Blood Thinners for Atrial Fibrillation: How and Why They’re Used

The effects of AFib can promote the formation of blood clots that can travel to other areas of the body and block off blood vessels. When this happens, the affected area cannot get enough oxygen-rich blood and damage can occur.

One of the major complications of AFib is ischemic stroke, which happens when a blood vessel in the brain is blocked. It’s estimated that people with AFib have a fivefold increased risk of stroke.

Blood thinners are a drug that helps to prevent blood clots from forming. You may also see them called anticoagulants.

To help reduce the risk of stroke and other clot-related complications from AFib, your doctor may prescribe a blood thinner. These medications can help to reduce the risk of stroke by more than 50% and also prevent stroke recurrence.

Not everyone with AFib needs to take blood thinners. After AFib is diagnosed, your doctor will estimate your risk of stroke.

To do this, they’ll likely use a CHA₂DS₂-VASc score. This calculates your stroke risk per year using various factors, including:

• age
• sex
• history of previous a blood clot, transient ischemic attack (TIA), or stroke
• other health conditions, including:
  • high blood pressure
  • heart failure
  • previous heart attack
  • diabetes
  • vascular disease

If your CHA2DS2-Vasc score indicates an elevated risk of stroke, your doctor may recommend a blood thinner to lower your risk.

There are several types of blood thinners used for AFib. One is warfarin (Coumadin), a blood thinner called a vitamin K antagonist. Warfarin is taken orally.

Your daily dose of warfarin is based on your body’s response to a particular dose. An international normalized ratio (INR) blood test determines your appropriate dose and to adjust dosing as needed.

Your INR is measured frequently when you begin taking warfarin, and can be measured less frequently once a stable dose is determined.

Direct-acting oral anticoagulants (DOACs) are another blood thinner used for AFib. Most guidelines give preference to these drugs over warfarin. There are several DOACs available:

• apixaban (Eliquis)
• dabigatran (Pradaxa)
• edoxaban (Savaysa)
• rivaroxaban (Xarelto)

DOACs are also taken orally. Depending on the DOAC prescribed, you’ll take it once or twice daily.

Unlike warfarin, DOACs have fixed doses and do not require lab monitoring. In some cases, these medications are better than warfarin at reducing stroke and have less bleeding complications.

The main complication of using blood thinners for AFib is the risk of bleeding. This is because blood thinners affect your blood’s ability to clot.

Most of the time, this bleeding is minor. For example, if you cut your finger, it may take your blood longer to clot.

However, bleeding can also be more severe and potentially life threatening. This can include bleeding in your digestive system or inside of your skull.

Before prescribing blood thinners for your AFib, your doctor will estimate your risk of bleeding. This is often done using a HAS-BLED score, which considers the following factors:

• predisposition to bleeding or a history of bleeding events
• history of stroke
• underlying health issues, including
  • high blood pressure
  • liver disease
  • kidney disease
• use of medications that may predispose to bleeding
• alcohol use
• unstable INR
• age

People with a higher HAS-BLED score will need additional caution and regular monitoring if they begin taking blood thinners for their AFib.

Many people with AFib take blood thinners to reduce their risk of stroke or other complications due to blood clots. These drugs work by reducing the blood’s ability to clot.

Not everyone with AFib needs blood thinners.

Your doctor will estimate your stroke risk before recommending blood thinners. Because blood thinners can cause potentially serious bleeding, doctors will also assess your bleeding risk.