What is thrombosis?
Thrombosis is a process by which there is clotting of the blood in a part of the circulatory system. This causes a partial or total obstruction thus preventing blood from flowing normally through the circulatory system. This clot is known as a thrombus.
What is Deep Vein Thrombosis(DVT)?
A blood clot (thrombus) in the deep venous system is known as DVT. These clots are formed in the deep veins which are a part of the circulatory system that helps bring deoxygenated blood back to the heart. These veins have one-way valves that function to transport blood from various parts of the body to the heart as shown in Fig 1.
Which body part can be affected with DVT?
There is a greater risk of developing DVT in your lower limbs than upper body as the deep lower limb veins work harder to carry blood back to the heart with forces from the body weight and gravity acting on them at the same time. In addition, if there are other factors that increases the pressure exerted on the valves in the deep lower limb veins, there are more chances of blood collecting within the veins thus making the lower limbs deep veins more susceptible to DVT.
Why is DVT dangerous?
There is a risk of a partial or complete detachment of this thrombus formed in the deep veins. This allows the thrombus to move with the blood flow and block other blood vessels. This process is called as venous thromboembolism.
As shown in Fig 1, the thrombus blocks the blood vessel and cuts off the circulation to a particular body part or organ. This will lead to a lack of oxygen to the tissue (ischemia) and a loss of tissue function. The clot can also reach other blood vessels that supply the vital organs of the body, putting the body at a dangerous risk of stroke, lung, heart problems and post-thrombotic syndrome (PTS).
Post-thrombotic syndrome is a chronic(long-term) problem that occurs with DVT and involves chronic leg pain, swelling, redness, and ulcers (sores).
How does a thrombus form in the deep veins?
Blood clotting is the transformation of liquid blood into a semi-solid gel. The blood has a protein called fibrin. Fibrin is usually in its inactive state but when tissues or blood vessels are damaged, it becomes active. This process is called coagulation. The main reason of thrombus formation can be explained by the Virchow’s triad as shown in fig 2.
Conditions of prolonged bed rest or immobility which could be lifestyle-related or due to other reasons may cause stasis of blood within the veins that may lead to clot formation. Also, if there is an imbalance of the coagulation and anti-coagulation factors in the blood which may be caused by an injury or acute/chronic inflammation to the blood vessel walls may cause blood clot formation.
Who is at risk of developing DVT?
- Anyone with vein trauma due to broken hip or leg fractures during accidents.
- Long periods of air travel coupled with lack of movement in sitting position can cause excessive swelling in the legs and stagnation of blood flow leading to clot formation.
- Bed bound individuals post-surgery, muscular paralysis from a spinal cord injury, pregnancy or having recently given birth, especially by C-section, causing swelling and lack of calf muscle strength that impair blood circulation in the legs.
- People with inherited blood clotting disorder.
- People who have cancer as tumors shed particles that contain procoagulant activity.
- Smoking affects blood circulation and stiffens the blood vessel wall making a smoker at higher risk of DVT.
- Side-effects with the use of hormone therapy, including that used for postmenopausal symptoms among women.
- Individuals with varicose veins, which are swollen, twisted and painful may develop clots.
- People with a history of heart attack, stroke or congestive heart failure have high levels of cholesterol in the blood that lead to inflammation and possibly clot formation.
Signs and Symptoms of DVT
- Pain, swelling and tenderness in one of your legs (usually your calf)
- Affected area can be very painful and heavy.
- Warm skin in the area of the clot.
- Redness of the skin, particularly at the back of your leg below the knee.
How is DVT diagnosed?
A physical examination may not be enough as there may be individuals with no possible signs of DVT. Diagnostic tests will be necessary to confirm the condition.
- Doppler ultrasound scan: A clot may be visible in the image. Sometimes a series of ultrasounds are done over several days to determine whether a blood clot is growing or to detect any formation or movement of a clot.
- Blood test: An elevated level of a clot-dissolving substance called D dimer will be found in the blood.
- Venography. A dye (contrast agent) is injected into a large vein in your foot or ankle. An X-ray procedure is then undertaken that creates an image of the veins in your legs and feet, to look for clots.
- CT or MRI scans. Both computerized tomography (CT) scan and magnetic resonance imaging (MRI) can provide visual images of your veins and may detect any clot formed.
When to seek medical care?
- If you get swelling, redness, and pain in your leg, it may indicate a blood clot and immediate medical attention should be given. Sometimes there may not be any signs or symptoms or these symptoms could be due to other inflammatory condition or infection, therefore, it is difficult to make the diagnosis without seeking medical advice.
- If there is associated pain in the chest or breathlessness further concern exists that you may be at risk of a pulmonary embolus. This could be a potential danger hence if you are at risk its best to discuss with your doctor about taking medications for preventing clot formation.
How to prevent DVT?
- Compression stockings for bed bound individuals.
- Early ambulation Post-surgery – getting the individual out of bed walking to allow good circulation of blood. If not possible, use a continuous passive motion (CPM).
- Low dose of anti-coagulants can also be prescribed by the doctor.
- During long flights, it is recommended to move frequently and/or use compression stockings.
- Ankle exercises can help pump the blood from the legs upwards to the heart.
- Lifestyle modifications – smoking cessation and increased exercise.
If in doubt or experiencing any of the symptoms, always seek medical advice immediately. When detected early, it’s much easier to deal with.