Long-term Surveillance of Patients With Venous Thromboembolism: a Nationwide Prospective Cohort Study

This observational study aims to establish a prospective nationwide cohort of venous thromboembolism. The main questions it mains to answer are: * Which patients with venous thromboembolism should accept long-term anticoagulation therapy? * Mechanism and prognosis of venous thromboembolism. Participants will receive yearly follow-ups through telephone, hospitalization, or outpatient care.