Is reducing warfarin in patients with brain hemorrhage subsequently putting them at risk of stroke?

This study investigated whether having a brain haemorrhage (a burst brain blood vessel) increases the risk of an ischemic stroke (blood clot in brain) among patients with atrial fibrillation (an abnormal heart beat). 

A stroke occurs when there is a disturbance of blood supply to a part of the brain. This can be caused by a blood clot in the brain (ischemic stroke) or a burst blood vessel (hemorrhagic stroke). Both types of stroke result in a lack of oxygen and food reaching the brain tissue and can cause brain damage.

Atrial fibrillation is an irregular heart beat condition that may cause blood to pool and clot. If a blood clot forms it can be pumped to the brain, blocking off the blood supply and resulting in a stroke.

Warfarin (for example Coumadin, Jantoven) is a drug that stops blood clot formation and is often given to people who are at risk of having a stroke, such as people with atrial fibrillation. However, blood clot formation is a natural way to stop bleeding caused by a burst blood vessel.

When people have a brain hemorrhage, it is necessary to stop the bleeding and allow the blood to clot. Therefore, people who are normally on warfarin because they are at risk of ischemic stroke, have their prescription dose reduced to allow the blood to clot. However, during this time, their risk of forming a blood clot and having an ischemic stroke is increased. 

This study investigated whether people who have had a brain hemorrhage, and as a result have had their warfarin dosage reduced, are more likely to form blood clots and have an ischemic stroke. 

A total of 58,815 patients with atrial fibrillation on warfarin were included in this study. The average age was 73 years. The occurrence of brain hemorrhage and subsequent blood clot formation and ischemic stroke within a 6 month period were recorded.

The study found that the odds of a stroke or blood clot was 4 times higher in people who had a brain hemorrhage, compared to people who did not have a brain hemorrhage. The study also found that overall warfarin prescription was decreased by 72% post-brain hemorrhage compared to before the brain hemorrhage. 

The investigators concluded that a brain hemorrhage was associated with a subsequent increased risk of ischemic stroke and blood clot formation, compared to brain hemorrhage-free patients. They also concluded that the increased risk of ischemic stroke may possibly be due to a decrease or cessation of warfarin prescription in patients with atrial fibrillation. 

This study did not have access all patient clinical records and so it did not compare patients who stayed on warfarin with those that were taken off warfarin to investigate whether those who stayed on warfarin were protected from an ischemic stroke or blood clot.