Agreement: I Agree Body: Dear Editor Yuan and colleagues provide valuable evidence on head positioning after successful endovascular thrombectomy. We wonder, however, whether angiographic reperfusion alone is sufficient to support the suggestion that successful reperfusion substantially reduces the haemodynamic relevance of head position. Angiographic reperfusion does not necessarily imply restoration of tissue-level perfusion. In HeadSOAR, successful reperfusion was defined as an expanded Thrombolysis in Cerebral Infarction (eTICI) score of ≥2b. The authors reasonably suggest that improved cerebral blood flow and autoregulation after reperfusion might attenuate any perfusion advantage associated with a flat head position. However, eTICI is an angiographic measure of territorial reperfusion and does not directly quantify capillary or parenchymal perfusion. A recent systematic review and meta-analysis estimated that no-reflow occurred in 29% of patients despite successful macrovascular reperfusion and was associated with substantially lower odds of functional independence.[1] Nicolini and colleagues likewise identified no-reflow after endovascular treatment and found associations with impaired early neurological improvement and haemorrhagic transformation.[2] Recent perfusion imaging studies further illustrate this dissociation. Rivet and colleagues identified persistent tissue-level hypoperfusion despite near-complete or complete angiographic reperfusion (eTICI 2c-3), and these patients had poorer 90-day outcomes than those with effective tissue reperfusion.[3] Horie and colleagues similarly reported residual haemodynamic impairment shortly after successful thrombectomy, with reduced cerebral blood flow associated with poorer subsequent outcomes.[4] These findings suggest that apparently successful angiographic reperfusion may encompass physiologically heterogeneous states. The physiological evidence supporting reduced positional sensitivity after recanalisation is also limited. The HOBOE study included only eight patients, four with complete recanalisation, and assessed cerebral haemodynamics using transcranial Doppler rather than tissue perfusion imaging.[5] A related but distinct concern is that cerebral autoregulation may remain impaired despite successful reperfusion. Ran and colleagues found persistent impairment of dynamic cerebral autoregulation in some patients after successful thrombectomy, which was associated with poorer functional outcome.[6] These observations do not establish that patients with residual hypoperfusion are necessarily more responsive to head positioning, but they question whether angiographic success uniformly indicates haemodynamic stability. Notably, HeadSOAR found no clear interaction between angiographic eTICI grade and treatment effect (P for interaction=0.14). However, absence of interaction across angiographic grades does not exclude tissue-level heterogeneity within each grade. Patients with similar eTICI scores may differ in microvascular perfusion and autoregulatory capacity. The neutral overall findings of HeadSOAR therefore need not imply that cerebral haemodynamics after thrombectomy are uniformly insensitive to head position. Future trials could incorporate CT or MR perfusion imaging immediately after thrombectomy and, ideally, before randomisation, allowing prespecified assessment of whether tissue reperfusion status modifies the effect of head positioning. Complementing angiographic grading with tissue-level perfusion assessment may provide a more physiologically informative framework for interpreting head-position effects after thrombectomy. [1] Mujanovic A, Ng F, Meinel TR, et al. No-reflow phenomenon in stroke patients: a systematic literature review and meta-analysis of clinical data. Int J Stroke. 2024;19(1):58-67. doi:10.1177/17474930231180434. [2] Nicolini E, Iacobucci M, De Michele M, et al. No-reflow phenomenon in acute ischemic stroke: an angiographic evaluation. Neurol Sci. 2023;44(11):3939-3948. doi:10.1007/s10072-023-06879-6. [3] Rivet S, Churilov L, Yassi N, et al. Persistent tissue-level hypoperfusion (no-reflow) negates the clinical benefit of successful thrombectomy. Stroke. 2025;56(6):1451-1459. doi:10.1161/STROKEAHA.124.049574. [4] Horie N, Inoue M, Morimoto T, et al. Recanalization does not always equate to reperfusion: no-reflow phenomenon after successful thrombectomy. Stroke. 2025;56(1):183-189. doi:10.1161/STROKEAHA.124.048994. [5] Hunter AJ, Snodgrass SJ, Quain D, et al. HOBOE (Head-of-Bed Optimization of Elevation) Study: association of higher angle with reduced cerebral blood flow velocity in acute ischemic stroke. Phys Ther. 2011;91:1503-1512. doi:10.2522/ptj.20100271. [6] Ran L, Wang P, Chen H, et al. Compromised dynamic cerebral autoregulation is a hemodynamic marker for predicting poor prognosis even with good recanalization after endovascular thrombectomy. Brain Circ. 2024;10(1):77-84. doi:10.4103/bc.bc_83_23. No competing Interests: Yes The following competing Interests: Electronic Publication Date: Saturday, August 22, 2026 - 07:33 AI use: Yes I have used AI AI use details: Improve spelling and grammar. Highwire Comment Subject: Head positioning after endovascular therapy for acute stroke due to large vessel occlusion (HeadSOAR): multicentre randomised controlled trial Workflow State: Released Full Title: Angiographic reperfusion may not capture tissue-level haemodynamic heterogeneity after thrombectomy Highwire Comment Response to: Head positioning after endovascular therapy for acute stroke due to large vessel occlusion (HeadSOAR): multicentre randomised controlled trial Check this box if you would like your letter to appear anonymously:: Last Name: Ru First name and middle initial: Yifei Email: ruyf@alumni.sysu.edu.cn Address: Guangzhou, China Occupation: Neurosurgery MD Student Affiliation: The First Affiliated Hospital of Sun Yat-sen University BMJ: Additional Article Info: Rapid response
Angiographic reperfusion may not capture tissue-level haemodynamic heterogeneity after thrombectomy
