Mechanical thrombectomy reduces disability and mortality in large strokes in the extended time window

Mechanical thrombectomy (MT) is highly effective in preventing disability in proximal occlusions of the brain-supplying arteries. Previous studies have predominantly included patients with only limited extent of ischaemia on primary imaging. However, especially in the extended or unclear time window, the decision for or against MT in patients presenting with large vessel occlusion and established large ischaemic lesion is frequently necessary in everyday clinical practice.

At the recent World Stroke Congress in Toronto, Götz Thomalla presented the results of the TENSION study (The Efficacy and Safety of Thrombectomy in Stroke with extended lesion and extended time window), which were published simultaneously in The Lancet (1). TENSION is an investigator-initiated, randomised controlled trial that was conducted in 40 centres in Europe and Canada, with funding from the Horizon 2020 Programme of the European Commission. Patients with moderate to severe strokes (NIHSS <26) and occlusion in the M1 segment of the middle cerebral artery or the intracranial segment of the internal carotid artery were enrolled. The intervention had to take place within 12 hours after symptom onset or after the time when the patient was last seen well. Another inclusion criterion was the presence of an established large infarction according to an Alberta Stroke Programme Early CT Score (ASPECTS) of 3 to 5 on non-contrast computed tomography (NCCT) or diffusion-weighted magnetic resonance imaging (DWI-MRI). Patients had to have no higher degree of pre-morbid disability (modified Rankin Scale 0-2) and no contraindications for MT or indication for emergent stenting. Patients were randomised in a 1:1 fashion into either best medical treatment alone or MT plus best medical treatment. The primary endpoint was functional outcome using an ordinal mRS shift analysis at 90 days after inclusion in the intention-to-treat population. Additional endpoints included quality of life measures and symptomatic intracranial haemorrhage. The sample size was specified as 665 at the time of study design including interim analyses after one third and two third of patients had completed outcome evaluation. The study was terminated early after the first interim analyses because the efficacy endpoint has been met. Until then, 253 patients were randomized. Baseline characteristics did not differ considerably between groups. The median NIHSS was 19 and 18, respectively, and the median premorbid mRS was 0 in both groups. In the intervention group, successful reperfusion (corresponding to mTICI 2b, or better) was achieved in 83% of cases. There was a substantial shift in the mRS distribution in favour of MT (common odds ratio (OR): 2.58; 95% confidence interval: 1.60-4.15). 39 patients (31%) in the MT group achieved an mRS of 0 to 3 at 90 days compared with 16 patients (13%) in the control group (OR: 2.84, 95% confidence interval: 1.48-5.47). Secondary patient-reported health and quality of life outcomes also yielded benefits of MT. Mortality at 90 days was 49 (40%) in the intervention arm and 63 (51%) in patients treated with medical treatment alone (hazard ratio: 0.67; 95% confidence interval: 0.46-0.98). Symptomatic intracranial haemorrhages occurred in 5% of cases in both groups. In conclusion, MT is safe and effective in terms of functional outcome and mortality in patients with large vessel occlusions and established large infarcts. Recently, already three randomised trials (2-4) demonstrated the efficacy of MT in the management of proximal vessel occlusions and large infarcts. The TENSION study has now pursued a strictly pragmatic approach in refraining from using multimodal imaging to identify penumbra tissue, but instead applying NCCT - or more occasionally DWI - as the basis for the assessment of ASPECTS. No additional software for post-processing was applied in this setting. The clearly beneficial effects of MT were nonetheless comparable to those of the previous studies. It should be emphasised that not only deaths were substantially prevented by MT, but also a significant proportion of patients were able to achieve a favourable functional outcome without relevant disability despite the adverse initial situation. It is furthermore reassuring that these intriguing results were not contradicted by an increased rate of haemorrhages. TENSION thus teaches us that sophisticated imaging methods are not strictly mandatory to guide the optimal therapy in patients with a large infarct core in the extended time window.

References:

1. Bendszus M, Fiehler J, Subtil F, et al. Endovascular thrombectomy for acute ischaemic stroke with established large infarct: multicentre, open-label, randomised trial. 2023 Oct 10:S0140-6736(23)02032-9. doi: 10.1016/S0140-6736(23)02032-9. Epub ahead of print.
2. Yoshimura S, Sakai N, Yamagami H, et al. Endovascular therapy for acute stroke with a large ischemic region. N Engl J Med 2022; 386: 1303–13.
3. Sarraj A, Hassan AE, Abraham MG, et al. Trial of endovascular thrombectomy for large ischemic strokes. N Engl J Med 2023;388: 1259–71.
4. Huo X, Ma G, Tong X, et al. Trial of endovascular therapy for acute ischemic stroke with large infarct. N Engl J Med 2023; 388: 1272–83.