Balancing risks and benefits of extended anticoagulant therapy for idiopathic venous thrombosis

Management of deep vein thrombosis to reduce the incidence of post-thrombotic syndrome

The post-thrombotic syndrome (PTS) is the major chronic sequel of deep vein thrombosis (DVT) of the leg, and is a major socioeconomic challenge. In addition to systematic prophylaxis of DVT in hospitalized patients, effective management of DVT is important to reduce the incidence of PTS. Thrombolysis and thrombectomy are not indicated routinely. Optimal anticoagulation, usually with heparins initially and then with oral warfarin, is important to prevent recurrent DVT, which is a major risk factor for PTS. Following a routine three-month period of anticoagulation, patients with proximal idiopathic DVT should be individually assessed for the benefits and risks of continued oral anticoagulation, including patient preferences. Risk factors for recurrent DVT include active cancer, pregnancy, continued use of oral oestrogens, male sex, obesity, recurrent thrombosis, established PTS, permanent inferior vena caval filters, residual DVT, high fibrin d-dimer and other thrombophilias. Early walking, continued high levels of physical activity and wearing compression stockings for up to two years may also reduce the risk of PTS.

Procoagulant activity, but not number, of microparticles increases with age and in individuals after a single venous thromboembolism

The Calibrated Automated Thrombogram (CAT), a plate-based assay that measures thrombin generation and inhibition in plasma samples, is modified to measure the procoagulant activity of phospholipid associated with plasma microparticles (MP). The assay uses a tissue factor trigger without addition of 4 μM exogenous phospholipid (PL) used in the standard CAT. Calibrated with 4:1 posphatidylcholine- phosphatidylserine (PCPS) liposomes, the assay defines a median of 40 nM procoagulant phospholipid (PPL) equivalents in plasma containing MPs from 50 normal donors, with a range from 20 - 200 nM. Like the standard CAT, the modified assay detected no difference in plasma from 36 individuals with a history of a single episode of venous thromboembolism. However the male cases had double the PPL activity, as measured by rate of thrombin generation, of females; and there was a significant correlation among cases of increased thrombin generation with age. In contrast, there were no gender disparities or age correlations among control plasmas. The findings suggest that procoagulant activity of plasma microparticles, facilitated by a simplified, one-stage plate-based assay, offer a promising avenue of investigation of mechanisms and management of venous thromboembolic disorders.

Recurrent venous thromboembolism after surgery-provoked versus unprovoked thromboembolism

SUMMARY BACKGROUND

The incidence of recurrent venous thromboembolism (VTE) varies depending on the nature of the initial provoking risk factor(s).

OBJECTIVES

To compare the incidence and time course of recurrent VTE after unprovoked VTE vs. VTE provoked by nine different types of surgery.

METHODS

Retrospective analysis of linked California hospital and emergency department discharge records. Between 1997 and 2007, all surgery-provoked VTE cases had a first-time VTE event diagnosed within 60 days after undergoing a major operation. The incidence of recurrent VTE was compared during specified follow-up periods by matching each surgery-provoked case with three unprovoked cases based on age, race, gender, VTE event, calendar year and co-morbidity.

RESULTS

The 4-year Kaplan-Meier cumulative incidence of recurrent VTE was 14.7% (95%CI: 14.2-15.1) in the matched unprovoked VTE group vs. 7.6% (CI: 7.0-8.2) in 11 797 patients with surgery-provoked VTE (P < 0.001). The overall risk reduction was 48%, which ranged from 64% lower risk (P < 0.001) after coronary bypass surgery to 25% lower risk (P = 0.06) after disc surgery. The risk of recurrent VTE 1-5 years after the index event was significantly lower in the surgery group (HR = 0.47, CI: 0.41-0.53). Within the surgery-provoked group, the risk of recurrent VTE was similar in men and women (HR = 1.0, CI: 0.8-1.3).

CONCLUSIONS

The risk of recurrent VTE after surgery-provoked VTE was approximately 50% lower than after unprovoked VTE, confirming the view that provoked VTE is associated with a lower risk of recurrent VTE. However, there was appreciable heterogeneity in the relative risk of recurrent VTE associated with different operations.