized flushes. We lay them out on the angiogram table. The stent-retriever device is selected after reviewing the initial images so the appropriate diameter and length of the device can be determined, depending on the size and location of the clot.

   
   
3. 
   

   Access is obtained via a femoral arteriotomy made with a micropuncture set. A 6 French (F) or an 8F guide sheath is placed. If an 8F sheath is used, a transitional 6F dilator is utilized once the microwire is deemed appropriate in relation to the femoral head seen on fluoroscopy. Then, the 8F sheath is placed.

   
   
4. 
   

   The guide sheath (90 cm) with copilot valve is placed over an intermediate diagnostic catheter (e.g., VTK 125 cm, Cook Medical) and then over a Glide Advantage 180-cm wire (Terumo) and advanced into the CCA.

   
   
5. 
   

   Subtracted runs are taken from the CCA prior to advancing the guide catheter into the ICA (if large enough) under roadmap guidance ( Fig. 18.1–18.11, Video 18.1–18.11 ).

   
   
6. 
   

   Intracranial anteroposterior and lateral runs are performed, and the site of occlusion is identified.

   
   
7. 
   

   The assembled intermediate large-bore aspiration catheter and the microcatheter and microwire combination are then inserted into the guide catheter. Under fluoroscopy, the microwire and microcatheter, followed by the intermediate catheter, are advanced to (but not past) the occlusion site, taking care to account for any built-up tension in the system while nearing the thrombus. Some angiographers cross the lesion with a microwire under suction from the intermediate catheter. In any case, the lesion must be crossed with the microwire and microcatheter. The microwire can then be withdrawn and a microinjection performed to ensure that the vasculature distal to the occlusion is patent ( Video 18.1–18.11 ).

   
   
8. 
   

   The stent-retriever device is then appropriately sized for the vessel. Typically, a 4-mm device is sufficient for M1 and beyond. Larger devices can be selected for larger clots.

   
   
9. 
   

   The device is pushed into the rotating hemostatic valve and back flushed. Then, it is loaded into the microcatheter. Fluoroscopy should be utilized to push the device beyond the fluoro-save. The catheter is pinned at the hub, and the device is pushed to the end of the catheter and beyond the clot. The ideal landing zone for the retriever is to have the clot at its mid to proximal area ( Fig. 18.1–18.11, Video 18.1–18.11 ).

   
   
10. 
    

    The stent retriever is deployed by holding the device wire and removing the microcatheter. This maneuver has to be performed carefully and might involve a learning curve. The goal is to keep the device in place while the microcatheter is removed. After 3 minutes of deployment, some angiographers perform microinjections to assess for recanalization. The microcatheter is removed, now pinning the stent. The intermediate large-bore aspiration catheter is turned to suction after 3–5 minutes, and the stent retriever is slowly withdrawn into the intermediate catheter ( Video 18.1–18.11 ).

    
    
11. 
    

    The stent retriever is inspected for clot. Final runs are obtained to determine whether contrast extravasation is present, indicating that another pass with the retriever is needed. The intermediate catheter is also withdrawn under suction and inspected for clot. The guide catheter should be aspirated with two large 30-mL syringes.

    
    
12. 
    

    The microwire/microcatheter is reassembled within the aspiration catheter in the event that another pass is needed.

    
    
13. 
    

    Post-thrombectomy DSA runs are performed. If the clot has been removed and a thrombolysis in cerebral infarction (TICI) grade of 2b or 3 is achieved, the procedure is done, and the patient’s neurologic status should be checked. If the clot persists, consideration is given to making another pass ( Video 18.1–18.11 ).

    
    
14. 
    

    CCA runs are performed after the removal of the guide catheter. A groin run is also performed, if not already completed, to determine eligibility for a closure device (e.g., AngioSeal, Terumo).

    
    
15. 
    

    If the patient is stable and more information on collateral supply is needed, a full diagnostic angiogram can be completed.

Device Selection

In our practice, the following are the common set-ups and devices used for stent-retriever mechanical thrombectomy:

• 
  

  21-gauge micropuncture set, Cope Mandril wire (Cook Medical), 6F or 8F sheath, 6F dilator.

