Dipankar Dutta explains why NHS England specialised commissioning teams will be routinely funding and commissioning mechanical thrombectomy and what this might mean for patients and service provision
The aim of treatment in acute ischaemic stroke (AIS) is to clear the blocked artery and reperfuse the brain. Up until now this has been achieved by intravenous (IV) thrombolysis using alteplase, a tissue plasminogen activator (tPA). Over one‑third of ischaemic strokes are caused by large artery occlusion (LAO) and IV thrombolysis is often ineffective in this situation.
Mechanical thrombectomy is a recent breakthrough in the treatment of this type of stroke and has been shown to be more effective than IV thrombolysis. Mechanical thrombectomy is expected to become the standard of care soon.
Mechanical thrombectomy is expected to become the standard of care soon
At present there are several obstacles to the universal implementation of mechanical thrombectomy although national and international stroke guidelines and NICE have recognised mechanical thrombectomy as standard treatment.
NHS England has recently undertaken to routinely commission mechanical thrombectomy and in March 2018 it set out its policy position regarding commissioning mechanical thrombectomy for acute ischaemic stroke for all ages. The policy considers the current stroke pathway, immediate treatment, criteria, practices, and the impact of the full implementation of mechanical thrombectomy as part of the pathway for patients who comply with the criteria. It also defines NHS England’s commissioning position on mechanical thrombectomy as part of the treatment pathway for adults treated for severe ischaemic stroke where this is the responsibility of NHS England specialised commissioning teams.1
Procedure and setting
Mechanical thrombectomy can only be carried out in a tertiary stroke centre by a neurointerventionist, usually an interventional neuroradiologist (although other groups also perform this procedure). NHS England’s commissioning guidance stipulates that all thrombectomy centres must be recognised by NHS England as one of their listed centres for this procedure, meet their service specifications, and have regard to the British Association of Stroke Physicians (BASP) Standards for providing safe acute ischaemic stroke thrombectomy services.1,2 The BASP defines a suitable centre as a neuroscience centre incorporating hyperacute stroke units (HASU) embedded within a high‑quality comprehensive stroke service with access to neurosurgical, neurocritical care, and specialist stroke services.2 All centres must enter patients admitted with stroke on the Sentinel Stroke National Audit Programme (SSNAP) database, which is used to audit stroke treatment and outcomes.1
Most patients also have initial treatment with intravenous thrombolysis if they are within the time window (4.5 hours) and there are no contraindications.3
NICE interventional procedures guidance (IPG) 548 on Mechanical clot retrieval for treating acute ischaemic stroke4 summarises the procedure. It is usually done under sedation but general anaesthesia is often needed.2 Cerebral angiography is done to show the exact location of the arterial occlusion. A delivery catheter is inserted, usually through the femoral artery in the groin, and advanced into the occluded artery using X‑ray guidance. A clot‑retrieval device attached to a guidewire is introduced through the delivery catheter to the site of the occlusion, to remove the clot and re‑establish blood flow. The devices in current use are stent retriever devices sometimes with balloon guide catheters for flow occlusion (to reduce forward flow thereby reducing the chance of distal embolisation), direct aspiration catheters, or combined stent retrievers/aspiration catheters.3, 4 Acceptable standards are considered to be groin puncture time to start of revascularisation of <45 minutes in at least 65% of patients and end of revascularisation in a time of median ≤60 minutes.2
Patient selection is usually made jointly between stroke physicians and neurointerventionists.3 Depending on stroke service configurations in different regions, patients may present directly to a tertiary centre. This has been called the ‘mothership’ model and is clearly the most efficient pathway in ensuring timely treatment.3, 5 However, geographical constraints may make this impossible and patients may present initially to a peripheral centre where they are assessed and transferred to a tertiary centre while receiving IV tPa prior to thrombectomy. This has been called the ‘drip and ship’ model.3, 5 Communication between centres has to include telephone contact and viewing of images remotely via a picture archiving and communication system (PACS). The assessment has to be rapid but thorough and consists of stroke diagnosis, likely localisation, assessment of severity, pre‑stroke functional status, and co‑morbidities.3 The procedure remains very time‑dependent; for every 15 minutes saved in reperfusion, an estimated 39 patients per 1000 treated would be less disabled at 3 months, including 25 more who would achieve functional independence.6
Once the procedure is complete, the patient will need to be monitored in the hyperacute stroke unit (HASU) or neurocritical care (usually if they received a general anaesthetic) of the tertiary centre. Most will require repatriation to their parent hospitals for ongoing rehabilitation and some may be suitable for early discharge, usually with support from the early supported discharge team (ESDT).
… for every 15 minutes saved in reperfusion, an estimated 39 patients per 1000 treated would be less disabled at 3 months
The national stroke guideline 2016 concluded that mechanical thrombectomy is an effective acute treatment for selected patients with proximal large artery occlusions as an adjunct to IV thrombolysis, and a standalone treatment for those patients with contraindications to IV thrombolysis.7 Similarly, NICE has reviewed the evidence and issued guidance (IPG548) recommending mechanical thrombectomy.4
The overall complications rate of mechanical thrombectomy is about 15%, based on recent trial data.3 However, many complications are minor and do not affect final outcomes for patients.3
A recent systematic review of cost effectiveness reviewed data from 17 studies and concluded that mechanical thrombectomy was cost effective and good value for money with a threshold of $50,000 per Quality Adjusted life Year (QALY).8 NICE uses a threshold of £30,000 per QALY. Two UK studies using Markov modelling have suggested cost effectiveness; a 100% likelihood of cost‑effectiveness for a £30,000 threshold value and an incremental cost per QALY gained of mechanical thrombectomy over a 20‑year period of £7061.9,10 The cost of mechanical thrombectomy was estimated to be £8365 (including the cost of the stent retriever and the whole procedure) in the latter study.10
Given the complex and time‑dependent nature of mechanical thrombectomy, there are major challenges to the implementation of mechanical thrombectomy in the UK and other parts of the world. There are obvious geographical, organisational, and financial barriers to providing a round‑the‑clock service.11
The most significant problem is probably the lack of trained neurointerventionists; in 2017, there were about 80 such specialists in the UK and 24 neuroscience centres in England.12 There will be significant difficulties in training neurointerventionists and the British Society of Neuroradiologists (BSNR) has issued recommendations on training and suggested training numbers and competencies.13 It has been suggested that given appropriate training, other groups (general interventional radiologists, cardiologists, stroke physicians, or neurologists) may be able to support neurointerventionists.12 Numbers will have to be high enough to support 24/7 rotas covering 365 days a year. At present, at least one centre in the UK is running such a rota and other existing, within hours, services are in the process of expanding their coverage.
