Blood Thinners After Heart Valve Surgery

If you have heart valve replacement surgery, you will be prescribed a blood thinner (a.k.a. an anticoagulant) upon discharge from the hospital. Long-term blood thinner medication guidelines differ depending on what kind of valve is used, be it artificial (mechanical/man-made) or biological (from human or animal tissue). You may need to take this drug for the rest of your life.

A doctor explaining a model to patient in examination room
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Both valve types require specific medication regimens, and research has changed over the years to reflect the benefits and risks of blood thinners in particular.

When and Why Blood Thinners Are Recommended

Healthcare providers prescribe blood thinners after a mechanical valve replacement for two reasons. First, man-made valves are constructed of carbon and titanium, and your blood may have a tendency to “stick” to the artificial valve. That can cause the valve to clog and malfunction.

While the artificial valve itself is not sticky, blood may cling to it in a way that does not occur with a natural heart valve. If a clot forms, it could also break off and travel to the heart or brain, causing a heart attack or stroke.

Secondly, an artificial valve can create “turbulence” in the blood flowing through your heart, meaning that the blood doesn’t flow quite as smoothly as it does with a natural valve. This creates another opportunity for blood clots to form.

A bioprosthetic or "tissue" valve created from cow or pig tissue usually doesn't require a blood thinner long-term, but research has shown benefits of taking a blood thinner for several months after surgery to help prevent possible clotting.

Researchers have been working to change the materials and design of mechanical valves to make them less prone to clotting. Valves may eventually be made of carbon-based materials (no metal).

Meanwhile, a 2019 study by engineers at the University of Bern in Switzerland identified a design flaw in mechanical valves that allows for turbulence to develop and suggested a design change that could eliminate this and make blood thinners less necessary. More research is needed, however, and any real change could take years.

Common Blood Thinners After Valve Replacement

The first-line blood thinner prescribed to valve patients is Coumadin (warfarin). Warfarin is generally effective, with patients having a 1% to 4% incidence rate per year of thromboembolic events (a clot breaks loose and clogs another blood vessel) and a 2% to 9% annual rate of "significant" bleeding events.

Aspirin may also be recommended by itself or in combination with warfarin.

Given the bleeding risks of warfarin and the need for dose monitoring, other anticoagulants are being studied as possible alternatives for valve replacement patients, but research is in its infancy and they are not widely used for this purpose:

  • Xa inhibitors like apixaban: In a small, short-term study of pigs implanted with mechanical valves, apixaban showed lower bleeding risk compared to warfarin.
  • Xarelto (rivaroxaban): A blood thinner used to treat atrial fibrillation, rivaroxaban has begun to be researched for use in valve replacements. A small, short-term study of seven patients over three months showed no negative outcomes from rivaroxaban therapy.

Short-term blood thinner use for a bioprosthetic valve patient is not as intensive as a mechanical valve patient's regimen. The need for thinners rarely lasts more than 90 days. Some patients may only require aspirin or warfarin, while others receive a combination of the two.

Bleeding risk is a factor here. One U.S. Veterans Administration study of more than 9,000 bioprosthetic patients, conducted between 2005 and 2015, found that aspirin alone was effective in 46% of participants. While the aspirin/warfarin combination patients (18% of participants) showed no increased risk of mortality or blood vessel obstruction, they had a higher bleeding risk than the aspirin-only patients.

Life on Blood Thinners

Depending on the anticoagulant chosen, your healthcare provider will monitor your results in the months after your surgery to ensure you are taking the right dose. The dosage may be adjusted based on the results of your clotting time to make sure your blood is not too “thin” or not “thin” enough.

Please be aware that you should tell your healthcare providers, whether it is a medical practitioner or a dentist, that you’ve had a valve surgery and you are taking a blood thinner. You should inform your dentist when you schedule your appointment, as you may need to take prophylactic antibiotics before your visit. This is also true before surgery in general.

This will also be important information to share before minor procedures, such as a colonoscopy, and before any changes are made in your medications.

Activities and Diet

You will bleed more easily and clot more slowly while on these drugs, and you may also bruise more easily as well. This will require you to be more cautious in your daily activities to prevent injury, particularly if you are physically active.

Warfarin patients should also limit their alcohol consumption, as alcohol can affect how your body processes the drug. Vitamin K can also inhibit warfarin's effectiveness, so talk to your healthcare provider about consuming K-rich foods like leafy green vegetables (lettuce, spinach, kale, as well as broccoli).

Major changes in your diet, such as starting a new weight loss regimen on New Year's Day, can cause changes in how thin your blood is and should be discussed with your healthcare provider—particularly if the amount of vegetables you will be eating will be dramatically changed and you are on warfarin.

When to Call Your Healthcare Provider

According to the American Heart Association, "unusual" bleeding while on warfarin includes bleeding from the gums, blood in urine or stool, dark stool, nosebleed, or vomiting blood.

If you take warfarin, contact your healthcare provider immediately if you experience any unusual bleeding, bleeding that won't stop, or if you experience a fall or injury.

A Word From Verywell

Taking a blood thinner requires some changes to your daily life and a need to commit to frequent monitoring. While it may, at times, feel like a hassle, the effort is worth it, as it can help you avoid a heart attack or stroke. Work with your healthcare provider to find the ideal drug or combination of drugs to lower your clot risk and maintain your quality of life.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  7. Durães AR, Bitar YSL, Lima MLG, et al. Usefulness and Safety of Rivaroxaban in Patients Following Isolated Mitral Valve Replacement With a Mechanical Prosthesis. Am J Cardiol. 2018;122(6):1047-1050. doi:10.1016/j.amjcard.2018.06.015

  8. Bravata DM, Coffing JM, Kansagara D, et al. Association Between Antithrombotic Medication Use After Bioprosthetic Aortic Valve Replacement and Outcomes in the Veterans Health Administration SystemJAMA Surg. 2019;154(2):e184679. doi:10.1001/jamasurg.2018.4679

  9. Blood Thinners and Dental Care. The American Academy of Oral Medicine.

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Additional Reading

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.