Hypoplastic Vertebral Artery Contributes to Stroke by Promoting Progression of Basilar Artery Bending

ABSTRACT Background As a well‐recognized vascular variation, hypoplastic vertebral artery has been recognized as a potential risk for stroke. We aimed to assess the odds of new‐onset stroke over a 20‐year period in subjects with versus without hypoplastic vertebral artery, exploring how the progression of basilar artery bending mediates the odds. Methods This was a retrospective cohort study, with 20 years of follow‐up (2004–2024, analysis performed in June 2025). The primary outcome was the occurrence of new‐onset posterior circulation infarction during follow‐up. Logistic regression models were fitted for new‐onset posterior circulation infarction as gender, baseline stroke, baseline posterior circulation infarction, basilar artery stenosis during follow‐up, the progression of basilar artery bending, and hypoplastic vertebral artery. Mediation analyses were conducted for vertebral artery stenosis during follow‐up, basilar artery stenosis during follow‐up, and the progression of basilar artery bending. Results A total of 1464 subjects were included, 547 with hypoplastic vertebral artery. During the 20‐year follow‐up, 91 participants had new‐onset posterior circulation infarction. The occurrence of new‐onset posterior circulation infarction was significantly associated with progression of basilar artery bending (odds ratio 1.700, 95% confidence interval 1.032–2.798, p = 0.037) and hypoplastic vertebral artery (odds ratio 1.481, 95% confidence interval 1.019–2.003, p = 0.015). The proportion of new‐onset posterior circulation infarction attributable to hypoplastic vertebral artery was mediated by the progression of basilar artery bending, accounting for approximately 50.2% (95% confidence interval 3.2%–102.4%). Conclusions Results of this study revealed that hypoplastic vertebral artery was associated with new‐onset posterior circulation infarction, and progression of basilar artery bending may serve as a potential intermediate factor in this association.