The post-thrombotic syndrome consists of clinical features following thrombosis of deep venous veins of the limb (DVT). Patterns of post-thrombotic changes remain difficult to predict and once established, difficult to contain and reverse. Due to increased obesity and decreased physical activity this intent is increasing in number.
The course of the disease can be divided into an acute phase with a duration of about 7 to 10 days, the sub-acute phase following thrombosis lasting from the second to the fourth week and the phase of the post-thrombotic syndrome which will generally appear 10 to 15 years after the first event.
Following a thrombotic event of the extremity, 3 clinical stages can be observed which may be followed by intervening quiescent intervals.
Stage I, or the early phase, is characterized by the residual obstructive process following acute venous occlusion. This can be manifested by either a bursting type of pain (venous claudication) or oedema of the leg. A thrombotic process can involve the calf veins, thigh veins, pelvic veins, or any combination of the three.
During the healing process following DVT the occluded vein will go through a process of recanalization and collateralization. Concomitant with the presence of blood clot, fibrinolytic factors are then activated which will dissolve the thrombus to a certain extent after which blood flow can be re-established.
The extent of venous recanalization can be quantified radiological. In 35.5% of the patients there is complete recanalization, in 53.4% partial and in 11.1% no recanalization. At nearly all sites of venous occlusion collaterals generally can be found.
A hemodynamically relevant occlusion causes an increase in venous pressure which increase as the damaged valves loses more of their function as the vein distends. Doppler ultrasound examination shows an absence of respiratory modulation as well as a high-frequency continuous signal, which disappears as soon as collateral function is optimal.
Specific clinical syndromes develop depending on the venous pump system involved. The venous pump system consists of the calf muscle pump and the thigh pump. These serve to propel blood upward. Involvement of any one or more of the 3 in the thrombotic processes can result in a relative obstruction with a specific pattern of clinical symptoms.
Optimally, the venous thrombotic process should be treated during this early phase to prevent the subsequent events, which may render the process irreversible. The second stage of the post-thrombotic syndrome consists of the development of fat sclerosis (lipodermatosclerosis). At this stage, the process becomes progressively irreversible as the extravasation of fibrin into the interstitial space results in progressive fibrosis and sclerosis. This results in damage to the skin and subcutaneous tissues, which render the process irreversible. Specific treatment, while still introducible at this stage, can halt the progress of the syndrome, but rarely results in complete reversal.