Blood clotting & thrombosis

Blood clotting is an essential part of the body’s repair mechanism. When you injure yourself, which damages the walls of blood vessels, blood clots form to block any holes in the damaged walls, preventing excessive blood loss. Once the injury is healed, the blood clots are no longer required and naturally dissolve. 

However, clots can sometimes form inside the blood vessels without any injuries, or fail to dissolve after an injury is healed. This abnormal blood clotting is known as thrombosis. The clot blocks the blood vessel where it is formed, preventing blood flow and the essential delivery of oxygen to parts of your body, causing cells to die. Additionally, little parts of a blood clot can break off and travel through blood vessels elsewhere in the body to block even smaller vasculature, known as an embolism. 

When a blood clot blocks major arteries providing blood to the brain and heart, an ischemic stroke (stroke due to lack of blood flow to the brain) or heart attack may occur, leading to a life-threatening condition unless immediate medical assistance is obtained.¹ 

What is thrombophilia?

Thrombophilia is a blood condition that increases the risk of thrombosis – an abnormal blood clotting that may block blood vessels. It can be inherited from a person’s family (genetic thrombophilia) or caused later in life due to other medical conditions (acquired thrombophilia). However, people with thrombophilia do not always experience thrombosis, particularly if risk factors are identified and managed early. 

The following article will discuss how the risk of abnormal blood clotting can be reduced in persons at high risk of thrombophilia.

Genetic thrombophilia

People with genetic thrombophilia inherit a gene causing abnormal blood clotting from one or both parents. The most common blood clotting disorder is Factor V Leiden, caused by a mutation in the coagulation factor F5 gene. The F5 gene produces the protein Factor V, which assists blood clot formation. Mutations in the F5 gene increase the likelihood of deep vein thrombosis. 

Another common cause of genetic thrombophilia is mutations in the prothrombin gene. Also known as Factor II, prothrombin is a protein encoded by the coagulation factor F2 gene. Due to prothrombin’s role in blood clot formation, mutations in this gene increase the risk of deep vein thrombosis and pulmonary embolism. 

Acquired thrombophilia

Acquired thrombophilia is more common than genetic thrombophilia. It can be caused by pre-existing medical conditions, including cancer, obesity, diabetes, high blood pressure, high blood cholesterol, and atherosclerosis (buildup of fatty deposits leading to the narrowing of blood vessels). An increase in levels of the hormone estrogen, potentially due to birth control pills, pregnancy, or hormone replacement therapy, may increase the risk of abnormal blood clotting.² Behavioural factors, such as smoking and prolonged periods of immobility, also increase the risk of thrombosis.¹ 

The most common acquired thrombophilia is antiphospholipid syndrome, also known as Hughes syndrome. It is an autoimmune disease –a condition whereby the person’s immune system mistakenly attacks parts of their own body. In this case, proteins bound to the fat molecules known as phospholipids cause antibodies (proteins which tell the immune system what cells to attack) to attach and attack the phospholipid proteins, enhancing the expression of coagulation factors (proteins which cause blood clotting). This increases the risk of blood clotting, which may lead to thrombosis in both arteries and veins. Strokes, heart attacks, and miscarriages (a loss of pregnancy) if a clot blocks the blood flow to the placenta (a temporary organ providing nutrients to the foetus) may occur.

Diagnosing thrombophilia 

Most people don’t discover they have thrombophilia until abnormal blood clotting occurs. Moreover, the symptoms of thrombosis differ greatly according to the location of clotting and downstream effects. Therefore, if thrombophilia is not identified and managed promptly, the blood clots may cause potentially life-threatening complications.

The symptoms of how different areas of the body react to thrombosis are outlined below:

The heart

Thrombosis may block the coronary arteries, which supply oxygenated blood to the heart. This may cause angina (pain in the chest), shortness of breath, and fatigue (feeling of tiredness) due to reduced oxygen delivery. If coronary arteries are completely blocked, a heart attack may occur. The pain in the chest may spread to the upper body or extremities, and there may also be sweating, nausea, light-headedness, and an overwhelming feeling of anxiety. If this occurs, emergency services must be called immediately. Resting while waiting for an ambulance reduces unnecessary strain on the heart, improving the likelihood of survival.³

The brain

Blood vessels supplying blood to the brain include the carotid arteries (located at the sides of the neck) and vertebral arteries (located in the spinal column). Thrombosis in these arteries interrupts this blood supply, which may cause an ischemic stroke. 

