Reasons you may be taking an oral anticoagulant

The human body has a complex mechanism called coagulation that causes blood to clot if a wound occurs. Under normal circumstances this is desirable; it allows the body to heal itself. Yet in some clinical conditions, coagulation can cause unwanted blood clots that can be life threatening.

These are some common reasons why a blood clot forms and why an anticoagulant may be prescribed:

  • Atrial fibrillation (irregular heartbeat)
  • Mechanical or artificial heart valves – can cause a "foreign body" reaction.
  • Deep Vein Thrombosis (DVT) – slow-moving or stationary blood in a vein deep within a muscle of the leg or pelvis. (blood clot)
  • Heart attack causing damage to heart muscle.
  • Stroke

If a blood clot (thrombus) develops due to any of the above causes, there is a risk that it may "break off" and move to another part of the body where it can cause a blockage and further damage.

To read more about these conditions, download our information booklet listed in the right-hand column.

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Atrial Fibrillation (AF)

AF is a disorder of the heart rhythm and is common in older people (it affects nearly 10% of people over 80). In healthy individuals, a regular heart rate of between 60 and 100 beats per minute at rest is normal, but patients with AF may have periods of very low or very high heart rate (up to 175 beats per minute).

In the heart of a person with AF, the heart quivers, or fibrillates, rapidly and irregularly rather than beating effectively. This leads to symptoms such as palpitations and shortness of breath. It also means that blood flow within the heart itself can become sluggish and there is a risk of clot formation on the walls lining the heart, especially within the chamber known as the atrium.  This can lead to a heart attack.

Anticoagulants lengthen the time it takes for blood to clot, and therefore reduce the risk of a clot developing.

Mechanical Heart valve replacement

Modern heart surgery has transformed the lives of many people who were either born with, or developed as they grew older, damaged heart valves. When heart valves are damaged, the problem is either that the valve is narrowed or that it no longer fully closes.

They can now be replaced with either a ‘biological’ valve, e.g. a pig heart valve treated for use in humans, or a mechanical valve made out of synthetic material.

Mechanical heart valves are more durable, however there is an increased risk of clot formation. To reduce the risk of clotting your doctor may prescribe an oral anticoagulant.

Deep Vein Thrombosis and Pulmonary Embolism

Deep Vein Thrombosis (DVT) occurs when a blood clot forms in a vein. It usually develops in the calf muscle, less frequently in the thigh and sometimes in other deep-lying veins in your body.

Some of the common symptoms of a DVT are:

  • Tenderness in the leg
  • Redness
  • Swelling and a feeling of tightness, the skin may feel "stretched".
  • Pain
  • However some DVTs have no symptoms at all.

There may be increased risk of DVT under conditions of:

  • Prolonged immobility, for example long journeys where you sit still without being able to stretch your legs or move about
  • A medical condition that restricts normal movement or activity
  • Surgery such as orthopaedic surgery or illness that requires treatment such as chemotherapy
  • Genetic or inherited conditions
  • Existing vein damage from a previous DVT
  • The contraceptive pill and hormone replacement therapy
  • Pregnancy

Some people may only realise they have a DVT when a pulmonary embolism develops as a result of the blood clot in the leg breaking away and being carried to the lungs in the blood stream. Pulmonary Embolism is a very serious condition.

A Pulmonary Embolism (PE) is a blood clot in the lung that usually originates from smaller blood vessels in the leg. A clot from a DVT travels to the lungs and through the vessels of the lung until it reaches smaller vessels where it becomes lodged. The clot then prevents any further blood from travelling to that section of the lung which can eventually lead to stroke.

Common symptoms may include:

  • Chest pain that is sharp and is worse when taking a deep breath
  • Shortness of breath
  • Low blood pressure
  • Sweating
  • Anxiety

All the above can also be symptoms for other conditions; however Pulmonary Embolism can be life threatening so if you are concerned, seek the advice of a doctor or go to your nearest accident and emergency department.

People that experience a PE may be in hospital for several days until their anticoagulant medication is introduced and stabilised. They may remain on anticoagulation therapy for six months or longer.