Predictors of Intracranial Hemorrhage Volume Expansion in Patients Receiving Factor Xa Inhibitors in ANNEXA‐4: Time and Severity Matter Most

Background Andexanet alfa, a specific reversal agent for factor Xa inhibitors, resulted in effective hemostasis in 79% of patients with intracranial bleeding in the ANNEXA‐4 (Andexanet Alfa, a Novel Antidote to the Anticoagulation Effects of Factor Xa Inhibitors) trial (NCT02329327). However, little is known about predictors associated with hematoma expansion in patients with factor Xa inhibitor–associated intracranial hemorrhage (ICrH) receiving andexanet alfa. Methods The ANNEXA‐4 trial was a prospective, single‐arm, open‐label study of andexanet alfa in patients with acute major bleeding within 18 hours after taking a factor Xa inhibitor. Hematoma volumes at baseline and 12 hours after andexanet alfa treatment were measured using a computerized‐assisted volumetric method. Univariable and multivariable logistic regression analyses of clinical and nonclinical parameters were performed to identify factors predictive of different volumes of hematoma expansion. To this end, an ICrH Expansion Scale was developed. Results Overall, 305 ANNEXA‐4 study patients with baseline and follow‐up imaging were included, 15.7% of whom showed evidence of any ICrH expansion ≥6‐mL. Patients with ≥6‐mL ICrH expansion had a significantly (P