Research letter: An updated survey of intra-arterial mechanical thrombectomy service provision in England

Dear Professor Kennedy Lees,

Mechanical Thrombectomy (MT) is a highly effective treatment for large artery occlusive stroke ¹ but due to the specialist facilities and workforce required it is a ‘disruptive innovation’. ² In 2015 we surveyed the clinical leads of the 24 neuroscience centres providing MT across England to establish the baseline of existing thrombectomy services. The survey highlighted challenges in moving to 24/7 provision of MT, notably availability of neurointerventionist workforce and lack of agreed standards for triage and patient transfers. ³ Formal commissioning of MT by National Health Service (NHS) England occurred in 2017 but progress in MT implementation has been slow, ² further impacted by the Covid pandemic. ⁴ In 2021–2022, the UK Stroke National Sentinel Audit (SSNAP) reported a thrombectomy rate of 2.4%, ⁵ whereas the NHS England target was 10% by the end of 2022. We updated and repeated the 2015 survey to describe factors that might be responsible for slow implementation and key practice variations. The survey was conducted using Qualtrics XM™ data collection and analysis platform by links emailed to the clinical leads of the 23 active English thrombectomy centres in June 2021 (one centre at that time being inactive). Questions were based upon the prior 2015 survey ⁵ but expanded after consultation with stroke/neurointerventional clinicians.

All 23 active thrombectomy centres responded (June-December 2021). All thrombectomy providers now had a formal MT protocol (56% in 2015), 96% had a protocol for inter-hospital transfers (up from 33%). Median number of MT operators was 4 (previously 3). Four centres (17%) reported 24/7 MT provision (previously 1) but the distribution of 24/7 cover was geographically unequal with three of the centres in London. Eleven centres (48%) provided 7 day extended hours (up from 11%); four centres (17%) provided some lesser extended hours service. Six centres (26%) had a weekday hours only service (67% in 2015; when another 17% had no regular MT provision); two centres reported some delivery of MT by non-INRs (previously none). Overall, the survey reported 95 MT operators across England, an increase from 65 in 2015.

External referrals (19/23, 83%) were by referring stroke unit physicians (SP) to either MT centre SP (17) or neurointerventionist (2), other stroke practitioner (nurse or junior doctor) referred in 3 (13%) and any doctor referred in 1 (4%). Repatriation policy for transferred patients was after at least one overnight stay in 17 (74%) centres; ward admission and 12–24 h repatriation in three centres (13%) and repatriation within 12 h without ward admission in three. The proportion of centres with strict adherence to National Institute of Care and Health Excellence (NICE) Thrombectomy guidelines reduced from 50% in 2015 to 27%, indicating that patient selection increasingly reflects guideline interpretation for individual patients based upon growing experience, application of more recent study evidence and improved access to advanced imaging. Where services did not adhere strictly to commissioned or NICE guidance, most centres indicated they considered MT in broader populations rather than refusing to consider extra-guideline MT, as had been the case in 2015. Current MT selection criteria differed according to time of day in 3 (13%) centres. There was a slight change in anaesthetic technique since 2015 with an increase in general anaesthesia from 22% to 30%. However, the primary therapeutic strategy had changed markedly with reduction in stent-retriever alone (from 61% to 0%) and corresponding increase in both combined direct aspiration/stent-retriever techniques (0%–39%) and centres with no predefined primary technical strategy (from 34% to 44%).

National SSNAP data indicate local referring stroke units without MT capability should provide 74% of patients undergoing MT, yet the proportion of patients undergoing MT following transfer from a local (non-MT) stroke unit is <55%, resulting in thrombectomy rate for direct admissions to MT centres almost treble that for secondary transfers. ⁵ Therefore, optimising early identification of patients eligible for MT and expeditious transfer are key priorities to improve MT rates. Other recommendations to increase delivery of MT to levels of equivalent healthcare systems would relate to networking, workforce expansion in acute and comprehensive stroke centres (stroke physicians, specialist nurses, radiographers anaesthetists and neurointerventionists), second angiographic suite immediate availability and efficient rapid repatriation processes. More evidence is required about how best to identify eligible patients early and convey them quickly to MT centres.

In summary, despite clear development since 2015, there remains considerable variation in MT services across England including 24/7 provision, imaging and triage strategies and technical aspects of the procedure. Rapid progress is needed to match the performance of equivalent healthcare systems.