Venous thromboembolism. Epidemiological and clinical aspects of deep vein thrombosis and pulmonary embolism

Abstract

Venous thromboembolism including deep vein thrombosis (DVT) and pulmonary embolism (PE) is the third most common cardiovascular disease after ischemic heart disease and stroke and is contributing to escalating health care costs in the industrialised part of the world. Most epidemiological data derives from hospital studies and knowledge of the incidence and risk factors of the disease in the general population is limited.Within the framework of a general population study, "The Study of Men Born in 1913", 855 men were followed prospectively from the age of 50 to the age of 80. Four men had suffered a venous thromboembolic event (VTE) before the age of 50 and another 65 men had their first VTE during the 30-year follow-up period. The cumulative incidence of venous thromboembolism was 10.7% by the age of 80 years. The incidence rate of a first DVT was 1.4 per 1,000 observation-years. The corresponding incidence rates were 0.7 for non-fatal PE, and 1.1 for fatal PE. Waist circumference (p=0.004) and smoking (p=0.022) at baseline predicted a venous thromboembolic event in multivariate survival analysis. Men in the highest decile of waist circumference (= 100 cm) had an adjusted relative risk of 3.92 (95% CI: 2.10-7.29, p<0.001) compared with men with a waist circumference of less than 100 cm. For men who smoked 15 g of tobacco (e.g. 15 cigarettes) a day or more, the adjusted relative risk was 2.82 (95% CI: 1.30-6.13, p=0.009) compared with non-smokers. Reducing obesity and smoking in the population may have a preventive effect on VTE.Plasma from 382 participants in "The Study of Men Born in 1913" was stored in 1988 (at 75 years of age) for subsequent analysis of APC resistance. Twenty-five men (6.5%) had a low APC ratio indicating hereditary APC resistance. The incidence of venous thromboembolism did not differ between men with or without APC resistance, either retrospectively or during follow-up. Only two of these men experienced a DVT before the age of 80 and there was no case of PE among these men.In a clinical study, we followed 738 consecutive patients with an objectively verified symptomatic deep vein thrombosis for 3.7-8.8 years. The five-year cumulative incidence of recurrent venous thromboembolic events was 21.5% (95% CI: 17.7-25.4) after a first DVT and 27.9% (95% CI: 19.7-36.1) after a second DVT. Proximal DVT (RR:2.40, 95% CI:1.48-3.88, p<0.001), cancer (RR:1.97, 95% CI:1.20-3.23, p<0.001) and a history of a prior venous thromboembolism (RR:1.71, 95% CI:1.16-2.52, p<0.01) independently predicted an increased risk of recurrent events in multivariate survival analysis. Postoperative DVT (RR: 0.27, 95% CI: 0.13-0.55, p<0.001) and a long duration of oral anticoagulation therapy (RR: 0.95, 95% CI: 0.92-0.98, p<0.01) involved a smaller risk of recurrent events.In order to study the diagnostic usefulness of various markers of blood coagulation or fibrinolysis, we compared laboratory testing with phlebography findings in 105 consecutive patients with a clinically suspected DVT at an emergency unit. Plasma D-dimer had the best negative predictive value. One latex D-dimer test was found to be as sensitive as a more costly and time-consuming ELISA D-dimer test. The negative predictive value was 93% and the positive predictive value 71% compared with phlebography. In spite of a relatively high negative predictive value, the usefulness of a D-dimer test in clinical practice is controversial.