Anticoagulants act by delaying the ability of blood to form clots. Doctors commonly refer to them as ‘blood thinners’ however strictly speaking they don’t thin the blood but merely reduce the ability for the blood to clot.
Commonly used anticoagulants which can be taken orally include Warfarin and the NOACs. There is an anticoagulant which can be used as an injection called Heparin but it is impractical to use this on a long term basis in patients with AF when oral agents are available.
It is useful to gain an understanding of anticoagulants and their role in AF. Anticoagulants don’t improve symptoms or quality of life in AF. They simply act to reduce the risk of strokes. In this sense they can be likened to the seatbelt in our cars. We wear the seatbelt not because it in someway improves our quality of life but more so because it could reduce the risk of serious harm if we were unfortunate enough to be involved in an accident. It is also true to say that there will be some people who don’t wear a seatbelt and yet escape unscathed from an accident and there will be some people who will be seriously injured in an accident despite wearing a seatbelt.
Anticoagulation in AF is similar to wearing a seatbelt. Some people with AF and a high CHADS2VASC score may not have a stroke even if they don’t take anticoagulants and some people with AF could still have a stroke despite taking anticoagulants. There are unfortunately no guarantees. The individual patient taking an anticoagulant will also never know whether they would definitely have had a stroke if they weren’t taking the anticoagulant and this why we have to look to clinical studies to guide us as to what happens to a population of patients just like us with AF if they take anticoagulants compared to if they don’t. Several very large scale studies have consistently shown that taking an anticoagulant can reduce the risk of strokes by 60% and this is why anticoagulants are so strongly recommended in patients with AF and a raised CHADS2VASC score.
The most recent guidance from the National Institute of Clinical Excellence (NICE) is that male patients with a CHADS2VASC score of 1 or more and females with a CHADS2VASC score of 2 or more should take an anticoagulant for life.
The most recent guidance from the European Society of Cardiology is that anticoagulation should be considered in male patients with a CHADS2VASC score of 1 or more and females with a CHADS2VASC score of 2 and should be recommended in male patients with a CHADS2VASC score of 2 or more and in female patinets with a CHADS2VASC score of 3 or more.
Unlike car seat-belts however, anticoagulants are not completely harmless and do increase the risk of bleeding. Bleeding from anticoagulants may be secondary to an injury but can also be spontaneous. Bleeding may be minor but can also occasionally be major. Whilst minor bleeding such as from cuts and brusies, spontaneous nose and gum bleeds and haemorrhodal bleeds are usually self limiting and not serious, major bleeding can be extremely dangerous and life-threatening. There are 2 main places where life-threatening major bleeding can occur.
- The gastrointestinal tract (gastric bleeding)
- The brain (Intracranial bleeding)
Gastric bleeding is usually not as dangerous as intracranial bleeding because usually one would need to lose a large amount of blood in the gastrointestinal tract to become life threatening and usually the gastrointestinal tract is easily accessible for doctors to look in and treat. Intracranial bleeding however is much more dangerous because only a very small amount of blood can cause significant long term disability or even death. Also the brain is not as easily accessible for doctors as the stomach
Unfortunately there is no way to completely safeguard against the risk of bleeding and this is why trying to balance the risk of bleeding against the risk of strokes can be such a challenging dilemma for both the doctor and the patient. For the patient it is often like being caught between a rock and a hard place. For the majority of patients the risk of bleeding is lower than the risk of stroke. However doctors often use an aide-memoire called HASBLED to identify if patients are at an excessively higher risk of bleeding and if the bleeding risk can be modified in someway