The most significant problem is probably the lack of trained neuro- interventionists
Where ‘drip and ship’ is the only possible model, staff such as radiographers (with the training to perform CT angiograms) in the receiving hospitals may be found to be in short supply and there may be capacity issues within local radiology services. Local specialists such as stroke physicians/neurologists are also in short supply and may find it difficult to cover 24/7 rotas for the assessment of acute strokes for thrombectomy. Rapid referral pathways and transport to the neuroscience centre will have to be established.
Funding and commissioning
There are approximately 80,000 stroke admissions in England per year.1 Currently, around 12% of all stroke patients receive IV thrombolysis and an estimated 8000 patients per year may be eligible for mechanical thrombectomy.1 Funding and commissioning of mechanical thrombectomy will be managed through the relevant local NHS England specialised commissioning team.1 Reimbursement for treatment will be dependent on activity being reported via the Secondary Uses Service (SUS) and is dependent on entering patient level data in the Sentinel Stroke National Audit Programme (SSNAP) database.1 The appendix to the NHS England document provides advice on coding for the intervention and indicates that the revenue cost per patient is based on HRG YA12Z with the cost of the device included in the tariff.1 According to the current National Tariff Workbook, the set reimbursement is a non‑elective spell tariff of £11,762.14
Mechanical thrombectomy is a new treatment modality for a subset of acute ischaemic strokes that has been proven to be very efficacious and cost effective. There are practical difficulties with its universal implementation which will gradually be overcome. An estimated 10% of strokes will benefit from this treatment but, as with any other stroke, high quality stroke unit care in the acute and rehabilitation phases is needed for good patient outcomes.
Editor’s note: For further clinical detail on mechanical thrombectomy, see the November issue of our sister publication, Guidelines in Practice, where Dr Dutta has written an article aimed at primary care clinicians and commissioners (www.guidelinesinpractice.co.uk).
1. NHS England Specialised Commissioning team. Clinical Commissioning Policy: mechanical thrombectomy for acute ischaemic stroke (all ages). NHS England, 2018. Available from: www.england.nhs.uk/publication/clinical-commissioning-policymechanical-thrombectomy-for-acuteischaemic-stroke-all-ages/
2. White P, Bhalla A, Dinsmore J et al. Standards for providing safe acute ischaemic stroke thrombectomy services (September 2015). Clin Radiol 2017; 72 (2): 175.e1–175.e9.
3. Evans M, White P, Cowley P, Werring D. Revolution in acute ischaemic stroke care: a practical guide to mechanical thrombectomy. Pract Neurol 2017; 17: 252–265.
4. NICE. Mechanical clot retrieval for treating acute ischaemic stroke. NICE Interventional Procedures Guideline 548. NICE, 2016. Available at: www.nice.org.uk/ipg548
5. Milne M, Holodinsky J, Hill M et al. Drip ’n ship versus Mothership for endovascular treatment: modeling the best transportation options for optimal outcomes. Stroke 2017; 48 (3): 791–794.
6. Saver J, Goyal M, van der Lugt A et al. Time to treatment with endovascular thrombectomy and outcomes from ischemic stroke: a meta-analysis. JAMA 2016; 316 (12): 1279–1288.
7. Bowen A, James M, Young G et al. National clinical guideline for stroke—fifth edition 2016. London: Royal College of Physicians, 2016. Available at: www.strokeaudit.org/SupportFiles/Documents/Guidelines/2016-National-Clinical-Guideline-for-Stroke-5t-(1).aspx
8. Sevick L, Ghali S, Hill M et al. Systematic review of the cost and cost-effectiveness of rapid endovascular therapy for acute ischemic stroke. Stroke 2017; 48 (9): 2519–2526.
9. Lobotesis K, Veltkamp R, Carpenter et al. Cost-effectiveness of stent-retriever thrombectomy in combination with IV t-PA compared with IV t-PA alone for acute ischemic stroke in the UK. J Med Econ 2016; 19 (8): 785–794.
10. Ganesalingam J, Pizzo E, Morris S et al. Costutility analysis of mechanical thrombectomy using stent retrievers in acute ischemic stroke. Stroke 2015; 46 (9): 2591–2598.
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13. Lenthall R, McConachie N, White P, Clifton A, Rowland-Hill C. BSNR training guidance for mechanical thrombectomy. Clin Radiol 2017; 72 (2): 175.e11–175.e18.
14. NHS Improvement. National tariff payment system 2017/18 and 2018/19 Annex A: The national prices and national tariff workbook, 1a APC & OPROC 17.18. Available at: improvement.nhs.uk/resources/nationaltariff-1719/#h2-annexes