Atrial fibrillation is a condition where the heart beats irregularly, which can lead to a clot forming in the heart chambers. This clot can travel up to block a blood vessel in the brain, causing a stroke. After this type of stroke, warfarin is often prescribed to prevent blood clotting and further stroke. Whilst this drug is very effective and widely used, it has the very rare side-effect of causing bleeding in the brain (haemorrhage). In some cases, it can be very difficult to accurately assess the risks and benefits of anticoagulation.
Very small bleeds in the brain, microbleeds, are now seen in about a quarter of people with stroke due to a blocked artery using a brain scan called gradient-echo magnetic resonance imaging (MRI). Previous research has suggested that having microbleeds increases the risk of future brain haemorrhage, which can be devastating and often lead to severe disability or death.
This study will test the theory that microbleeds may be useful in assessing the risk of haemorrhage after starting warfarin, by using MRI scans to investigate whether stroke survivors have microbleeds prior to starting warfarin. Specifically, the study will assess a large number of stroke survivors who have had a stroke due to atrial fibrillation to identify whether people with microbleeds are at higher risk of developing a brain haemorrhage whilst taking warfarin. By identifying those at risk, precautions can be taken and potentially fatal brain haemorrhages could be prevented.