Indications

Therapeutic range	INR
Venous thromboembolism b	2.0 - 3.0
Venous thromboembolism with INR 2.0 - 3.0 d	3.0 - 4.5
Atrial fibrillation b	2.0 - 3.0
Biological heart valves a	2.0 - 3.0
Mechanical heart valves c	3.0 - 4.5

Why?

• A therapeutic range of 2.0 to 3.0 for first or recurrent episodes of DVT or PE is effective. ^b
• Patients with AF on warfarin are at increased risk for a stroke, TIA or a major bleed if their INR 4.0 or more. ^b  
• Patients with mechanical heart valves on warfarin have the fewest thromboembolic events or major bleeds when their INR is between 2.5 and 4.9. ^c
• Patients with biological heart valves have fewer major bleeds with an INR 2.0 to 2.25 and no clear increase in embolic than with an INR 2.5 to 4.0. ^a

Biological heart valves: a lower INR reduces the risk of major bleeding

Patient	Treatment	Comparison	Outcome	CER	RRR (95% CI)	NNT (95% CI)
biological heart valve a	INR 2.0  - 2.25	INR 2.5  - 4.0	major bleed at 3 months	4.6%	100%	22 (12 to 150)