Recurrent deep vein thrombosis: long-term incidence and natural history.

Objective: To determine the long-term incidence, risk factors, and associated morbidity and mortality of recurrent deep vein thrombosis (DVT).
Summary Background Data: Few studies have examined the long-term natural history and impact of recurrent DVT.
Methods: We conducted a prospective observational study that followed 153 consecutive patients with an acute first episode of DVT. Clinical examination and ultrasound were performed serially for at least 5 years. Location and extent of the initial DVT, recurrence, pulmonary embolism, cause of mortality, signs and symptoms of post thrombotic syndrome (PTS), and the risk factors were recorded.
Results: The incidence of recurrence at 5 years was 26.1%. Patients with both proximal and distal DVT had a higher recurrence rate than proximal (17/48 35% vs. 12/49, 24%, P = 0.27) or calf alone (11/56, 20%, P = 0.08). Unprovoked DVT and age >65 years were associated with higher recurrence rates (P < 0.001; relative risk [RR]: 2.9, 95% confidence interval [CI]: 1.5-5.7) and (P = 0.025; RR: 1.5, 95% CI: 1-2.3), respectively. Thrombophilia was not associated with increased risk of recurrence (P = 0.21). Patients with DVT due to surgery or trauma had a lower recurrence (P < 0.001). Ipsilateral recurrence was associated with increased severity of PTS (P < 0.001; RR: 1.6, 95% CI: 1.4-2.2). PE occurred 47 times, 12 (25%) of which were fatal events.
Conclusions: Factors associated with a higher rate of recurrence included unprovoked DVT and age >65. Elevated thrombus burden had a trend towards higher risk. Patients with surgery and trauma had low recurrence rates. Ipsilateral recurrence was strongly associated with PTS. PE occurred frequently and was a common cause of death.