Thrombosis

What is thrombosis?

When you are cut anywhere on the body, the body's mechanisms rapidly act to prevent one from bleeding to death. Components of the blood are activated and form a jelly- like substance which plugs off the blood vessel. This jelly like substance is called a blood clot. When the blood clots continue to accumulate and get solidified (hardened), it is known as a thrombus. In the human body, mechanisms exist to ensure that unnecessary blood clots will not occur. However, occasionally the system goes awry and blood clots start to form – which eventually result in a thrombus.

Where do thrombi usually form?

Thrombi may form in either the arteries (vessels which carry oxygen rich blood) or in the veins (vessels which carry deoxygenated blood back to the lungs). When the artery is blocked by a thrombus, the organ or tissue supplied by the vessel will not get adequate blood or oxygen. When a vein is blocked with a thrombus, the blood starts to collect and occasionally the thrombus may break off and migrate to the lungs.

What happens to a venous thrombus?

The majority of thrombi in the veins are usually broken down by the body's system. However, occasionally the thrombus can break off and migrate to the lungs. In the lungs, the thrombi can partially or completely block the lungs (and prevent the blood from getting oxygenated). If the thrombus is small, the patient may recover after medical therapy. If the thrombus is large, the individual can die.

Do all veins develop a thrombus?

Yes, all veins can develop a thrombus. However, there are two categories of veins- superficial and deep. Thrombus in the superficial veins is of no big medical consequence. However, thrombus in the deep veins (also known as Deep Vein Thrombosis) is a serious condition with potentially fatal consequences if not recognized.

What happens to an arterial thrombus?

In general, when the artery is blocked by a thrombus, the tissue which is supplied by that vessel will no longer receive enough oxygen or blood. The tissue may start to die (ischemia) after a few hours. This is classically seen in a heart attack or a stroke. Occasionally, thrombus in an artery may close off the blood supply to the legs, arms or eyes. Unlike venous thrombi, most arterial thrombus will present with acute symptoms and the diagnosis is usually made more rapidly.

What are risk factors for venous thrombosis?

The following can increase the risk of venous thrombosis:

- trauma to the legs

- fractures of the legs (esp. hips, knee)

- prolonged stay in bed after surgery

- bed ridden after a stroke

- taking the birth control pill

- weight gain

- certain blood disorders may predispose you to clots

- cancer

- pregnancy

What are risk factors for arterial thrombosis?

- heart attacks

- blood disorders

- atherosclerotic disease of blood vessels

- injury to the blood vessels

- trauma

- inherited blood disorders

- infections of the heart (endocarditis)

What are the symptoms of venous thrombosis?

The symptoms of a venous thrombosis are dependent on the size of the thrombus and the number of veins involved. Not all individuals have symptoms. In general, the classic symptoms of venous thrombosis may include:

- swelling of the arm or leg

- pain around the calf or arm

- redness around the calf

- low grade fever

- at least 30-40% will have no symptoms

What are the symptoms of arterial thrombosis?

Because arteries supply blood and oxygen for survival of many organs, arterial thrombosis is usually acute and the symptoms are more pronounced. Most individuals will have the following symptoms:

- pain

- loss of pulses

- purple leg or arm

- paralysis

- Abnormal sensations in the leg or arm (tingling, numbness). These symptoms occur when the nerves start to die off due to the lack of oxygen

- Stroke

- Heart attack

How is thrombosis diagnosed?

Whether it is arterial or venous thrombus, you will always be thoroughly examined at the first presentation. Basic blood work will done to ensure that all the blood parameters are within normal limits. Following the blood work, your physician may order:

Ultrasound: This is usually the first test to determine the presence of a thrombosis in the legs, arms and neck area. It is a painless and a sensitive test. It is somewhat operator dependent but relatively cheap.

MRI: When thrombosis is suspected but Ultrasound fails to detect it, MRI is an excellent method. MRI can image the entire body rapidly and does not involve the use of radiation but is more expensive.

ECHO: When it is suspected that there is a heart infection (endocarditis) which is throwing off blood clots, an ECHO is an excellent diagnostic test. The test is painless and uses ultrasound to look at the heart and its valves.

Venogram: In the old days, venogram was used to look for venous thrombus. Today, the technique is rarely used because of the availability of ultrasound, CT scan and MRI.

Angiogram: This technique can detect arterial thrombus anywhere in the body. It requires the injection of a dye and exposure to radiation. For some parts of the body, it still remains the best test to detect thrombus.

CT scan: When a thrombus is suspected in the lungs, CT is an excellent imaging tool. It requires the use of a dye and exposure to radiation.

What is general treatment of thrombosis?

Specific treatment for thrombosis is dependent on the following factors:

- your age (must be able to withstand surgery)

- overall health

- medical history (any other medical conditions like diabetes, heart failure)

- where the thrombus is located

- tolerance to blood thinning medications

- availability of hospital facilities and physician experience

- your preference

What is specific treatment of thrombosis?

Whether it is venous or arterial thrombosis, some type of therapy is required. In general, the following are used to treat thrombosis:

Blood thinning medications: Blood thinners are a must for all thrombosis and include medications like heparin, warfarin and low molecular weight heparins. These mediations do not dissolve the clot but stabilize it to prevent it from migrating.

Thrombectomy: Sometimes the thrombus blocks the artery supplying blood to the leg. In such cases, specially designed catheters (balloons) can be used to suck out or remove these thrombi. Improvement is immediate but this is a surgical procedure.

Thrombolytics: In some individuals, special medications (thrombolytics) can be used to dissolve the clot. There are specific guidelines for the use of these chemicals and they carry a high risk of bleeding.

Surgery: In rare cases, surgery may be required to remove the thrombus from the lungs (pulmonary thrombectomy). This is a major undertaking and only done as a life saving procedure.

How can one prevent thrombosis?

Prevention for venous thrombosis should include the following:

- stay active

- exercise regularly

- do not stand for long periods

- when resting, elevate your legs

- when flying or driving for long distances, wear compression stockings

- control your weight

To prevent arterial thrombosis, one should:

- stop smoking

- control your diabetes (especially your blood sugar)

- eat health low fat diet

- control your blood pressure

- watch your cholesterol

- if you are over 50 years, an aspirin a day is highly recommended