By Dr Stela Rutovic
ESOC 2023 Session Report – ATTENTION to the BEST and BASIC Controversies of Basilar Artery Occlusion
Chairs: Simona Sacco and Stefania Nannoni
The first lecture in this session was ATTENTION to the Clinical- Anatomical Syndromes of Basilar Artery Occlusion Stroke by Patrik Michel (Lausanne, Switzerland) who presented major differences and similarities between basilar artery occlusion (BAO) strokes and anterior large vessel occlusions (LVO). Frequency of BAO strokes is lower than anterior LVO, its severity has a“ camel distribution „ and severe BAOs are more often missed than anterior LVOs. Symptoms related to missed strokes are acute stupor/coma, isolated vertigo and acute amnesia. Around 50% of BAO strokes have precurser events. Major similarities between anterior LVO and BAO include stroke mechanisms in LVOs and medium vessel occlusions (MEVOs), poor prognosis if untreated, and major outcome predictors including NIHSS, age and recanalisation . Most specific deficits in minor posterior circulation strokes are cerebrellar/vestibular, oculomotor brainstem signs, decreased level of consciousness, bilateral or crosses signs and amnesia. Frequency of LVO and (MEVO) is lower in posterior than anterior circulation. Main clinical syndromes of BAO are top of basilar syndrome as a result of distal BAO, locked-in syndome as mid- basilar occlusion and Wallenberg syndrome as a result of proximal BAO.
The second lecture was The BEST Approach to Imaging Selection of Reperfusion Therapy for Basilar Artery Occlusion by Volker Puetz (Dresden, Germany) . He presented results of recent meta-analysis by Abdalkader et al. which compared endovascular thrombectomy (EVT) with best medical management (BMM) of patients with BAO . The meta-analysis included several randomised control trials (RCTs) (BAOCHE , ATTENTION , BASICS and BEST ) and its results favour EVT in contrast to BMM in BAO. Simple imaging selection criteria for EVT are BAO and pc-ASPECTS≥ 6, and pons- midbrain index ≤2. There is unclear benefit of EVT for BAO if pc-ASPECTS is <6. In the rest of the lecture he provided answers to several questions. The first one was about preferred imaging modality, and the conclusion was that non-contrast CT or CT angiography –source images (CTA-SI) are probably sufficient for patient selection. The second question was should we perform EVT if there is large infarct core (pc-ASPECTS<6). Subgroup analysis from BAOCHE and ATTENTION trial indicate that patients with pc-ASPECTS <6 may benefit from EVT, but future studies are required. Perfusion imaging may identify patients who are unlikely to benefit from EVT. The third question was should EVT be performed in extended time window. Baseline ischemia and collaterals are associated with outcome. Good collaterals and good pc-ASPECTS (>8) may indicate benefit>24h. The fourth question was should we perform EVT in patients with minor deficits (NIHSS <10). Results from the previously mentioned meta -analysis have shown that benefit from EVT in those patients is unclear. CT perfusion may identify patients who are likely to benefit from EVT. The third lecture was The role of Intravenous Thrombolysis for BASILAR Artery Occlusion, by Daniel Strbian (Helsinki, Finland) who gave an overview of several RCTs on the BAO. BASICS registry, BEST and BASIC trials have shown eqvivocal benefit between the treatment of BAO with EVT or IVT, although IVT proved better in BASICS in patients with moderate symptoms. ATTENTION and BAOCHE trial showed that in BAO patients with very severe symptoms EVT is superior to antithrombotics. He pointed out that there is no evidence that EVT is superior to IVT . The only randomised IVT - EVT comparison comes from the BASICS trial in which 80% of patients were treated with IVT, and this trial showed no difference between these treatment modalities. The lecturer further presented observational data from HELSINKI cohort (1995-2022). Favourable outcome in patients treated only with IVT was achieved in 46% of patients (like EVT arms of RCTs). There was no significant difference in outcome between IVT vs EVT, however there was a tendency of more favourable outcome in the IVT group. As a practical guideline he recommended that if you are in a center where you see a patient with very severe BAO symptoms and your standard approach was antiplatelet/anticoagulation EVTshould be used (BEST, BAOCHE, ATTENTION).However, If you are in a center where IVT is used then you should look at BASICS trial and observational data on IVT from HELSINKI. The fourth lecture was Endovascular therapy for BAO: Past, Present and Future by Wouter Schonewille (Utrecht, Netherlands) who gave an overview of major studies on this topic. BASICS registry from 2002.- 2007 included patients with BAO, and showed that there was not favourable outcome of EVT over IVT. Basics Trial from 2012-2019 included patients within 6 hours after stroke onset due to BAO, who were assigned to receive EVT or standard medical care. Chinese ATTENTION registry included patients within 12 hours of estimated BAO, and BAOCHE trial included patients within 6-24h of symptom onset. Both trials only randomized patients with moderate or severe deficit and limited ischemic changes. There was low use of IVT in both trials. There are several conclusions from all of these trials. EVT is highly effecitve in <24 hours from symptom onset in patients with BAO and NIHSS≥10 with limited early ischemic changes not treated with IV T. EVT is probably effective in <4.5hours from symptom onset in patients with BAO and a NIHSS≥10 treated with IVT. The efficacy of additional IVT prior to EVT within 4.5- 24 hours of symptom onset is currently tested in the POST-ETERNAL trial. As a take home message we should be hesitant to treat patients with minor deficit and BAO with EVT, as EVT is potentially harmful in patients with BAO and a NIHSS<10. The efficacy of EVT in patients with a minor deficit should be tested in a future trial. The fifth lecture in this session was Initiation of Anticoagulation After Reperfusion by Apostolos Safoursi (Pireus, Greece). High rates of recurrent cardioembolic strokes within the first days after stroke raise the question if we can initiate anticoagulation early but safely considering the bleeding risk. Results from the studies suggest that during EVT we shoud give as low as possible iv heparin, and that bridging with heparin is not recommended. NOACs are safer and more efficient than VKAs in preventing recurrent strokes and should be the first choice in subacute ischemic stroke. 2019 ESO guidelines suggest initiation of anticoaguation on days 3-4 of stroke onset in patients with mild stroke and small infarct size, on day 7 in those with moderate stroke, and on day 14 in those with severe stroke and large infarct size. Several large studies compared efficacy and safety of early vs late anticogulation in ischemic stroke patients. Recent results of ELAN trial which also included patients after EVT favour early anticoagulation. In accordance with the results of this trial in patients with minor/moderate stroke it could be safe to initiate anticoagulation within 2 days , and in patients with severe stroke in 6 days+1. Hemorrhagic infarction after EVT should not cause delay in the initiation of anticoagulation. There is not many data on optimal timing of anticoagulation in patients with parenchimal hemorrhage after EVD, current results suggest that initiation within 14 days seems safe. [/av_textblock] [/av_one_full]