Atrial fibrillation is a rapid heart beat that increases the chance of blood clots and stroke. It is the most common abnormal heart rhythm and people often won't even notice they have it. Some people may notice heart palpitations, fainting or chest pain.

Atrial fibrillation increases a person's risk of stroke because the heart isn't pumping as effectively and blood may pool and form clots in the heart. It is when these clots break off and travel to the brain that a stroke may occur.

Anticoagulant therapy greatly reduces the chance of these blood clots forming and so greatly reduces the chance of a stroke.

Deep vein thrombosis is the formation of a blood clot in a deep vein. It most commonly affects the veins in the leg. DVT may be asymptomatic, but the classic symptoms include pain, swelling and redness of the leg.

The most common reason for developing DVT is recent surgery or hospitalisation where you can't move around a lot and keep your blood flowing. DVT can increase the risk of stroke and pulmonary embolism. This is because the blood clot may break off and travel through the blood to the brain or the lungs and block the blood flow to these areas.

The usual treatment for DVT is anticoagulation to reduce the chance of any complications.

A pulmonary embolism is a blockage of either the pulmonary artery or one of its branches (the pulmonary artery is the blood vessel that carries blood from your heart to your lungs). A PE usually occurs when a blood clot from DVT breaks off and travels through the blood to the lungs.

Symptoms of PE usually come on suddenly and may include difficulty breathing, pain in the chest during breathing, and cough.

Anticoagulants are the main treatment of PE to try and get rid of the clot and prevent another forming.