1213. Size as an Independent Predictor of Arteriovenous Malformation Presentation with Hemorrhage

Authors: James Feghali; Wuyang Yang; Jason Liew; Risheng Xu, MD, PhD; Justin Caplan, MD; Rafael Tamargo, MD; Judy Huang, MD (Baltimore, )

Introduction: The natural history of arteriovenous malformations (AVM) is still poorly understood. Lesion size has been investigated in the context of hemorrhage risk prediction, and results have been inconsistent. This study aims to illustrate the association between size and rupture of AVMs at presentation in a large sample of patients while accounting for other risk factors. Methods: We conducted a retrospective chart review of AVM patients seen at our institution between 1990 and 2018. AVM size was categorized as small(<3cm) versus large(≥3cm) and rupture rates at presentation were compared between both groups. The same analysis was repeated twice, stratifying first by race(white or nonwhite) and then by deep venous drainage(present or absent). Comparisons were made using Pearson's chi-squared test. Finally, logistic regression incorporating size, race, and venous drainage was performed. Results: We reviewed 709 patients including 374(52.8%) with small AVMs and 335(47.2%) with large AVMs; the percentage of patients presenting with hemorrhage was 36%. Smaller AVMs were more likely to present with rupture(OR=2.06, p <0.001). Stratifying by race, smaller size was also associated with higher risk of hemorrhage at presentation among both white(OR=2.18, p <0.001) and non-white(OR=1.85, p =0.023) patients. Stratifying by venous drainage, smaller size was also associated with increased rupture risk among both AVMs with deep drainage(OR=2.38, p <0.001) and those without deep drainage(OR=1.81, p =0.012). Controlling for both race and venous drainage through logistic regression, smaller size was significantly associated with increased risk of hemorrhage at presentation(adjusted OR=1.903, p <0.001). Conclusion: AVM size less than 3 cm is associated with a two-fold higher odds of presenting with hemorrhage than larger AVMs, confirming a role for nidus size in independently predicting AVM hemorrhage. The underlying hemodynamic differences that may characterize this distinction remain to be elucidated.