Blood Thinners for Afib: Who Needs Them and Why

If you have atrial fibrillation (Afib) you may wonder whether blood thinners are right for you.

After all, Afib is an irregular heart rhythm. Why would blood thinners need to be part of your management strategy?

Good question! And while there are other treatments for Afib, blood thinners are often an important part of the approach to keeping you healthy.

We talked with cardiologist Mandeep Bhargava, MD, about Afib and blood thinners and why they may be the key to lowering your risk of stroke.

AFib and your stroke risk

Atrial fibrillation is a rapid and irregular rhythm of the upper chambers (atria) of the heart.

When you have Afib, the upper chambers of your heart are activated at a very fast rate — more than 250 to 350 beats per minute (bpm). For comparison, the expected resting heart rate for an adult is about 60 to 100 bpm.

When you have Afib due to such rapid rates, your atria can’t squeeze as well as they should. That allows blood to pool and swirl in the left upper chamber, which puts you at increased risk for blood clots to form.

Those clots can then move to your brain and other critical organs (a process called embolization) and put that organ in danger. Your brain is the most commonly affected organ in this process. That’s why people with Afib are at increased risk of stroke.

Why blood thinners for Afib? 

Blood thinners (also called anticoagulants) reduce your risk of a stroke by making it less likely that clots will form. 

“Blood clots can lead to stroke and also heart attacks and pulmonary embolism,” Dr. Bhargava reports. “Taking anticoagulants when indicated can help your body break down blood clots if they form — or prevent them from forming in the first place. In patients with atrial fibrillation, taking anticoagulants can lower your risk of stroke.”

Anticoagulant medications act by inhibiting the various clotting factors in your blood. That makes them useful in dissolving or preventing clots in relatively low-pressure chambers, like the left atrium (upper left chamber), which is where blood clots related to afib are most likely to form.

Common blood thinners for people with Afib include medications like:

• Heparin and fondaparinux. These are injectable medications that may be used in hospital settings for people with Afib. They work by activating a protein in your blood called antithrombin III or Factor Xa, which kicks your body’s anti-clotting processes into gear.
• Warfarin. This is a vitamin K antagonist. It works by inactivating the various clotting factors that need vitamin K for their activation. Warfarin is an oral medication that many people with Afib take daily. But its dose must be regulated and monitored with frequent blood tests — at least every three or four weeks.
• Direct oral anticoagulants (DOACs). These include common medications like rivaroxaban (Xarelto®), Apixaban (Eliquis®) Edoxaban (Savaysa®) and betrixaban (Bevyxxa®). DOACs usually have a fixed dose (one size fits all) based on your age, weight and kidney function. They don’t require regular blood tests to monitor their dose. They also have many fewer drug and food interactions, all of which have made them much more popular than warfarin in recent years.

How to determine your stroke score

If you have Afib, it doesn’t necessarily mean that blood thinners are always needed for you.

It’s a matter of weighing the risk of stroke being off anticoagulants versus the risk of bleeding on anticoagulants.

Healthcare providers use a measurement scale known as a CHA₂DS₂Vasc score to help determine your risk for a stroke.

Here’s how to find your CHA₂DS₂Vasc score:

• 1 point if you have congestive heart failure
• 1 point if you have hypertension
• 1 point if you’re between the ages of 65 and 74 
• 2 points if you’re age 75 or more
• 1 point if you have diabetes
• 2 points if you have a history of stroke or transient ischemic attack (TIA)
• 1 point if you have any form of vascular disease, including coronary artery disease
• 1 point if you are female and if you already have at least one other point (the score for a female in the absence of any other risk factor is 0)

Add up your score.

If you have Afib and you’re male and your CHA₂DS₂Vasc score is 2 or more, most guidelines recommend blood thinners. The same applies if you’re female and your CHA₂DS₂Vasc score is 3 or more.

Anticoagulation is also recommended if you have hypertrophic cardiomyopathy, hyperthyroidism and rheumatic heart disease-related atrial fibrillation despite the CHA₂DS₂Vasc score.

The CHA₂DS₂Vasc score is for people who don't have a history of excessive bleeding or a predisposition toward bleeding. People with a higher risk of bleeding can be assessed using the HAS-BLED score to help determine whether blood thinners are right for them.

• H — Hypertension
• A — Abnormal liver or renal function
• S — Stroke
• B — Bleeding history or predisposition
• L — Labile INR (blood clotting levels that are unstable or frequently changing)
• E — Elderly(typically age 65 or older)
• D — Drug or alcohol use

“People who are more susceptible to bleeding may not be good candidates for blood thinners,” Dr. Bhargava clarifies. “If your blood is already less prone to forming clots and you take blood thinners, you’re at risk for excessive bleeding from even a minor injury.”

Talk with a healthcare provider to understand the risks and benefits of taking a blood thinner and whether it’s the right option to help manage your Afib.