Target INR for mechanical valves

Valve position	Valve type	Examples	INR target in patients WITHOUT additional risk factors	INR target in patients WITH any of the following risk factors: Prior thromboembolism Atrial fibrillation Rheumatic mitral stenosis (any degree) LVEF <35%	Concurrent aspirin therapy?
Aortic or pulmonic	On-X valve		2.5 for first 3 months; thereafter 1.5 to 2.0	2.5	Yes, aspirin 75 to 100 mg orally once daily*
	Low-risk valves	Bileaflet valves Medtronic Hall tilting disc valve	2.5	3.0	Not routinely*
	High-risk valves	Tilting disc valves other than Medtronic Hall Ball-in-cage	3.0	3.5	Not routinely*
Mitral or tricuspid	Low-risk valves	Bileaflet valves Medtronic Hall tilting disc valve	3.0	3.0	Not routinely*
Mitral or tricuspid	High-risk valves	Tilting disc valves other than Medtronic Hall Ball-in-cage	3.5	3.5	Not routinely*

Patients with mechanical valves require anticoagulation with a VKA (eg, warfarin). The approach described here follows the convention in the 2020 American College of Cardiology/American Heart Association (ACC/AHA) and 2021 European Society of Cardiology (ESC) valve guidelines, which specify INR targets rather than ranges. The acceptable range extends to 0.5 INR units on each side of the target. The use of targets was deemed preferable to ranges because it is more likely to reduce the time the INRs are closer to the upper or lower limit of the range. For a patient with more than one mechanical valve, the highest applicable target INR is used.
Careful INR monitoring is essential. Frequent monitoring is required when establishing the VKA dose, when there is an intercurrent illness or a potentially interacting exposure (such as change in medication or diet), and when the INR is outside the target range. When the patient is on a stable maintenance VKA dose with established therapeutic INR level, the INR is assessed at least monthly in patients with mechanical valves (and at least twice per month in patients with an On-X aortic valve treated with a target INR of 1.5 to 2.0 plus low-dose aspirin).

INR: international normalized ratio; LVEF: left ventricular ejection fraction; VKA: vitamin K antagonist.
* Routine addition of low-dose aspirin is generally not required (except for patients with an On-X aortic valve). For patients with mechanical valves with a concurrent indication for antiplatelet therapy, a decision on whether to add antiplatelet therapy to anticoagulant therapy is based upon assessment of the estimated benefits (eg, reducing risk of coronary stent thrombosis) and risks (eg, bleeding) of such therapy. Refer to UpToDate content on coronary artery disease patients requiring combined anticoagulant and antiplatelet therapy.

Prepared with data from:

Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA guideline for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation 2021; 143:e72.
Vahanian A, Beyersdorf F, Praz F, et al. 2021 ESC/EACTS guidelines for the management of valvular heart disease. Eur Heart J 2021; ehab395.

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