Blood Thinners for Heart Failure

Topic Overview

If the function of your heart is very poor, you may be at risk for developing a blood clot, called a thrombus, inside your heart. Blood clots in the heart are a risk factor for the type of stroke that is caused by a small piece of the clot breaking off and traveling to the brain. In certain circumstances, you may need to take a blood thinner (such as warfarin) to prevent a blood clot from forming in your heart. If you have heart failure, most doctors would agree that you should take warfarin if you:

  • Have atrial fibrillation, an irregular heart rhythm which significantly increases the risk of forming a blood clot in your heart that can travel to the brain and cause a stroke.
  • Have an aneurysm of your heart. This refers to a portion of the heart wall that bulges out and does not contract when the rest of the heart contracts.
  • Have had a previous stroke caused by a blood clot from your heart.
  • Have an existing blood clot in your heart.

Many doctors also prescribe warfarin when the percentage of blood pumped out of the heart with each beat (ejection fraction) is very low, because the lower the ejection fraction, the higher your risk of forming a blood clot and having a stroke. However, doctors do not agree on how low the ejection fraction needs to be to warrant warfarin therapy, and some doctors do not prescribe warfarin based on the ejection fraction alone.

The major risk of taking warfarin is that it also can cause bleeding. You are at risk for severe bleeding from warfarin if, for example, you have an active stomach ulcer.


Author Robin Parks, MS
Editor Kathleen M. Ariss, MS
Editor Marianne Flagg
Associate Editor Terrina Vail
Associate Editor Pat Truman, MATC
Primary Medical Reviewer Caroline S. Rhoads, MD - Internal Medicine
Specialist Medical Reviewer Robert A. Kloner, MD, PhD - Cardiology
Last Updated August 25, 2008

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