ASCOD phenotyping of acute vertebrobasilar artery occlusion treated by mechanical thrombectomy: insight from the PERSIST registry
Authors: Hu Miaomiao , Xu Yingjie , Huang Kai , Luan Huanhuan , Zuo Kun , Liu Yuanlu , Wang Songlin , Wang Meng , Zhang Pan , Chen Hao , Sun Wen 
Published: April 2024

OBJECTIVE
Determining the underlying etiology of acute vertebrobasilar artery occlusion (VBAO) is crucial for selecting an appropriate treatment approach. The authors aimed to investigate the distribution of etiology and the association with functional outcomes in patients with acute VBAO who underwent endovascular treatment in which atherosclerosis, small-vessel disease, cardiac pathology, other causes, and dissection (ASCOD) phenotyping was used.

METHODS
A retrospective study was conducted at 21 centers in China, involving patients with VBAO who received endovascular treatment within 24 hours of the estimated occlusion time. In the ASCOD phenotyping, each phenotype is graded based on the following categories: 1, likely to be causal; 2, uncertain if causal; and 3, unlikely to be causal. The authors defined a single possible cause as a cause graded 1 in a single domain, and multiple possible causes were graded 1 or 2 regardless of overlap. The primary outcome was unfavorable outcome (modified Rankin Scale [mRS] score of 3–6) at 90 days. The secondary outcomes included shift of mRS score at 90 days, 90-day mortality, successful reperfusion, and National Institutes of Health Stroke Scale score at 24 hours. Multivariable regression analysis was used to assess the association between etiological subtypes and functional outcomes. Multivariate competing-risk regression analysis was performed to analyze the association between etiological subtypes and the risk of recurrent stroke.

RESULTS
A total of 577 patients were included in this study. Of these, 521 (90%) had a single possible cause. The most common etiology was A1 (382 cases, 73%), followed by C1 (111 cases, 21%) and O1 (28 cases, 5%—in this study the other causes and dissection subtypes were categorized under the umbrella term of "O" causes). Similar patterns were observed in the multiple possible causes. In the baseline characteristics of the cohort, as rescue therapy, stenting was more frequently used in patients in the A1 group than in the C1 group (53.2% vs 41.7%; p < 0.01). The proportion of atherosclerosis-type etiology increased when the occlusion was located more proximally (p < 0.01). Compared to the A1 group, patients in the C1 group had a lower incidence of unfavorable outcome (OR 0.42, 95% CI 0.24–0.73), which was less likely to shift to a worse mRS score (OR 0.60, 95% CI 0.39–0.91). The O1 subtype was not associated with unfavorable outcome (OR 1.35, 95% CI 0.46–4.01), whereas patients with the O1 subtype were more likely to shift to worse mRS score (OR 2.39, 95% CI 1.09–5.25) and to have a higher 90-day mortality rate (OR 2.60, 95% CI 1.07–6.31). Furthermore, there was no significant association between single etiological subtypes and stroke recurrence within 1 year.

CONCLUSIONS
The most common etiology in patients with VBAO was atherosclerosis, followed by cardiac pathology and other. Compared to the A1 subgroup, the C1 subgroup showed better functional outcomes, whereas the O1 subgroup showed worse outcomes. Additionally, there was no statistically significant difference in the recurrence risk.