Abstract TP301: Warfarin Increases Risk of Future Intracerebral Hemorrhage in Patients Presenting with Isolated Lobar Microbleeds on MRI

Abstract

BACKGROUND/OBJECTIVES: Lobar microbleeds (LMB) are increasingly identified on brain MRI of older adults, suggesting a diagnosis of cerebral amyloid angiopathy (CAA) in the absence of intracerebral hemorrhage (ICH). Identifying the baseline characteristics and risk of future ICH of these subjects is important to understand their prognosis and safety of antithrombotic use in this setting. METHODS: Baseline characteristics (demographics, risk factors, APOE genotype), markers of CAA severity (LMB counts, white matter hyperintensity volume), and finally outcomes during a mean follow up of 4 years (incidence rate of ICH and case-fatality) were compared between 62 CAA patients without and 747 with ICH diagnosed using Boston criteria upon enrollment. The association between antithrombotic use and risk of incident ICH was explored in patients presenting with isolated LMBs after adjusting for covariates listed above. RESULTS: Female gender (52% vs. 37% p=0.023) and hypertension (67% vs. 53% p=0.025) were more common in patients presenting with ICH, other baseline characteristics did not differ. Patients presenting without ICH had more LMBs (median 10 vs. 1 p<0.001), and higher white matter hyperintensity volume (38cc±32 vs. 27cc ±24 p=0.008) than patients with ICH even after correction for other covariates. Patients without ICH on enrollment had a lower but non-trivial incidence rate of ICH during follow-up (4.8 per 100 person-years vs. 9 per 100 person-years; RR: 0.56, 95%CI 0.27-0.97). The case-fatality rates were similar between these groups (p=0.5). In patients presenting without ICH, the use of Warfarin was an independent predictor of future ICH (p=0.02) in the multivariate model. Patients using either ASA 325mg/day OR Clopidogrel OR ASA/Dipyridamol had higher risk of future ICH (p=.049) but this association did not remain significant in multivariate model. Use of ASA 81mg daily was not a predictor of incident ICH risk. CONCLUSIONS: Patients presenting with LMBs on MRI have a clinical, genetic, and neuroimaging profile suggestive of severe CAA pathology. They have a considerable risk of incident ICH albeit lower than patients who had a prior lobar ICH. The use of warfarin increases the risk of future ICH in patients with isolated LMBs on MRI.