The Link Between Atrial Fibrillation and Stroke

What Is Atrial Fibrillation?

Atrial fibrillation or “A fib” is the most common type of arrhythmia. It is often described as an “irregularly irregular” heartbeat. This abnormal rhythm occurs when the two top chambers of the heart (the atria) receive erratic signals resulting in an irregularly irregular beat. This rhythm can occur for short periods of time or can last indefinitely if left untreated.

A fib often has no symptoms. However, when they occur, the most common symptoms include:

• Light-headedness
• Fluttering in your chest
• Fatigue
• Shortness of breath
• Feeling of a rapid heartrate

If you experience any of these symptoms, speak with your healthcare provider to determine if you may have A fib.

Learn more about 5 Most Common Arrhythmias

How Atrial Fibrillation Increases Your Risk of Stroke

In AF, the atria do not contract effectively, which can lead to the formation of blood clots. If a blood clot forms in the atria, it can travel to the brain and block blood flow to a part of the brain, causing a stroke.

Here's how atrial fibrillation can lead to a stroke:

1. When the atria do not contract properly, blood can pool and stagnate. Stagnant blood is more likely to form blood clots.
2. If a blood clot forms in the atria, it can dislodge and travel through the bloodstream. This is called an embolism.
3. If the blood clot reaches the brain and lodges in a small blood vessel, it can block blood flow to a specific area of the brain. This blockage deprives the brain tissue of oxygen and nutrients, leading to a stroke.

This results in the characteristic signs of an ischemic stroke such as lack of coordination, and numbness in part of the body. Without rapid intervention, this lack of blood flow can even lead to permanent brain damage.

Strokes that occur as a result of A fib are often thought be more severe and result in worse outcomes than strokes from other causes. This is why it is essential to minimize this risk when possible.

What is Stroke?

What is the CHADS2 Score?

There are many other factors which increase your risk of stroke, in addition to experiencing A fib. The CHADS2 score is a system that clinicians use in order to determine your risk of experiencing a stroke if you currently have A fib. This works as an aid to determine if you are at high enough risk to warrant preventative prescription medications to decrease this risk

It does this by assigning points if you fit any of the following criteria:

• Chronic heart failure: 1 point
• High blood pressure: 1 point
• Age 75 years or older: 1 point
• Diabetes: 1 point
• Previous stroke/transient ischemic attack (TIA)*: 2 points

* A TIA is often referred to as a “mini stroke”. It is also caused by a blockage in a blood vessel of the brain and while the symptoms are similar initially, a TIA typically resolves completely within 24 hours.

The scores are added up to give a total CHADS2 score ranging from 0 to 6. The higher the CHADS2 score, the greater the risk of stroke in patients with AF.

Here's how the scores are interpreted:

• 0: Low risk (annual stroke rate approximately 1.9%)
• 1: Moderate risk (annual stroke rate approximately 2.8%)
• 2 or higher: High risk (annual stroke rate approximately 4% to 12.5%)

Based on the CHADS2 score, healthcare providers can make informed decisions about the need for anticoagulant therapy, such as prescribing medications like warfarin or direct oral anticoagulants (DOACs) to reduce the risk of stroke in patients with AF.

CHA2DS2 VASc Score

There is also a newer scoring system called the CHA2DS2 VASc score which is more detailed and slightly more accurate. It builds upon the CHADS2 score by incorporating additional risk factors to provide a more comprehensive evaluation of stroke risk.

The components of the CHA2DS2-VASc score include:

• Chronic heart failure: 1 point
• High blood pressure: 1 point
• Age 75 years or older: 2 points
• Diabetes: 1 point
• Previous stroke/transient ischemic attack (TIA): 2 points
• High blood pressure: 1 point
• Vascular disease (e.g., prior heart attack, peripheral artery disease): 1 point
• Age 65 to 74 years: 1 point
• Sex category (female gender): 1 point

Similar to the CHADS2 score, each factor is assigned a score, and the scores are then added up to determine the total CHA2DS2-VASc score, which ranges from 0 to 9. The higher the score, the greater the risk of stroke in patients with AF

Here's how the scores are interpreted:

• 0: Very low risk (annual stroke rate less than 1%)
• 1: Low risk (annual stroke rate approximately 1.3%)
• 2 or higher: Moderate to high risk (annual stroke rate approximately 2.2% to 18.2%)

CHA2DS2-VASc score provides a more refined assessment of stroke risk compared to the CHADS2 score, particularly for patients with a CHADS2 score of 0 or 1. By considering additional factors like vascular disease, age 65 to 74 years, and female gender, the CHA2DS2-VASc score helps identify individuals who may still benefit from anticoagulation therapy despite having a lower CHADS2 score.

Treatment Options to Manage Your Risk

The treatment for atrial fibrillation (AF) and stroke risk management typically involves a combination of strategies aimed at controlling the heart rhythm, preventing blood clot formation, and reducing the risk of stroke.

Rate control

The goal is to control the heart rate in individuals with AF to improve symptoms and prevent excessive strain on the heart. Medications such as beta-blockers, calcium channel blockers, or digoxin may be prescribed to achieve this.

Rhythm control

The objective is to restore and maintain normal sinus rhythm (regular heart rhythm). This can be achieved through medications called antiarrhythmic drugs, electrical cardioversion (a controlled electric shock to reset the heart rhythm), or catheter-based procedures like ablation to eliminate abnormal electrical pathways in the heart.

Anticoagulation therapy

Since AF increases the risk of blood clot formation and subsequent stroke, anticoagulant medications are often prescribed to prevent clot formation. The choice of anticoagulant depends on various factors and may include vitamin K antagonists (e.g., warfarin) or direct oral anticoagulants (DOACs) like apixaban, dabigatran, edoxaban, or rivaroxaban. The selection of anticoagulant is based on factors such as patient age, kidney function, bleeding risk, and other individual considerations.

In general, DOACs are preferred for most individuals, other than those with mechanical valve replacements or mitral stenosis. Both of these medications work by decreasing the tendency for blood to clot. This decreasing clotting risk therefore decreases your risk of stroke.

The greatest risk of taking anticoagulant medications is your increased risk of bleeding. As these medications push your blood system away from clotting, they can sometimes work “too well” and cause unwanted bleeds. It's important to weigh the pros and cons of starting an anticoagulant medication, in order to ensure that your risk of stroke outweighs the risk of developing a bleed.

Blood thinners don't really thin blood

It is also essential to stay on top of your other medical conditions, including A fib, to decrease your risk of stroke. Even if you have conditions that increase the risk of stroke, managing them well as well as maintaining a healthy diet with plenty of exercise is also likely to help decrease your risk.