Prevention of Recurrent Venous Thromboembolism in Patients With Low Circulating Levels of Antithrombin. Extended Anticoagulation vs 12-Month Oral Anticoagulation

Study population: subjects with a recent (<3 months) first VTE event will be enrolled for a long-term follow-up. Clinical visits will be performed every 4-6 months (average).

In each case, objective diagnosis has to be achieved by compression ultrasonography, the diagnosis being based on the lack of compressibility of one or more venous segments. PE has to be documented by ventilation/perfusion lung scanning or by spiral computed tomography (CT).

For each subject, information about pregnancy, active malignancy, recent (<3 mo) surgery or trauma, fracture, immobilization, acute medical illness, use of oral contraceptives, long-distance travel, personal or family history of arterial and/or venous thrombosis or repeated birth losses will be collected. In the presence of at least one of the previous risk factors, VTE will be defined as secondary otherwise idiopathic. Further information, collected from the whole population by a trained staff, were the following: gender, age, weight, height, body mass index (BMI), waist circumference, personal history of symptomatic atherosclerosis (i.e. ischemic stroke, transient ischemic attack, acute myocardial infarction, angina, intermittent claudication), arterial hypertension, use of antihypertensive drugs, diabetes mellitus, use of antidiabetic drugs, hyperlipidemia, use of statins, smoking habit (use of cigarettes/d), current use of heparin, use of oral anticoagulant (how long) or of antiplatelet drugs (how long), chronic consumption of other drugs.

All these information will be collected by a trained staff on admission and during follow-up visits (every 4-6 months).

Exclusion criteria: missing data during the follow-up; contraindications to or lack of compliance to oral anticoagulation (OAT), lack of informed consent; history of previous VTE event; indication for continuous oral anticoagulation (e.g., an artificial heart valve or chronic atrial fibrillation); events occurring during pregnancy, malignancy, puerperium, oral contraceptive intake, hormone replacement therapy; deficiencies of Prot. C and Prot S or combined inhibitor deficiencies.