Anticoagulant Medication to Prevent Strokes

If you have atrial fibrillation (afib), you also have a far greater risk of stroke. In fact, about one in five strokes in the US is related to afib, a figure that has been increasing in recent years.1

Afib overworks, weakens, and enlarges the heart, and can lead to blood pooling in the left atrium, one of the four chambers of the heart. This, in turn, can lead to the formation of blood clots that may travel from the heart to the brain. The clot blocks a blood vessel, cutting off the brain’s oxygen supply and causing a stroke.

That’s why many people with afib take anticoagulants, medications that reduce blood clotting and thus reduce your risk of stroke. You might know them as “blood thinners.”

Anticoagulants reduce the risk of clots by interrupting what is known as the “clotting cascade,” the series of chemical reactions necessary to create a blood clot. Different anticoagulants interfere at different points along that clotting cascade.

Benefits and Risks of Anticoagulant Medication

Anticoagulants reduce the risk of stroke by 64 percent, increasing your chances of living a long, productive, and healthy life.2

But there are also risks. Anticoagulants can increase your risk of bleeding because they make it harder for blood to clot. So, for instance, a fall, scrape, or even bumping into something hard could lead to uncontrolled bleeding. More severe bleeding, which can sometimes be fatal, can occur in the stomach or brain. Your doctor will balance anticoagulation benefits with bleeding risks to decide whether to start you on an anticoagulant.

Assessing Your Risk

Doctors use validated tools to assess your stroke and bleeding risk. The tool used to determine your risk of a stroke is the CHA2DS2-VASc score, while the most commonly used bleeding risk tool is the HAS-BLED score.

CHA2DS2-VASc is a simple scoring tool and is shown in the table below. You receive one point each for heart failure, high blood pressure, diabetes, vascular disease (such as a prior heart attack, peripheral artery disease, or blocked aorta), or are age 65 to 74 or female.  You receive two points each if you are age 75 or more or have had a stroke or transient ischemic attack (TIA, also called a mini-stroke). Thus, the highest possible score is nine.

Risk Factor


C Congestive heart failure/Left ventricular dysfunction


H Hypertension — high blood pressure


A2 Age≥75


D Diabetes mellitus


S2 Stroke/TIA/TE (thromboembolism)


V Vascular disease — coronary artery disease (CAD), myocardial infarction (heart attack), peripheral artery disease (PAD), or aortic plaque


A Age 65-74


Sc Sex category — Female gender


Table 1: CHA2DS2-VASc Scoring System3

The CHA2DS2-VASc is recommended in most afib guidelines for assessing stroke risk. In the current afib guidelines from both the American Heart Association, American College of Cardiology, and Heart Rhythm Society (AHA/ACC/HRS) and the European Society of Cardiology (ESC), anticoagulants should be considered for men with a CHA2DS2-VASc score of 1 and women with a score of 2 and are recommended for men with a score of 2 or greater and women with a score of 3 or greater.4,5,6 A benefit of CHA2DS2-VASc is that it assesses those who are truly low risk—0 for men and 1 for women—and thus don’t need to be on anticoagulants.6

There are two types of anticoagulant medications to prevent strokes in those with afib, Warfarin (Coumadin) and Direct Oral Anticoagulants (DOACs). Most people with afib can take either one. For those with valvular afib (defined as a mechanical heart valve or moderate-to-severe mitral stenosis), warfarin is generally recommended since DOACs have not been well studied for this.5,6

HAS-BLED is a tool used for determining bleeding risk and is recommended in the ESC afib guidelines. (No bleeding risk tools are currently recommended in the AHA/ACC/HRS afib guidelines). It is used to determine if the risk of bleeding outweighs the risk of a stroke. HAS-BLED should not be used to keep someone off of anticoagulants but instead to determine any controllable risk factors.

HAS-BLED is shown in the table below. In it, you receive one point each for high blood pressure, abnormal kidney function, abnormal liver function, prior history of stroke, prior history of bleeding, unstable INRs, age 65 or over, use of antiplatelet medications or non-steroidal anti-inflammatory drugs (NSAIDs), or excessive alcohol consumption per week. The highest possible score is nine.

A score of three or higher suggests a higher risk of bleeding. That doesn’t mean your doctor won’t start you on an anticoagulant; it means you may need to be monitored more closely or may require a different dose.

Risk Factor Score
H Hypertension — uncontrolled high blood pressure, with a systolic (top number) reading of 160 or higher 1
A Abnormal kidney or liver function (1 point each, 2 points total) 1 (each)
S Stroke — previous stroke 1
B Bleeding history or predisposition 1
L Labile INR — unstable INR (time in therapeutic range less than 60%) 1
E Elderly — age 65 or older 1
D Drugs or excessive alcohol — antiplatelet drugs (like aspirin or Plavix) or non-steroidal anti-inflammatory drugs; excessive alcoholic drinks,  greater than 14 units per week (1 point each, 2 points total) 1 (each)

Table 2: HAS-BLED Scoring System6

Numerous studies have shown that often people who should be on an anticoagulant aren’t, particularly those who are elderly.7 That may be because doctors worry about the risk of falls – a risk they may overestimate. Research shows a disconnect between the values and preferences of patients and doctors—doctors fear bleeds, but patients fear strokes. There is a fate worse than death for patients, and that is “a debilitating stroke.” Thus, patients will accept 4-5 bleeds to avoid a single stroke.8 The benefits of an anticoagulant outweigh the risks of bleeding in most people, regardless of age.9,10,11,12,13,14

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Questions to Ask Your Doctor

The bottom line is that you and your doctor need to work together to decide if anticoagulant medication is appropriate for you. Ask about your stroke and bleeding risk and understand the available options. In addition, it’s important to tell your doctor about your entire medical history, current medications (including over-the-counter medicines like aspirin), and any previous experiences taking anticoagulants.

Here are some questions to ask.

  • What is my risk of stroke?
  • Could I benefit from an anticoagulant medication?
  • Why are you suggesting this particular medication?
  • What kind of follow-up and monitoring does this medication require?
  • What are the risks or side effects of this medication?
  • Are there any dietary or lifestyle restrictions with this medication?

What to Know If You Take An Anticoagulant Medication

All anticoagulants increase the risk of bleeding, so report any signs of unusual bleeding to your healthcare professionals immediately. These include:

  • Frequent nose bleeds
  • Unusual bleeding from the gums from brushing
  • Heavier than usual menstrual bleeding or vaginal bleeding
  • Any severe bleeding
  • Red, pink, or brown urine
  • Bright red or black stools (a sign of gastrointestinal bleeding)
  • Coughing up blood or blood clots
  • Vomiting blood or vomit that looks like coffee ground
  • Headaches, feeling dizzy or weak
  • Pain, swelling, or new drainage at wound sites

It’s also essential that you let doctors and dentists know that you’re taking an anticoagulant as it may increase bleeding during any kind of surgical or dental procedure.

To learn more about the various anticoagulant medications, see Warfarin (Coumadin) or Direct Oral Anticoagulants (DOACs), or you can access one of the individual Direct Oral Anticoagulants at Apixaban (Eliquis), Dabigatran (Pradaxa), Edoxaban (Savaysa/Lixiana), or Rivaroxaban (Xarelto).

Just because you’re not in afib doesn’t mean you don’t need an anticoagulant. Learn more about this emerging thinking at Is it Afib That Causes Strokes, or Maybe Something Else?.

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