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 There are two sets of blood vessels in the human body. The arteries which supply blood from the heart and the veins which bring back  blood. The veins of the lower limb are  divided into two groups-the superficial and deep. The deep venous system can at times get completely blocked by blood; this condition is called DVT [deep venous thrombosis].

DVT can develop because of two conditions

1. Disorders of blood clotting

2. Stagnation of blood as seen in a bedridden patient like after a major surgery, head injury or stroke. It can also be seen on sitting or standing for a long time like during a trans-Atlantic flight.

Complications of DVT

The mostly frequent complication of DVT is a condition called thrombotic syndrome. As mentioned earlier the lower limb has 2 sets of veins the superficial and the deep. The veins of the deep system has valves that maintain unidirectional flow to the heart. In DVT the vessels may recanalize over a period of time but but the valves of the veins get destroyed resulting in stagnation of blood in the deep venous system. Sometimes these veins do not recanalize at all and then flow through the deep system becomes grossly impaired. In both the situations the superficial venous system takes the blunt of the reduction in flow in the deep system and these veins become dilated. The leg become swollen, with discoloration and ulceration.

PTA syndrome can be debilitating since the patient may find it difficult to walk or stand for prolonged periods of time in addition the ulceration and skin changes make it extremely difficult to lead a normal life.

Treatment for PTS

The only way to prevent post thrombotic syndrome would be to ensure that these blocked veins are open at the earliest. Blood thinning agents like heparin and warfarin which is conventionally used have very poor results. Several studies have shown that the best way to open these blocked vessels is the use of a group of drugs called thrombolytics day are available in the market as urokinase , streptokinase and TPA.

For a long time this drug was given intravenously however, intravenous injection of this drug has a certain risks associated with bleeding from sites like the brain and intestine which can at times be fatal. Does came the concept of taking a catheter through a puncture into the segment of the vessel close to the knee joint and injecting the drug directly into the clot. This form of therapy is called regional thrombolysis.

Regional thrombolyzes if performed within 2 weeks of DVT can results recanalization in close to 80% of the patient's. It is also noticed that the valve function is preserved if  thrombolysis   if  performed within two weeks of DVT. Another significant advantage of regional thrombolysis is the inability to study the vessel after recanalization. This is important since the underlying vessels may have a narrow segment

 which can be rectified preventing further DVT

Complications

The complication of regional thrombolysis in DVT include pulmonary embolism which can be prevented by placing an IVC filter, this is usually performed if the thrombus extends into the inferior vena cava. Although regional as thrombolysis is safer than intravenous administration of the drug, it still continues to carry the risks of bleeding into the brain and intestine  which can still prove fatal.