  
  
• 
  

  Guide catheter (e.g., Neuron MAX, Penumbra or Flexor Shuttle, Cook Medical).

  
  
• 
  

  Intermediate diagnostic catheter (e.g., VTK 125 cm 5F catheter).

  
  
• 
  

  Glide Advantage 0.035-inch wire 180 cm.

  
  
• 
  

  Large-bore aspiration catheter (Sofia or Sofia Plus, MicroVention).

  
  
• 
  

  0.027-inch microcatheter (e.g., Velocity, Penumbra; Headway, MicroVention; Marksman, Medtronic).

  
  
• 
  

  0.014-inch microwire (e.g., Synchro 2 Standard or soft wire, Stryker).

  
  
• 
  

  Suction tubing or large syringe.

  
  
• 
  

  Continuous heparinized saline flush.

  
  
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  Stent-retriever device (e.g., Trevo or Solitaire).

Pearls

• 
  

  The most difficult part of the initial process can be delivering the guide catheter into the CCA in tortuous anatomy ( Fig. 18.5, 18.7, Video 18.5, 18.7 ). After a CCA run, the 0.035-inch or 0.038-inch wire can be looped into the external carotid artery for extra purchase.

  
  
• 
  

  When navigating past a thrombus, use caution and knowledge of anatomy to ensure that you stay within a vessel even though it may not fill on subtracted images. Native issues can also be useful. This will help avoid perforations.

  
  
• 
  

  A gentle “J” curve is needed on the microwire to allow navigation of the cerebral vessels and avoid vessel perforation.

  
  
• 
  

  Beware of dissections that can masquerade as thrombus. Microinjections can help discern the thrombus from dissections. The skull base and distal dual ring are common locations for dissections.

  
  
• 
  

  Always beware of reperfusion hemorrhage; monitor angiographic runs for contrast extravasation and stagnation.

  
  
• 
  

  Balloon guide catheters (BGCs) can be used (e.g., Cello, ev3); however, they can be very stiff and require a larger sheath (9F). Some large-bore aspiration catheters will not fit within the BGC ( Fig. 18.2, 18.3, Video 18.2, 18.3 ).

  
  
• 
  

  Distal clot migration is possible with ADAPT as well as stent retriever techniques. If concerned, perform a run. If a smaller vessel is blocked distally, a smaller aspiration catheter can be utilized.

  
  
• 
  

  If tandem occlusions are identified and carotid stenting is needed, we prefer to stent the carotid artery and then treat the intracranial thrombus during the same procedure (see Chapter 20). The guide catheter can be advanced past the stent if possible prior to stent retriever thrombectomy to avoid disturbing the newly placed carotid stent.

  
  
• 
  

  Beyond the M2 vessels, the risk-versus-benefit ratio starts to become unfavorable for intervention. If the initial NIHSS score was > 6 and no LVO was found on the angiogram, it is likely that the t-PA broke up the clot.

  
  
• 
  

  As mentioned, reperfusion hemorrhage and vessel perforation are the two main concerns associated with stent-retriever mechanical thrombectomy. If a BGC is being used, it can be inflated temporarily to treat reperfusion hemorrhage. If perforation is encountered on microinjection prior to clot removal, resheath the device and allow the thrombus to palliate the hemorrhage.

Case Overview: CASE 18.1 Acute Middle Cerebral Artery Occlusion: Solumbra Technique

• 
  

  A 75-year-old female presented to the emergency department at 7 a.m. with acute onset of left-sided weakness and abnormal speech. She was seen normal the night before (wake-up stroke). Neurological examination demonstrated severe left right hemiparesia, dysarthria, and left side neglect. Her initial National Institutes of Health Stroke Scale score (NIHSS) was 11. She has a past medical history of hypertension, chronic heart failure, and pancreatic cancer. Patient did not receive intravenous tissue plasminogen activator (tPA).

  
  
• 
  

  Computed tomography (CT) was normal. CT angiography demonstrated right middle cerebral artery (MCA) occlusion. CT perfusion demonstrated increased time-to-peak with a large area of preserved volume on the right hemisphere.

Tips, Tricks & Complication Avoidance

• 
  

  It is important to have a large guide catheter in the cervical internal carotid artery (ICA) to easily accommodate a 6F aspiration catheter. The guide catheter can be a balloon guide catheter.

