Understanding Risk Factors Involved in Developing a Second Blood Clot.

patients diagnosed with idiopathic blood clots

Inclusion Criteria:

1. Objectively proven (as previously described (8)) proximal idiopathic deep vein thrombosis or pulmonary embolism. Idiopathic will be defined as VTE occurring in the absence of fracture, plaster cast, immobilization greater than 3 days or a general anesthetic in the last three months prior to VTE diagnosis; a known deficiency of antithrombin, protein C or protein S; and malignancy in the last five years
2. Patients treated initially with a minimum of five days of heparin or low molecular weight heparin and oral anticoagulants with a target intensity of 2.0 - 3.0 with no recurrence in the subsequent six months.
3. Patients currently on oral anticoagulants

Exclusion Criteria:

1. Recurrent idiopathic VTE (i.e. ≥ 2 previous idiopathic VTE). Previous secondary VTE is not an exclusion criterion;
2. Age <18;
3. Known deficiency of proteins S, protein C or antithrombin;
4. Known, persistently positive anticardiolipin antibodies (titers > 30U/ml);
5. Known, persistently positive lupus anticoagulant;
6. Combined thrombophilic defects (e.g. homozygous for FVL or PGM, or compound heterozygous for FVL and PGM);
7. Refusal of informed consent.