Blood Thinner (Coumadin) Use and INR Monitoring After Valve Surgery

For our patients who have received a mechanical valve, lifelong, uninterrupted blood thinner monitoring is of vital importance. In this article I will explain the use of coumadin (warfarin) and INR monitoring.

Why Is Coumadin (Warfarin) Used?

The artificial surface of a mechanical valve can trigger the body’s clotting system; a clot forming on the valve can obstruct the valve’s movement, or break off and travel to the brain, causing a stroke. Warfarin slows the production of certain clotting factors made in the liver, thereby increasing the fluidity of the blood in a controlled way and substantially reducing this risk.

What Is the INR Test? What Should the Target Values Be?

INR (International Normalised Ratio) is a blood test that shows how quickly the blood clots; we use this test to monitor whether the warfarin dose is correctly adjusted. Current guidelines generally recommend a target INR of 2.5 (range 2.0-3.0) for a mechanical aortic valve, and 3.0 (range 2.5-3.5) for patients with a mechanical mitral valve or additional risk factors. If the INR is too low the risk of clotting increases, and if it is too high the risk of bleeding increases; for this reason regular checks and dose adjustment are necessary.

Nutrition While Taking Blood Thinners: The Leafy Greens Diet

Dark green leafy vegetables (such as spinach, broccoli and lettuce) contain high amounts of vitamin K; vitamin K can weaken the effect of warfarin. We do not recommend cutting out these vegetables completely, but rather keeping your intake consistent from week to week; sudden and large changes (for example eating no greens at all one week and a great deal the next) can cause fluctuations in your INR value.

Frequently Asked Questions

How often should I have my INR checked? Usually every 4-6 weeks once the dose is stable; more frequent checks are needed when the dose is changed.

Can I adjust my warfarin dose myself? No; the dose must always be adjusted according to the INR result, under a doctor’s supervision.

Can newer-generation blood thinners be used instead of warfarin? No; newer-generation oral anticoagulants (DOACs) have been shown not to be safe in patients with mechanical valves, and warfarin is the standard treatment in this patient group.

Conclusion

After a mechanical valve, warfarin use and regular INR monitoring are indispensable conditions for the valve to work safely. Regular monitoring of the dose and consistent eating habits directly affect the safety of this treatment.

You can book an appointment for anything you would like to know about your blood thinner treatment.

References

1. Whitlock RP, Sun JC, Fremes SE, Rubens FD, Teoh KH. Antithrombotic and Thrombolytic Therapy for Valvular Disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e576S-e600S.
2. Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Circulation. 2021;143(5):e72-e227.