  
  
• 
  

  The Solumbra technique requires a three-axial system (large bore aspiration catheter, microcatheter (0.027-inch and microwire). Assemble and advance them all together as a unit until the thrombus is reached.

  
  
• 
  

  If the large bore aspiration catheter gets caught in the ophthalmic artery, keep advancing the microcatheter and microwire further until the thrombus is crossed. Once the stent retriever is advanced, it can be used as extra support for the reperfusion catheter to cross the ophthalmic ICA segment.

  
  
• 
  

  Do a gentle contrast injection when performing the angiography run to avoid vessel perforation.

  
  
• 
  

  If the vessel remains occluded after the first attempt, confirm thrombus length and adequate coverage, try a larger aspiration catheter, and advance the aspiration catheter further distally over the stent retriever.

Case Overview: CASE 18.2 Acute Internal Carotid Artery Bifurcation Occlusion: Solumbra technique with balloon guide catheter

• 
  

  A 61-year-old female presented to the emergency department with acute onset of left-sided weakness. She was seen normal 12–13 h prior to her arrival. On neurological examination she was awake, confused, with dysarthria, left hemianopsia, left hemiparesia, left facial palsy, and left-side neglect. Her initial National Institutes of Health Stroke Scale score (NIHSS) was 18. She has a past medical history of diabetes, chronic heart failure, and atrial fibrillation. Her medications included aspirin, coumadin, and metformin. Patient was out of the window for intravenous tissue plasminogen activator (tPA) administration.

  
  
• 
  

  Computed tomography (CT) was normal. CT angiography demonstrated right internal carotid artery (ICA) bifurcation occlusion. CT perfusion demonstrated increased time-to-peak with preserved volume on right hemisphere.

Tips, Tricks & Complication Avoidance

• 
  

  Advance the balloon guide catheter into the cervical ICA as distal as possible.

  
  
• 
  

  Inflate and deflate the balloon to check patency and adequate artery occlusion. Do not overinflate the balloon as this could dissect the artery.

  
  
• 
  

  Do not inflate the balloon until you are ready to cross the thrombus and deploy the stent retriever.

  
  
• 
  

  On the post-thrombectomy angiography run, pay attention to the MCA and ACA territories and look for possible distal thrombus fragmentation. It is not uncommon to focus only on the MCA territory and miss distal ACA occlusions.

  
  
• 
  

  If revascularization is not achieved with one pass, the process can be repeated with the same device 3–5 times using the same steps.

  
  
• 
  

  Special attention should be paid to clean the aspiration catheter and the stent from any thrombus/debris before reusing.

Case Overview: CASE 18.3 Acute Internal Carotid Artery Terminus Occlusion: Balloon Guide Catheter

• 
  

  A 71-year-old female presented to the emergency department after loss of consciousness, right-sided weakness, and inability to speak. She was seen normal 2 h prior to her arrival. On neurological examination, she was somnolent, confused, not following commands, with right hemiparesis, left gaze deviation, right facial palsy, and right-side neglect. Her initial National Institutes of Health Stroke Scale score (NIHSS) was 19. She has a past medical history of hypertension, chronic heart failure, and atrial fibrillation. The patient was taking coumadin but discontinued it 4 months prior for unknown reasons. Patient received tissue plasminogen activator (tPA) with minimal improvement.

  
  
• 
  

  Computed tomography (CT) was normal. CT angiography demonstrated left internal carotid artery (ICA) bifurcation occlusion. CT perfusion demonstrated increased time-to-peak with preserved volume on left hemisphere, prominently on a distal middle cerebral artery (MCA) branch.

Related posts:

17 Anterior Circulation Aspiration-Only Mechanical Thrombectomy (ADAPT) 20 Mechanical Thrombectomy with Intracranial Stenting/Angioplasty 21 Anterior Circulation Mechanical Thrombectomy with Extracranial Stenting/Angioplasty 22 Intracranial Atherosclerotic Disease—Intracranial Angioplasty 19 Posterior Circulation Mechanical Thrombectomy 29 Aneurysm Embolization with Liquid Embolic Agents

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