Symptoms and response to a stroke can be remembered through the acronym BE FAST:⁴

• Balance - The person may have trouble standing upright
• Eyes -The person may have blurry or double vision
• Face -The person may have one or both sides of their face droop when smiling
• Arms - When raising their arms, one or both of the person’s arms may droop downwards
• Speech - The person may have slurred speech or difficulty choosing their words
• Time -If someone is suspected of having a stroke, emergency services should be called immediately. This allows the person to receive treatment as soon as possible, improving their chances of survival

Transient ischemic stroke may also occur. Also known as a mini-stroke, blood supply to the brain is temporarily disrupted by a blood clot before the blood clot dissolves, restoring blood flow. Although it is shorter-lasting than a stroke, early symptoms of a mini-stroke are identical to a full stroke. Emergency services should still be called, with the patient evaluated at a hospital, even if the symptoms have disappeared. Transient ischemic strokes are a warning sign of a full stroke occurring in the future, therefore, their occurrence must not be disregarded. 

Arms & legs

Deep vein thrombosis occurs when an abnormal clotting occurs in the deep veins of the arms and legs. This condition is more common in the legs. Symptoms include throbbing pain and swelling in one limb. The skin around the painful area may also be warm and red. While less immediately dangerous than thrombosis in the heart or brain, deep vein thrombosis should still be brought to the attention of a doctor as soon as possible. This is due to the potential for fragments of the clot to break off and block other blood vessels in the body, particularly in the lungs.

The lungs

Pulmonary embolism occurs when a blood clot breaks off from another area of the body to block the arteries transporting blood to the lungs (pulmonary arteries). The clot often originates from deep vein thrombosis in the legs, with deep vein thrombosis and pulmonary embolism jointly known as venous thromboembolism. Symptoms include chest pain, shortness of breath, and coughing up blood. These symptoms overlap with other cardiovascular and respiratory diseases, making diagnosis difficult. 

Reducing the risk of acquired thrombophilia

Although genetic thrombophilia cannot be prevented, lifestyle changes can reduce the risk of acquired thrombophilia. Thrombophilia often occurs in tandem with medical conditions, including obesity, high blood pressure, and high cholesterol, as well as atherosclerosis. These non-communicable diseases are often linked to the lack of a healthy lifestyle, including smoking, a poor diet, and prolonged periods of inactivity. Lifestyle changes that reduce the risk of the above diseases also reduce the risk of thrombophilia.

Preventing thrombosis

Thrombosis is a preventable and treatable condition – if managed properly, people with thrombophilia do not experience abnormal blood clotting. Drugs such as anticoagulants prevent blood clot formation, while thrombolytics dissolve blood clots if a clot has formed inside a blood vessel.¹ Lifestyle changes can also reduce the risk of thrombosis in people with thrombophilia. 

People with thrombophilia should avoid dehydration by drinking an adequate amount of fluid (6 to 8 cups per day). Dehydration causes blood to thicken and blood volume to decrease, the sodium concentration in blood increases, leading to the release of the hormone vasopressin. One of the effects of vasopressin is the narrowing of blood vessels, which increases blood pressure and the risk of thrombosis.⁵ 

Those with thrombophilia should also avoid being immobile for long periods. Immobility increases the risk of blood clotting in the legs, causing deep vein thrombosis. When participating in activities that involve prolonged immobility (such as long train or plane rides), wearing compression socks improves blood circulation and reduces the risk of thrombosis.

As mentioned above, medications that increase estrogen levels (such as contraceptive pills and hormone replacement therapy) may increase the risk of thrombosis. Doctors may advise patients with thrombophilia to avoid certain medications or to use alternative medications in these circumstances. At the same time, anticoagulant drugs prescribed to treat thrombophilia may lead to complications, such as internal bleeding due to the blood-thinning effect of the drug. Every situation is different for each patient; there is no universal solution to preventing thrombosis. However, with careful consideration and discussion with doctors, it is possible to minimise the risk of thrombosis and further complications.

Summary

People with thrombophilia are at a higher risk of thrombosis – an abnormal blood clotting which may lead to potentially life-threatening complications, including ischemic stroke, heart attack, deep vein thrombosis, and lung embolism. However, people with thrombophilia do not always experience thrombosis, particularly if risk factors are identified and managed early. Through lifestyle changes such as staying hydrated, maintaining a healthy diet, increasing mobility, and wearing compression socks, the risk of abnormal blood clotting can be reduced. As every person’s prognosis of thrombophilia is different, discussing the condition with doctors can help implement a suitable treatment plan to reduce the risk of blood clots.