<Background>  	Risk of devastating intracerebral haemorrhage (ICH) is the main factor limiting use of anticoagulants in atrial fibrillation (AF). MRI detection of cerebral microbleeds (CMBs), which predicts future ICH, may help guide anticoagulant decisions. 

<Aims> 	We aim to evaluate the risk of warfarin-associated ICH in Chinese AF patients with CMBs, who have higher risk of ICH compared with Caucasians.

<Methods>	This is a prospective multi-centre observational study. Inclusion criteria were Chinese AF patients aged over 18 years, who required warfarin for stroke prevention. Exclusion criteria included contra-indications for MRI, patients with bleeding tendency, concurrent treatment with other anti-coagulants or anti-platelet agents.
All patients underwent 3T MRI brain for evaluation of CMBs and Age Related White Matter Changes (ARWMC) scale. Patients were followed-up clinically for 2 years. Primary outcome was clinical ICH. Secondary outcomes were ischaemic stroke, systemic embolism, mortality of all causes and modified Rankin Scale ≥3.

<Results>		We included 237 patients in final analysis. The mean follow-up period was 22.7 ± 10.3 months. Mean time within therapeutic range (TTR) was 52.3 ± 21.1 %. CMBs were present in 84 (35.4%) of patients, 11 patients had ≥5 CMBs. 
Compared with patients without CMBs, patients with CMBs had numerically higher rate of primary and secondary outcome events. Rate of ICH among patients with CMBs (18.5 per 1000 patient years) was much higher than that observed in Caucasian cohorts. Also, patients with 5 CMBs were associated with more ICH than ischaemic stroke. Compared with ARWMC, HAS-BLED and CHA2DS2-VASc, CMBs was more sensitive in predicting ICH at follow-up.

<Conclusion>	This is the first study evaluating risk of warfarin-associated ICH in Chinese AF patients with CMBs. Presence of multiple CMBs may be associated with higher rate of ICH than ischaemic stroke. Larger studies through international collaboration are needed to determine the risk-to-benefit ratio of warfarin in AF patients with CMBs of different ethnic origin.

Risk of Intracerebral Haemorrhage in Chinese Patients Taking Oral Anticoagulants for Atrial Fibrillation with Cerebral Microbleeds. A Prospective Study in Warfarin. (IPAAC - Warfarin Study)