mechanical thrombectomy

Radiopaedia • CC-by-nc-sa 3.0 • de

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

History

Despite a number of earlier trials, 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 .  As a result of these trials, endovascular clot retrieval has now become the standard of care for acute strokes.

Patient selection

  • acute ischemic stroke due to large vessel occlusion in the anterior circulation within 6 hours of symptom onset
  • several trials (e.g. DAWN and DEFUSE3 ) have shown that selected patient groups who fall outside the 6 hour time window also benefit from thrombectomy

Contraindications

  • 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...) 

Procedure

Preprocedural evaluation

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 .

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

Positioning/room set up
Equipment
  • stent retrievers
  • aspiration devices
  • balloon guiding catheter
  • microcatheters
Technique

Postprocedural care

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

Blood pressure control

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 .

If a 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 . 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.

Puncture site

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

Anticoagulation

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.

Complications

The overall complication rate is about 15% . Complications include :

Outcomes

The technical outcome is graded using the mTICI score. Thrombectomy is a highly effective treatment for stroke 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 .

Siehe auch: