Key Findings (Advice 2018)
A meta-analysis of eight RCTs (n=1,841) found that patients with ischaemic stroke treated with mechanical thrombectomy plus standard care were significantly more likely to be functionally independent at 90 days compared with patients treated with standard care alone: odds ratio (OR) 2.07, 95% confidence interval (CI) 1.70 to 2.51, p<0.00001. There were no statistically significant differences in 90-day mortality or symptomatic intracranial haemorrhage (ICH).
In a meta-analysis of four RCTs (n=518), patients with ischaemic stroke treated with mechanical thrombectomy plus standard care a median of 10.8 hours after they were last known to be well, had significantly better odds of functional independence at 90 days compared with patients treated with standard care alone: OR 3.33, 95% CI 1.81 to 6.12, p<0.0001. Patients in two of the included RCTs had been selected using advanced imaging.
A network meta-analysis found no statistically significant differences in functional independence at 90 days or symptomatic ICH in comparisons between mechanical thrombectomy devices (Trevo®, Solitaire™ aspiration) and between thrombectomy strategies (stent retriever or aspiration) for treatment of patients with ischaemic stroke.
In a systematic review of eight economic evaluations mechanical thrombectomy using stent retriever devices was cost effective or dominant (less expensive and more effective) compared with standard medical care for treatment of ischaemic stroke.
In a meta-analysis of eight studies (one RCT and seven retrospective cohorts, total n=2,068) the mean times from symptom onset to thrombolysis, puncture, and reperfusion for ischaemic stroke patients treated with mechanical thrombectomy were significantly shorter in a ‘mothership’ compared with a ‘drip and ship’ model of care. The mothership model was associated with a significantly higher rate of functional independence at 90 days compared with the drip and ship model: relative risk (RR) 0.87, 95% CI 0.77 to 0.98. There were no statistically significant differences in relative risk of 90-day mortality, symptomatic ICH or successful reperfusion.
Two additional modelling studies reported differing conclusions on the most appropriate model of care (mothership or drip and ship) for organisation of mechanical thrombectomy services. Only one study accounted for the potential effects of an overwhelming volume of patients in mothership models and local skill reduction in drip and ship models.
A retrospective study (118 hospitals, n=8,533) reported a statistically significant negative correlation between mechanical thrombectomy procedure volume and patient mortality rate: hospitals with higher procedure volume had significantly lower mortality (p=0.007).
Two studies evaluating the learning curve for mechanical thrombectomy found no statistically significant differences in patient outcomes in comparisons of experienced and inexperienced clinicians.
Introducing a mechanical thrombectomy service in Scotland has implications for NHSScotland including costs, staff resources, facility requirements (particularly imaging), ambulance service logistics and general infrastructure.
NHSScotland is required to consider the Scottish Health Technologies Group (SHTG) advice.
What were we asked to look at?
Is mechanical thrombectomy, with or without intravenous thrombolysis, clinically effective compared with standard care for the treatment of ischaemic stroke? If so, does it remain clinically effective if intervention occurs more than 6 hours after symptom onset?
Is mechanical thrombectomy, with or without intravenous thrombolysis, cost effective compared with standard care for the treatment of ischaemic stroke?
What are the organisational issues associated with providing mechanical thrombectomy for patients with ischaemic stroke in Scotland?
Why is this important?
A stroke thrombectomy service is being considered for NHSScotland. Most stroke patients in Scotland are currently managed in integrated stroke units as there are no comprehensive stroke centres. Up until summer 2018, the Western General Hospital in Edinburgh was conducting a small number of thrombectomy procedures in patients with ischaemic stroke. This is the only facility in Scotland to have offered mechanical thrombectomy for ischaemic stroke patients.
Thrombectomy Advisory Group