Risk of recurrence of thromboembolism

Hansson et al (1) undertook a cohort study of 738 patients with deep vein thrombosis (DVT) confirmed by colour duplex ultrasonography or phlebography who had been discharged from the hospital and survived to 1 month. Follow-up varied from 3.7 to 8.8 years.

Three factors were identified that increased the risk for recurrent venous thromboembolism (VTE):

• cancer (relative risk (RR) 2.30, 95% CI 1.55-3.42)
• having had a proximal DVT (RR 2.21, CI 1.43-3.41)
• history of VTE (RR 1.71, CI 1.16-2.52)

Two factors were associated with a decreased risk for recurrent VTE:

• DVT after surgery (RR 0.27, CI 0.13-0.55)
• long-term anticoagulant treatment (RR 0.95, CI 0.92-0.98)

A review suggests that overall more than 20% of DVTs recur within 5 years - risk of this is higher if there are underlying risk factors (2)

More recent studies provides evidence that, after a first episode of thromboembolism, men were at a greater risk of a recurrent episode than women (3,4):

• men seem to have a 50% higher risk than women of recurrent venous thromboembolism after stopping anticoagulant treatment (4)

Risk of fatal pulmonary embolism following discontinuing anticoagulant therapy for venous thromboembolism (5):

• risk for fatal PE is 0.19 to 0.49 events per 100 person-years for patients who have finished a course of anticoagulant therapy for a first episode of symptomatic VTE. The case-fatality rate for death from recurrent PE is 4% to 9%
• findings are less pertinent to patients with active cancer, permanent immobility, or high-risk thrombophilia
• study period was for 4.5 years after discontinuing anticoagulant therapy

References:

1. Hansson PO et al. Recurrent venous thromboembolism after deep vein thrombosis. Incidence and risk factors. Arch Intern Med 2000;160: 769-74.
2. MeReC Bulletin (2003); 13(4):13-16.
3. Kyrle PA et al. The risk of recurrent venous thromboembolism in men and women. NEJM 2004;350:2558-63
4. McCrae S et al.Effect of patient's sex on risk of recurrent venous thromboembolism: a meta-analysis. Lancet. 2006 Jul 29;368(9533):371-8.
5. Douketis JD et al. The risk for fatal pulmonary embolism after discontinuing anticoagulant therapy for venous thromboembolism. Ann Intern Med. 2007 Dec 4;147(11):766-74