Risk and Risk Factors Associated With Recurrent Venous Thromboembolism Following Surgery in Patients With History of Venous Thromboembolism

<h3>Importance</h3> The size of the risk of recurrent venous thromboembolism (VTE) after surgery in patients with a history of VTE is not well known. <h3>Objectives</h3> To estimate the risk of and to identify the factors associated with recurrent VTE in patients undergoing surgery who have a history of VTE. <h3>Design, Setting, and Participants</h3> This population-based, follow-up cohort study includes patients with VTE who participated in the Multiple Environment and Genetic Assessment (MEGA) study. Original data were collected from March 1999 to April 2010. Data analysis began in June 1999 and ended in April 2010. <h3>Exposures</h3> Surgery following a first VTE. <h3>Main Outcomes and Measurements</h3> Kaplan-Meier analyses were used to estimate cumulative incidences of recurrent VTE. Cox regression with a time-dependent covariate (surgery) was used to calculate the hazard ratio (HR) for developing recurrent VTE after surgery compared with no surgery. <h3>Results</h3> Overall, 3741 patients (mean [SD] age, 48.4 [12.8] years; 2020 [54.0%] women) with a history of VTE were included in the analysis, amounting to 18 899 person-years, with a median (interquartile range) follow-up of 5.7 (3.0-7.2) years. Of the 3741 patients, 580 (15.5%) underwent surgery and 601 (16.1%) developed a recurrent thrombotic event. The 1-month cumulative incidence of recurrent VTE for all surgery types was 2.1% (95% CI, 1.2%-3.6%), which increased to 3.3% (95% CI, 2.1%-5.1%) at 3 months and 4.6% (95% CI, 3.1%-6.6%) at 6 months. At 6 months, risk of recurrent VTE ranged from 2.3% to 9.3%, depending on surgery type. In addition to surgery type, factor V Leiden mutation (HR, 3.4; 95% CI, 1.6-7.4) and male sex (HR, 2.7; 95% CI, 1.3-5.8) were associated with increased risk of recurrent VTE. <h3>Conclusions and Relevance</h3> Surgery was associated with an increased risk of recurrent VTE in patients with a history of VTE; risk remained high for up to 6 months after the procedure. This study suggests that high-risk individuals may be identified based on surgery type, sex, and the presence of factor V Leiden mutation. These findings stress the need for revision of the current thromboprophylactic approach to prevent recurrence in these patients.