Therapy

• for six months for first PE with transient risk factors  ^a
• indefinitely for  
  • idiopathic cases ^a
  • recurrent venous thromboembolism ^a

Why?

• 6 months of oral anticoagulant therapy for a first episode of a DVT or PE leads to fewer recurrences of venous thromboembolism than 6 weeks of therapy without clearly increasing bleeding or mortality ^a .
• Indefinite oral anticoagulant therapy for a first idiopathic episode of a DVT or PE leads to fewer recurrences of venous thromboembolism than 3 months of therapy without clearly increasing bleeding or mortality ^a .
• Indefinite oral anticoagulant therapy for a second episode of a DVT or PE leads to fewer recurrent venous thromboembolism than 6 months of therapy without clearly increasing bleeding or mortality ^a .

Anticoagulation reduces recurrent and fatal pulmonary embolism

Patient	Treatment	Comparison	Outcome	CER	RRR (95% CI)	NNT (95% CI)
First PE or DVT a	anticoagulation for 6 months	anticoagulation for 6 weeks	recurrent VTE at 2 years	18%	48% (26% to 63%)	12 (8 to 24)
First idiopathic PE or DVT a	indefinite anticoagulation	anticoagulation for 3 months	recurrent VTE at 10 months	21%	94% (55% to 99%)	5 (4 to 10)
Second PE or DVT a	indefinite anticoagulation	anticoagulation for 6 months	recurrent VTE at 4 years	21%	88% (60% to 96%)	6 (4 to 10)