By Alan Z. Segal, MD
This randomized trial from China demonstrates a dramatic benefit from endovascular thrombectomy in patients with acute basilar artery occlusion. This benefit was sustained and improved at one year compared to 90 days.
Li R, Tao C, Sun J, et al. Endovascular vs. medical management of acute basilar artery occlusion: A secondary analysis of a randomized clinical trial. JAMA Neurol 2024; Aug 26. doi:10.1001/jamaneurol.2024.2652. [Online ahead of print].
For at least the past 25 years, mechanical thrombectomy has been tried to treat acute ischemic stroke caused by large vessel occlusions (LVOs). However, it was not until 2015 that multiple landmark trials finally proved what long had been presumed — endovascular therapy (EVT) is superior compared to best medical management. The 2015 studies investigated the most common type of LVO, a clot affecting the anterior circulation — distal internal carotid (ICA) or middle cerebral artery (MCA). Other LVOs, most notably basilar artery occlusions (BAOs), continued to be treated with EVT as well, but there was an absence of randomized trial data to support this practice.
In 2020 and 2021, two trials — BEST (performed in China) and BASICS (performed in Europe and the United States) — failed to show benefit for EVT in BAO. The BEST trial was hampered by poor recruitment, and many patients had crossed over to EVT, even after randomization to medical management. The BASICS trial had an unexpectedly high incidence (38%) of favorable outcomes in the medical group, handicapping any possible demonstration of treatment benefit. This unusual result was surprising given that only about 25% of patients with anterior circulation LVOs (and even less with BAO) do well without EVT.
Two studies published in 2023, ATTENTION (Endovascular Treatment for Acute Basilar-Artery Occlusion) and BAOCHE (Basilar Artery Occlusion Chinese Endovascular Trial), both performed in China, established, at long last, a benefit for EVT in BAO. These studies differed in their time windows (many more patients in ATTENTION were treated early — less than 12 hours) but were closely matched in their results. EVT nearly doubled the likelihood of a favorable outcome, increasing from 23% or 24% to 46%.
In the present investigation, the favorable results of ATTENTION were demonstrated to be robust in long-term follow-up — not only matching 90-day results but outperforming medical management at one year. While one-year outcomes meeting the specific study endpoint (modified Rankin Scale score [mRS] of 0-3) were 45% both at 90 days and at one year, the likelihood of the best outcomes (mRS of 0-1) was 28% at one year compared to 20% at 90 days, a statistically significant increase. Among medically treated patients, only 8% achieved this outcome, both at 90 days and at one year. Mortality did increase over time among EVT-treated patients (45% at one year compared with 37% at 90 days). This is not surprising, since there is an expected decreased life expectancy in ischemic stroke survivors. This effect was even higher among medically treated controls, showing a mortality of 55% at 90 days, increasing to 64% at one year. Severely disabled stroke patients are known to be vulnerable to complications such as pneumonia, urinary tract infection, and pulmonary embolism. Because of the “self-fulfilling prophecy” of death as the result of withdrawal of care, these issues might not be aggressively addressed if the neurological outcome already was not acceptable.
Commentary
The results of the ATTENTION trial are dramatically favorable compared to other available data, such as the observational BASILAR registry, which showed one-year mortality rates of 54% in EVT-treated patients and 84% with best medical therapy. As the authors observed, ATTENTION enrolled generally healthier patients than other studies and had an earlier treatment window (less than 12 hours). As with many studies conducted solely in China, ATTENTION (as well as BEST and BAOCHE) may have limited generalizability to Western populations.
The benefit of EVT in BAO must be interpreted in the context of the somewhat controversial definitions of favorable outcomes in stroke trials. Although anterior circulation stroke outcome is considered “good” for an mRS of 0-2, a more permissive definition is used for posterior circulation strokes, with an mRS range of 0-3. This includes patients with moderate disability (able to walk without assistance but requiring significant help in other realms). Given that the mRS is skewed toward motor outcomes, prominent in posterior circulation strokes, it is particularly impressive in ATTENTION that so many patients could achieve an mRS of 0-1. This might reflect the fact that motor function can be aggressively rehabilitated. Other outcomes not represented in the mRS, such as aphasia or neglect, more commonly seen in anterior circulation strokes, may be more difficult to overcome. Patients with anterior circulation strokes with mRS scores of 0-1 may show motor recovery, but they might remain severely impaired as the result of loss of higher-level cortical functions. In contrast, patients with BAO occlusions having an mRS of 0-1 truly may have outstanding outcomes. They would regain the ability to ambulate, along with preservation of cognition.
The current investigation supports the notion that if patients with BAO can be recanalized successfully, they can do extremely well. This result is highly dichotomized compared to a wider variation of anterior circulation stroke outcomes. BAO patients either would do very well (as with as much as 30% of patients in ATTENTION) or die (as with more than 80% of medically treated patients in the BASILAR registry). A “middle ground,” which may or may not reflect a favorable quality of life, would be more typical among the more heterogenous outcomes observed in anterior circulation strokes.
Alan Z. Segal, MD, is Associate Professor of Neurology, Weill Cornell Medicine.
