Microbleeds and Genetic Risk Factors to Predict the Risk of Intracranial Haemorrhage in Patients Treated With Anticoagulation Following Cardioembolic Stroke Due to Atrial Fibrillation

Background Over the last decade, increasing use of oral anticoagulants to prevent cardioembolic ischaemic stroke due to atrial fibrillation (AF) in an ageing population has led to a five-fold increase in the incidence of anticoagulant-related intracranial haemorrhage (ICH) - a rare but unpredictable and catastrophic complication. Cerebral microbleeds (CMBs) on magnetic resonance imaging (MRI) may predict ICH risk, as may genetic polymorphisms influencing brain small-vessel integrity or anticoagulation stability.

Aims To establish the value of CMBs and genetic factors in predicting symptomatic ICH following best practice oral anticoagulation to prevent recurrent ischaemic stroke due to AF.

Methods CROMIS-2: Study I (AF) - Prospective, multicentre, inception cohort study in 1425 patients with ischaemic stroke due to AF started on best practice oral anticoagulation. Patients will have genetic testing and standardized MRI including Gradient recalled Echo (GRE) at baseline, with follow-up by postal questionnaire (and clinical assessment or medical records surveillance after suspected events), and where possible there will be an in person clinical assessment at 2 years. The investigators will compare the rate of symptomatic ICH between CMB and CMB-free patients and test for associations with plausible candidate genes. The investigators aim to develop and validate a risk model to predict symptomatic ICH following best practice oral anticoagulation to prevent recurrent ischaemic stroke due to AF.

CROMIS-2: Study II (ICH) - An observational study of ICH investigating genetic, clinical and radiological risk factors associated with anticoagulant-related ICH. The investigators will recruit patients admitted to participating centres with ICH (with a target of at least 300 anticoagulant-related ICH cases) and collect DNA to increase the power of the genetic studies. The investigators will collect clinical and imaging data from these ICH cases to investigate risk factors associated with anticoagulant-related ICH compared to non anticoagulant-related ICH.

Expected outcomes A successful predictive model for ICH risk after best practice oral anticoagulation for AF will help to determine whether genetic or CMB screening should be used in clinical practice and future trials. New genetic, clinical and radiological risk factors associated with anticoagulant-related ICH will be identified.