Mechanical thrombectomy for registrars

Why this matters

Mechanical thrombectomy is the standard of care for appropriately selected patients with acute ischaemic stroke from large vessel occlusion, and one of the most effective interventions in modern medicine for reducing disability. Success depends on rapid identification, accurate imaging interpretation, efficient workflow, careful procedural planning and thorough post-procedural care — and a registrar on the service touches most of those.

Time, and what must be documented

Time remains the strongest determinant of outcome. Every delay in the pathway costs tissue. These are the benchmarks the manual works to:

Documenting the times is a registrar job and it matters more than it feels like at 3am — the audit, the outcome analysis and any later review all depend on it.

• Last known well, and symptom discovery time
• Hospital arrival
• CT completion, and CTA completion
• Stroke activation
• Decision for thrombectomy
• Groin puncture
• First pass, and recanalisation
• Procedure completion

Clinical evaluation

Baseline functional status is established before treatment decisions are made, using the modified Rankin Scale. Patients who were independent, minimally disabled or of good premorbid quality of life derive the greatest benefit from reperfusion. The assessment is simply whether the patient was fully independent, needed assistance, or was bedbound or severely disabled.

A focused history identifies conditions that change the decision — previous stroke, hypertension, diabetes, atrial fibrillation, coronary artery disease, heart failure, chronic kidney disease and previous intracranial haemorrhage. Anticoagulant use needs particular attention: warfarin, apixaban, rivaroxaban, dabigatran and edoxaban, and for each, the last dose taken, the prescribed dose and compliance.

The NIHSS is the standard neurological assessment — level of consciousness, eye movements and gaze deviation, visual fields, facial weakness, motor function, sensory deficits, language, dysarthria and neglect. Record it on presentation, before transfer, immediately before thrombectomy, and after reperfusion. Serial scores are what make progression and response objective.

Imaging

The first objective of CT is exclusion of haemorrhage — intraparenchymal, subarachnoid and subdural. Early ischaemic change is then scored with ASPECTS, a 10-point system estimating infarct burden in the middle cerebral artery territory. Ten is normal; zero is complete MCA territory infarction. Higher scores generally mean more salvageable tissue and a better likelihood of benefit. The manual uses an ASPECTS of 7 or more for thrombectomy.

CTA identifies the site and side of occlusion, the extent of disease and the collateral circulation. Common thrombectomy targets are the internal carotid artery terminus, the M1 segment of the MCA, selected M2 occlusions, and basilar artery occlusions.

DWI–FLAIR mismatch

Used where onset is unknown or the stroke was discovered on waking. A positive mismatch — DWI hyperintensity present without corresponding FLAIR hyperintensity — suggests onset within approximately 4.5 hours and may support eligibility for reperfusion therapy.

Core and penumbra on CT perfusion

Perfusion imaging separates irreversibly infarcted tissue (core, CBF under 30%) from potentially salvageable brain (penumbra, Tmax over 6 seconds). Favourable candidates typically show a core volume under 70 mL, a mismatch ratio above 1.8, and an absolute mismatch above 15 mL.

Selection always integrates imaging with the clinical picture. Appropriate candidates generally show a confirmed large vessel occlusion, a disabling neurological deficit, reasonable premorbid function, no intracranial haemorrhage, and salvageable brain tissue.

Preparation

Laboratory testing should never delay treatment but should be obtained urgently: full blood count, urea and electrolytes, creatinine, INR, PTT and random glucose, with grouping and cross-matching where clinically indicated.

• Keep the patient nil per mouth to reduce aspiration risk.
• Two large-bore intravenous cannulas — 16G or 18G.
• Continuous ECG, pulse oximetry and blood pressure monitoring.
• Supplemental oxygen only when saturation falls below 94%.

On blood pressure: before reperfusion, patients receiving thrombolysis are maintained below 185/110 mmHg, while those not receiving thrombolysis may tolerate systolic pressure up to 220 mmHg. Aggressive lowering is avoided because cerebral perfusion may depend on the elevated systemic pressure. Labetalol and nicardipine are the agents in common use.

Communicate with anaesthesia early. General anaesthesia may be preferred where there is airway compromise, severe agitation, inability to lie flat, basilar artery occlusion or respiratory failure. Factors suggesting a difficult airway include obesity, facial trauma, a beard, reduced consciousness and active vomiting.

Technique

Aspiration thrombectomy

A large-bore aspiration catheter is advanced directly to the thrombus and negative pressure applied to extract it. Simple, quick to deploy, and capable of an excellent first-pass result.

Stent retriever thrombectomy

A stent retriever is deployed through the thrombus and withdrawn, trapping the clot in the stent struts. Effective against resistant thrombi and strong in fibrin-rich clot.

Combined technique

Aspiration and stent retriever used together, increasingly common, to maximise reperfusion rates and first-pass success.

Thrombus composition influences which approach works. Red-cell-rich thrombi are commonly associated with cardio-embolic stroke and atrial fibrillation — look for the hyperdense artery sign, or the susceptibility vessel sign on MRI — and respond well to aspiration. Fibrin-rich thrombi are associated with atherosclerotic disease and tandem lesions, and often respond well to stent retriever strategies.

Grading reperfusion

Reperfusion is assessed on the Thrombolysis in Cerebral Infarction scale. Modern procedural targets are TICI 2C or TICI 3.

Peri-procedural care

Fluid goals are euvolaemia, normotension and organ perfusion. Avoid hypotonic fluids, fluid overload and dehydration. Normal saline remains the most commonly used maintenance fluid. Patients with chronic kidney disease, diabetes or advanced age need particular attention to hydration and contrast minimisation.

Continuous heparinised flush systems maintain catheter patency, reduce intraluminal thrombosis and prevent stagnation within guide catheters. Practice varies significantly between centres and local protocol always governs. The manual gives one example preparation for teaching purposes only — 1,000 IU of heparin in one litre of 0.9% normal saline.

• Confirm the prescribed flush solution with the operator and nursing staff.
• Verify the pressure bags are functioning.
• Monitor ACT values when asked.
• Document every anticoagulant given, the ACT values, and the intraprocedural anticoagulation plan.

After the procedure

A structured handover covers three things: neurological status, with NIHSS before and after; procedural detail — access site, number of passes, devices used, complications and the final TICI score; and ongoing management — blood pressure targets, antithrombotic strategy and the follow-up imaging schedule.

• Symptomatic intracranial haemorrhage
• Vessel perforation
• Arterial dissection
• Embolisation to new territory
• Access-site complications
• Contrast reactions
• Reperfusion injury and hyperperfusion syndrome
• Stroke progression
• Death

Early recognition and prompt management of these are essential, and are consultant-led.

What every trainee on the service should be comfortable with

Imaging

ASPECTS scoring; CT perfusion interpretation; core versus penumbra; DWI–FLAIR mismatch; collateral assessment.

Procedural

Aspiration thrombectomy; stent retriever thrombectomy; combined techniques; balloon guide catheters; the first-pass effect.

Post-procedural

TICI grading; blood pressure targets; reperfusion injury and hyperperfusion syndrome; timing of antithrombotic therapy; symptomatic intracranial haemorrhage.

Mastery of these concepts is the foundation for safe participation in an acute stroke service. The companion checklist turns them into something you can work through on the day.