Anticlotting Medications and Congenital Heart Disease

Quick Facts

  • Many people with congenital heart disease need medication to help prevent blood clots.
  • Anticoagulants and antiplatelet agents help lower the risk of problems caused by blood clots.

person putting pills in their hand

Many people with congenital heart disease need medication to help prevent blood clots. These medications include anticoagulants or antiplatelet agents.

Your healthcare team may prescribe these medications if you have a heart valve replacement, certain heart rhythm problems or specific congenital heart conditions, such as after a Fontan operation.

These medications help lower the risk of problems caused by blood clots, such as clots forming on artificial valves or clots traveling to the brain and causing a stroke. Most are taken by mouth. In some cases, they’re given through an IV or injection.

Because these medications affect blood clotting, bleeding is a possible side effect. Tell your healthcare professional if you bruise easily or notice unusual bleeding, such as bleeding gums or nosebleeds.

Talk with your dentist and healthcare team before dental work or surgery. You may need to change your medications or delay non-urgent procedures to lower the risk of bleeding.

Anticoagulants

Anticoagulants are often used for people with certain heart rhythm problems, such as atrial fibrillation, blood clots in the veins or after heart valve replacement.

Warfarin

Warfarin is an anticoagulant taken by mouth. It helps prevent blood clots from forming and keeps existing blood clots from getting bigger.

Warfarin increases the risk of bleeding. If you take warfarin, you’ll need regular blood tests to check how fast your blood clots. This test is called the INR (international normalized ratio). Your healthcare team will adjust your dose to keep your INR at a safe level for your heart condition. It’s important to take warfarin exactly as prescribed.

Many medications can interact with warfarin and change your INR. These can include:

  • Some antibiotics
  • Some pain medicines, such as NSAIDs (for example, ibuprofen or naproxen), which can increase bleeding risk
  • Certain acid-reflux medications

In general, avoid aspirin when taking warfarin unless your healthcare professional tells you it’s safe. Always check with your healthcare team before starting any new medication.

Some foods, vitamins and herbal supplements can also affect how warfarin works. Talk with your cardiologist about your diet and before taking any supplements.

If you are pregnant or planning to become pregnant, talk with your healthcare team right away. Warfarin can harm a developing baby, especially in the first trimester. If you are pregnant or planning pregnancy, your care team may switch to heparin during pregnancy or at certain times. Warfarin can cause harm to a developing baby.

Read more about warfarin.

Heparin

Heparin is given through an IV or by injection.

IV heparin works quickly to prevent blood clots. When it’s stopped, its effect wears off quickly.

Heparin and low-molecular-weight heparin can also be given by injection instead of IV. This may be used when anticoagulant treatment is needed for a longer time, such as during pregnancy. It eliminates the need for an IV line long-term. Blood tests may be needed to make sure the dose is correct, depending on the type of heparin used.

Some anticoagulants taken by mouth stay in the body longer. Before planned surgery or dental work, these medications may need to be stopped and heparin used instead for a short time. This is called bridging, meaning one medication is temporarily replaced with another to reduce the risk of clotting and bleeding around the time of a procedure. Your doctor will decide if this is needed based on your condition.

Antiplatelet agents

Antiplatelet agents may be used in some people after certain heart procedures (such as atrial septal defect repair) or for specific heart conditions, depending on individual risk. Aspirin and clopidogrel are common antiplatelet medicines taken by mouth. They help prevent blood clots by stopping platelets from sticking together.

Aspirin can upset your stomach and increase the risk of bleeding. It may need to be stopped before surgery or dental work.

Clopidogrel doesn’t require regular blood tests, but it can increase bleeding risk for several days. Your healthcare team will tell you if and when to stop taking it before surgery or dental procedures.

Last Reviewed: Jun 10, 2026

* Some medications are called blood thinners because they can help stop a blood clot from forming. There are two main types of blood thinners that people commonly take: anticoagulants such as warfarin, dabigatran and rivaroxaban, and antiplatelet drugs such as aspirin or clopidogrel. Each type of medication has a specific role to prevent a blood clot from forming or causing a blocked blood vessel, heart attack or stroke. 
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