Deep Venous Thrombosis

Unlike arterial thrombosis, venous thrombosis may often occur in normal vessels. Risk factors are stasis and hypercoagulability

The vast majority of venous thrombosis occurs in the deep veins of the leg, with point of origin around the valves as ‘red thrombi’ made up of red blood cells and fibrin. This accumulates forming a thrombus of fibrin and platelets and is at high risk of embolisation. Chronic venous obstruction in the deep veins of the leg may results in a potentially permanently swollen limb and may develop into ulceration (post phlebitc syndrome). Risk factors may be divided into ‘patient related’ or ‘disease/surgical procedure’ and are summarised in the table.

Patient Factor

Disease/Surgical Procedure

Age

Trauma or surgery e.g. pelvis, hip, lower limb

Obesity

Malignancy

Varicose veins

Cardiac failure

Immobility (bed rest > 4 days)

Recent myocardial infarction

Pregnancy and Puerperium

Infection

High doses of oestrogens

Inflammatory bowel disease

Previous deep vein thrombosis or pulmonary embolism

Nephrotic syndrome

Thrombophilia

Polycythaemia, thrombocythaemia

 

Paroxysmal nocturnal haemoglobinuria

 

Sickle cell anaemia

 

Homocystinuria

(adapted from Chapter 6 Diseases of the Blood in Kumar and Clark (ed) Clinical Medicine 2nd edition W.B. Saunders 1994).

Pulmonary embolism (PE) and deep vein thrombosis (DVT) are collectively known as venous thrombo-embolism (VTE) and are important causes of both death and disability (28-31) The clinical impact of VTE is most severe in hospitalised patients with more than 50% of cases of VTE occurring during hospitalisation (32;33). In view of the large population at risk and the scope of the problem, numerous medical and governmental organisations have made VTE prevention a priority in the care of hospitalised patients (reviewed (34)).

Anti-coagulation is the mainstay of both prophylaxis and treatment of VTE. However anticoagulation is contraindicated in some at risk patient groups such as those undergoing complex surgery, acute or recent bleeding, haemorrhagic stroke, advanced liver disease or severe trauma. As an alternative to anticoagulation in these high risk patients, a number of organisations recommend the use of devices that interrupt the inferior vena cava (IVC) (35-37). In patients with a short term indication for IVC filters, retrievable devices may be used. The development of filters which may be placed and removed when no longer indicated was a key contribution to use of IVC filters becoming more widespread (38-40).