Deep-vein thrombosis and pulmonary embolism

Abstract

Venous thromboembolism in this situation the embolism is detached from the thrombus (usually in the proximal veins of the thigh) and ends up obstructing the pulmonary arteries and therefore producing a pulmonary embolism (see above). Deep vein thrombosis (DVT) of the lower limb and its acute complication, pulmonary embolism (PE), are major causes of death and disability. In the general population, clinically recognised DVT and/or PE occurs in about 2 in 1000 persons each year. In the hospitalised population DVT and PE are much commoner. This is probably due to the contribution of acute injury, surgery or medical illness (which cause pooling of blood in the deep leg veins, within which activated clotting factors produce fibrin rich thrombi) (SIGN, 1995). A recent study in Sheffield (Thromboembolic Risk Factors (THRIFT) Consensus Group, 1992), found that 9 per cent of patients admitted to a general hospital died and that 10 per cent of these deaths (0.9 per cent of all admissions) were due to pulmonary embolism. This is approximately 77,000 deaths in 1992 (in 1995 it is estimated that the number of hospital deaths due to PE will have risen to 80,000; OHE, 1995). Clinical diagnosis The clinical diagnosis of DVT and PE has always been unreliable (Sharnoff, 1980), particularly with regard to physical symptoms and signs. Some of the physical symptoms and signs of DVT include pain and tenderness in the calf muscles, swelling of the calf or thigh and palpation of vein cords in the leg and thigh muscles, increase in temperature and skin discoloration (cyanosis). Objective tests have shown that the clinical physical signs are only 50 per cent or less accurate, with a frequent false-positive diagnosis (Weinmann and Salzman, 1994). Not only are some of these tests of limited sensitivity but a major difficulty is that other conditions besides deep vein thrombosis can cause a painful, swollen leg. In a study of 87 consecutive patients with clinically suspected deep vein thrombosis, who had a normal phlebogram (see Box 1), it was found that only 34 actually had a DVT. Of the remainder, 37 had a musculoskeletal cause, 12 had impaired venous or lymphatic flow, and 4 had popliteal cysts (Baker's cysts) (Hull et al, 1981). Therefore a diagnosis suspected on clinical grounds must be confirmed by a sensitive diagnostic test. The diagnosis of pulmonary embolism is also frequently inaccurate both clinically and radiographically. The most common clinical signs are dramatic, sudden collapse, air hunger, cyanosis and shock. Less common are pleuritic chest pain, apprehension, cough,