Atrial fibrillation (AFib) increases the risk for stroke. So stroke prevention is an important part of treatment for atrial fibrillation.
AFib is a type of abnormal heart rhythm. The heart has 4 chambers: 2 upper atria and 2 lower ventricles. There is also an electrical system in the heart that sends signals to control the heartbeat. As signals move through the heart, it tells the heart's upper chambers (atria) and lower chambers (ventricles) when to squeeze and pump the blood out (contract) and relax. This moves blood through the heart and out to the body and lungs.
AFib causes the atria to quiver or “fibrillate” instead of pump in an orderly fashion. The disorganized or chaotic electrical signal spreads to the ventricles, and it causes the ventricles to contract irregularly. The contraction (pumping) of the atria and the ventricles is no longer coordinated. So the amount of blood pumped out to the body will vary with each heartbeat. The ventricles may not be able to pump enough blood to the body to keep things running efficiently.
Because blood also doesn't flow as well from the atria to the ventricles, it can pool. This pooling can cause blood clots to form inside the heart. In the left atria, there is a pouch in the muscle wall. This pouch is called the left atrial appendage (LAA). It can often be large and have multiple lobes, which can permit blood pooling and clot formation. It is in this appendage that most of the blood clots form when someone is in atrial fibrillation. The clots can then get pumped out of the heart and go to the brain to cause a stroke. For this reason, providers advise that many people who have AFib take a blood thinner to prevent clot formation and reduce their risk of stroke.
Taking medicine to thin the blood helps prevent stroke, but it also increases your risk of bleeding. You may have signs of excess bleeding if your blood isn’t clotting enough. You may have these symptoms:
Bleeding from the gums
Blood in the urine or stool
An unusually severe headache might also be a sign of bleeding in the brain.
Healthcare providers use a risk-based scoring system to decide if you need blood-thinner medicine (anticoagulant) to help prevent clots from forming and causing a stroke. The scoring system takes into account other risk factors for stroke and assigns each a point value. These risk factors include:
History of heart failure
History of high blood pressure
Age 65 to 74 years old
Age 75 or older
Past stroke or transient ischemic attack
History of vascular disease
Assigned female at birth
Your healthcare provider may advise using a blood-thinner medicine depending on your risk factors for stroke.
Your healthcare provider may also look at your risk for falls and bleeding when deciding whether to advise a blood thinner. They may use a tool to help identify your risk for bleeding. Your healthcare provider can use this information to help suggest the best way to treat your AFib.
Your healthcare provider will work closely with you to find the right medicines for you to help prevent stroke. They will consider both your health history and your preferences.
Some of the medicines that your provider may prescribe include:
Antiplatelet medicines, such as aspirin or clopidogrel
Anticoagulation (blood-thinning) medicines, such as warfarin, or medicines called direct-acting oral anticoagulants (DOACs), such as dabigatran, rivaroxaban, apixaban, or edoxaban.
These types of medicines help to prevent blood clots in different ways:
Antiplatelet medicines affect platelets, which are fragments of cells involved in clotting
Anticoagulation medicines work on other parts of the complex blood-clotting pathway in the body
Each person's risk for stroke is evaluated on an individual basis. If you have risk factors for stroke, you will likely need blood-thinning medicines.
Your healthcare provider may advise DOAC medicines unless you have moderate to severe narrowing of the heart valve (mitral stenosis) or a mechanical heart valve. With DOACs, no regular blood tests are needed to monitor how your blood is clotting. But you may need blood tests of your kidney and liver function before starting these medicines and then every so often while you are taking them.
Warfarin is the medicine often recommended for treatment of AFib in people who have moderate to severe mitral valve disease or a mechanical heart valve. With warfarin, you need blood tests on a regular basis to make sure the blood is clotting the right amount. Your healthcare provider can measure clotting with a prothrombin time test. This is sometimes called a PT or pro time test. The results are reported as the international normalized ratio (INR). The INR is a standard way of reporting the PT by all laboratories. If your INR is too high, the dose of warfarin may be lowered because you are at higher risk for bleeding. If your INR is too low, your risk for blood clots is higher. So your healthcare provider may increase your dose of warfarin. Warfarin also interacts with certain foods. For example, foods high in vitamin K, such as leafy green vegetables, can make warfarin less effective. This could raise your risk for blood clots. That's why it is important to eat a consistent amount of foods high in vitamin K.
Talk with your healthcare provider about the medicine prescribed to learn all you can about it. Also, be sure all your healthcare providers know that you take blood-thinning medicines.
A device may be used to close off the left atrial appendage in some circumstances, to prevent stroke without having to use lifelong blood thinners. The left atrial appendage is the area within the heart where most blood clots form. By closing this area off, any clots that form there cannot get out to travel to the brain to cause a stroke. The device is implanted without heart surgery. This device is not appropriate for everyone. It is generally considered in those who are at high risk for stroke, as well as high risk for bleeding. Even with the device, you may need to take blood thinners in the short-term.
There are risks of using medicines that help prevent blood clotting and stroke. These medicines also increase the risk of bleeding. This bleeding can occur anywhere in the body. It can be dangerous if it happens in the digestive tract. Bleeding inside the brain is also very dangerous. This can actually cause a stroke, something the medicine was supposed to help prevent.
Warfarin interacts with many other medications and can be affected by your diet. This can lead to either a blood clot and stroke if you aren't getting enough warfarin or increase your risk of bleeding if you are getting too much. For this reason, warfarin needs to be closely monitored. Often, dose adjustments need to be made on a regular basis.
Your healthcare team will work hard to make sure you are getting the right amount of medicine for you by balancing these risks. They will only prescribe medicines if the benefits of stroke prevention are greater than the risks for bleeding.
Your healthcare provider may give you additional instructions about managing your atrial fibrillation. Make sure all your healthcare providers, dentists, and pharmacists know if you are taking medicines to prevent clots. Talk with your healthcare provider before taking any new medicines, vitamins, or supplements, even if they are over the counter. Any of these can affect the way blood thinning medicines work. Also talk with your provider about your diet if you take warfarin. Certain foods like leafy green vegetables can change your INR. You don’t have to give these up, but you need to keep the amount that you eat about the same from day to day. Take your medicine exactly as your provider tells you. Wear a medic alert bracelet. Be sure to keep a card with you at all times that says you are taking a blood thinner. Make sure someone in your family knows your medicines.
Your healthcare provider may give you other instructions about how to lower your risk for stroke. These might include:
Reducing cholesterol through lifestyle changes or medicines
Being physically active
Staying at a healthy weight to lower your risk for AFib returning
Limiting how much alcohol you drink
Eating a heart-healthy diet
See a healthcare provider right away if you have any of the following signs:
Unusual or severe headache
Confusion, weakness, or numbness
Bleeding that will not stop
Coughing or vomiting blood
Bright red, bloody stools or black, tarry stools
Fall or injury to the head
Plan to see your provider soon if your symptoms are slowly getting worse. Also see them if you have any new mild symptoms or side effects.