DEEP vein thrombosis (DVT) is clot formation (thrombus) or hardening of the blood in the venous system located in the deep surfaces of the body, that is, veins lying deep under the skin’s tissues, fat and muscles.

According to internist Dr Jomo James, veins are tubular structures that return blood to the heart, and while there are superficial veins just below the skin, there are also deeper ones that we should be concerned about.

“Thrombus formation can occur anywhere deep or superficial but is more common and dangerous in the deep veins. They occur mainly in the veins of the legs but can involve those of the arms as well,” he said.

Dr James said blood clots or thrombosis occur for mainly three reasons in general, and these include:

1. Damage to blood vessel wall, for example from trauma inflammation.

2. Poor blood flow or stagnation of blood leading to pooling, which can range from blockage of the vessel upstream from a tumour or growth to being sedentary; or prolonged inactivity, for instance a long trip, usually on a plane, or after a major surgery.

3. Tendency for one’s own blood to clot easily or abnormal clotting factors which could be inherited or acquired with certain conditions over time.

However, Dr James said in thrombus formation more than one of the above factors is likely the case.

He said women, particularly those of child-bearing age, have unique characteristics that place them at a greater risk for thrombus formation.

“This is more in doing with hormonal changes and reproductive physiology,” he said. These characteristics include:

1. Obesity

Dr James said this is a risk factor for thrombus formation as it is mainly related to sluggish blood flow and obesity is more common in women.

2. Hormone contraceptives

“Mostly high oestrogen oral contraceptive pills [OCP] increase two to fourfold the risk in thrombus formation. Albeit less so, progesterone-only OCP and injections or other forms of hormone contraceptive delivery also confer some increased risk in women for DVT. The main mechanism for thrombus formation is believed to be increased clotting factors,” Dr James said.

3. Hormone replacement therapy

The internist said hormone replacement therapy also confers an increased risk.

4. Breast cancer medication

Dr James said breast cancer medication, specifically Tamoxifen, is associated with a small risk.

5. Compression of the veins from pelvic organs

According to Dr James, compression of the veins from pelvic organs in women is common and leads to sluggish and stagnation of blood flow coming from the legs. “The most common cause is uterine fibroids. The enlarging uterus from pregnancy can also compress these veins and lead to thrombus formation by the same mechanism but this is rare,” he said.

6. Autoimmune diseases

The internist said these are more common in women. “An example is lupus, which increases the risk for clot formation through abnormal clotting factors and damage to blood vessel walls by way of inflammation,” he said.

Dr James added that unique to both genders are smoking, a sedentary lifestyle, prolonged travel, cancers, heart failure, and the inherited or acquired clotting abnormalities, to name a few.

The main complication from DVT is that the clot may break off and travel by the veins to the heart, which pumps it to the lung, which leads to pulmonary embolism (PE).

“PE is when the clot now lodges itself in the pulmonary vessels. It is dangerous and can be fatal if not treated promptly,” he said.

Dr James added that another common complication is venous insufficiency where the veins become permanently damaged in the affected limb. Symptoms of DVT include swelling, heaviness and pain in the affected limb.

“Any one-sided swelling over the norm to any limbs, particularly legs, should be investigated for DVT,” Dr James said. He said diagnosis is usually made by a simple doppler ultrasound of the leg or affected limb.

“In addition to confirming the diagnosis of DVT, a search for risk and causes should also be made as that will determine the duration of treatment and prevention measures,” he said.

“Treatment is by using blood thinners or clot busters depending on severity. Rarely is surgery used to remove a clot but it is also included in treatment options.”

Dr James added that the treatment for DVT has made leaps and bounds in the past decade and the options are wider and sometimes more convenient. He said the main goal of treatment is to prevent PE, but other goals include preventing the clot from enlarging and preventing new clots from forming.

He said women can reduce their risk of DVT by regular exercise during pregnancy, using low- dose contraception if necessary, and treatment for problematic fibroids. In addition, he said the universal risk factors such as smoking, obesity and sedentary lifestyles should be addressed.

“If you are taking long trips, it is recommended to walk periodically to keep blood flow in the veins going,” he said.