Endovascular clot retrieval (ECR)

Last revised by Andrew Murphy on 28 Jun 2021

Endovascular clot retrieval (ECR) is increasingly performed in patients presenting with emergent large vessel occlusion (ELVO), especially those with a large ischemic penumbra that is likely to progress to ischemic stroke. To be successful, careful patient selection and dedicated training and equipment are necessary. 

Thrombectomy and its efficacy in ischemic stroke have been explored since 2005, however initial trials revealed disappointing results. This was attributed to an inability to confirm large vessel occlusions radiologically combined with insufficiently developed devices and treatment delays 18. It was only in 2015, that multiple randomized controlled trials showed improved clinical outcome in patients with acute stroke due to large vessel occlusion undergoing thrombectomy compared to medical (conservative) treatment alone 3-5. As a result of these trials, endovascular clot retrieval has now become the standard of care for large vessel occlusion strokes involving the anterior circulation. 

  • acute ischemic stroke due to large vessel occlusion in the anterior circulation within 6 hours of symptom onset
  • several trials (e.g. DAWN 13 and DEFUSE3 6) have shown that selected patient groups who fall outside the 6 hour time window also benefit from thrombectomy 12
  • acute ischemic stroke due to large vessel occlusion in the posterior circulation remains an area of uncertainty and selection is dependent on clinician judgment in accordance with local guidelines
  • intracranial hemorrhage on initial non-contrast CT
  • large infarct core with no significant penumbra (i.e. no salvageable brain)
  • various patient factors (e.g. pre-morbid functional status, advanced directives, etc...) 

Non-contrast enhanced CT is used to exclude hemorrhage and CT angiography to determine large vessel occlusion. Alternatively, MRI and DSA may also demonstrate the occlusion although this is less common due to difficulty with timely access to MRI in most institutions.

Angiographic imaging can also assess collateral vessels which contribute to predicting outcome in some settings 8.

The role of advanced imaging such as CT perfusion to determine the infarct core and penumbra size is still uncertain 10, yet the technique is being ushered into more and more centers based on international guidelines 11.

  • stent retrievers
  • aspiration devices
  • balloon guiding catheter
  • microcatheters

Although successful technical clot retrieval is essential, appropriate postprocedure care is also critical to avoid complications. 

Avoiding excessively high blood pressure is important in reducing the risk of secondary hemorrhage. In the acute post-thrombectomy/thrombolysis period a target BP <185/110 mmHg is recommended 14.

If critical carotid stenosis (tandem lesion) has been treated then more aggressive blood pressure control is probably warranted to avoid the possibility of cerebral hyperperfusion as well as hemorrhage 16. There are, however, few universally agreed-upon guidelines and chosen targets will vary according to pre-procedure blood pressure, anticoagulation, pre-ECR thrombolysis, size of the expected infarct and a variety of other factors. 

Groin site neurovascular observations and bed rest are required as usual. There is an increased move towards radial artery access for lower complication rates 17

In a variety of settings, anticoagulation may need to be restarted shortly after clot retrieval (e.g. antiplatelet agents for stenting, anticoagulation for atrial fibrillation). The timing of this is on a case by case balance and involves balancing the risk of thromboembolic complications from delaying anticoagulation versus the increased risk of a cerebral hemorrhage.

The overall complication rate is about 15% 1. Complications include 2,9:

The technical outcome is graded using the mTICI score. Thrombectomy is a highly effective treatment for strokes affecting the anterior circulation, with a number needed to treat (NTT) of 2.6 for an improved functional outcome. In a meta-analysis, 46% of patients treated with mechanical thrombectomy achieved functional independence (modified Rankin scale (mRS) 0–2 at 90 days) compared to 27% for best medical treatment 2. Outcomes in posterior circulation strokes remain mixed. One randomized controlled trial of basilar stroke patients found 44.2% of patients managed with mechanical thrombectomy achieving a 90-day modified Rankin scale of 0-3, in contrast to 37.7% in those receiving medical treatment with no statistically significant difference found between groups 19

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Cases and figures

  • Figure 1: ICA/M1 occlusion treated with mechanical thrombectomy
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  • Case 1: right MCA infarction with thrombectomy
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  • Case 2; proximal right MCA M1 segment embolic occlusion
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  • Case 3: acute left middle cerebral artery territory infarct with clot retrieval
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  • Case 4: basilar tip thrombus with endovascular clot retrieval
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  • Case 5: acute P1 occlusion treated with ECR
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