Why Atrial Fibrillation Matters

What are the consequences of atrial fibrillation?

Atrial fibrillation, also called AFib or AF, can feel weird and frightening. But an “attack of AFib” usually doesn’t have harmful consequences by itself. The real danger is the increased risk for stroke. Even when symptoms are not noticeable, AFib can increase your risk for stroke and related heart problems.

What causes AFib?

Sometimes the cause of AFib is unknown. Other times, it is the result of damage to the heart's electrical system from other conditions, including:

• Longstanding, uncontrolled high blood pressure
• Coronary artery disease
• Complications after surgery. It's the most common complication after heart surgery.

View an animation of AFib.

Usually, the most serious risk from AFib is that it can lead to other medical problems, including:

• Stroke
• Heart failure
• Chronic fatigue
• Additional heart rhythm problems
• Inconsistent blood supply

Learn about the important connection between atrial fibrillation, high blood pressure and stroke.

How does AFib lead to stroke?

• The heartbeat seems to quiver (or fibrillate) in an erratic way. The upper chambers (the atria) of the heart contract irregularly.
• The contraction fails. Imagine wringing out a sponge. Without a good squeeze, water will still be left in the sponge. In the same way, when a heart contraction is either too fast or too uneven, it doesn’t completely squeeze the blood from the atria into the next chamber.
• Blood pools in the atria. Blood not completely pumped out of the atria can remain and may pool there.
• Risks of clotting increase. When blood has the opportunity to pool, it also has the opportunity to clot.
• Clots can travel and cause blockages. If a blood clot forms in the atria, it can be pumped out of the heart to the brain. This blocks the blood supply to an artery in the brain and causes a stroke. This type of stroke is called an embolic stroke or some doctors call it a cardioembolic stroke.

How does AFib lead to heart failure?

Heart failure means that the heart isn’t pumping enough blood to meet the body's needs. AFib can lead to heart failure because the heart is beating so fast that it never properly fills up with blood to pump out to the body.

As a result, when the heart doesn't efficiently pump the blood forward with strong contractions, symptoms develop because:

• Blood can “back up" in the pulmonary veins, the vessels that return oxygen-rich blood from the lungs to the heart. This can cause fluid to back up into the lungs.
• When AFib causes heart failure, fluid in the lungs can cause fatigue and shortness of breath. Oxygen-rich blood is not being delivered to the body and brain, causing physical and mental fatigue and reduced stamina. Fluid also can build up in the feet, ankles and legs, causing heart failure-related weight gain.

How does AFib lead to additional heart rhythm problems?

Basic answer: The heart’s electrical system stops working properly and fails to keep the heart chambers in rhythm.

Thorough answer: Every heartbeat is controlled by the heart’s electrical system. To understand why AFib is a problem, it's helpful to understand the normal patterns of the heart’s electrical system.

View an animation of a normal heartbeat.

In the heart’s normal electrical pattern:

• The current travels from top to bottom. The heartbeat starts at the top of the heart and – like an electrical wave – current travels to the lower parts of the heart, signaling the tissue to contract.
• The sinoatrial (SA) node starts the contraction in the top of the heart. The right atrium (one of the two types of chambers of the heart) houses a group of cells called the sinoatrial node. In healthy adults, the node fires off between 60 to 100 heartbeats per minute. The electrical wave moves through the atria to “gatekeeper node.”
• The atrioventricular (AV) node regulates the timing for the lower portion of the heart. This node serves as a gatekeeper for all the electrical pulses going through the atria (top sections) to the ventricles (bottom sections). The electrical pulses are delayed at the AV node before they are allowed to move into the ventricles. This delay gives the ventricles extra time to finish filling with blood before contracting.
• The ventricles contract and pump blood out to the lungs and the body.

Electrical problems in AFib:

• In AFib, the SA node may not start the contraction. Instead, the contraction might start randomly in other areas of the atria or even in the pulmonary veins.
• In AFib, the electrical current doesn’t flow in an organized top-to-bottom fashion. Instead, contractions are rapid and disorganized.
• In AFib, the AV node often can’t regulate the chaotic current. It does its best to protect the ventricle from extra electrical impulses, but it can’t stop all of them. As a consequence, the ventricle beats more often than it should – giving rise to noticeable breathlessness and fatigue.
• When the beat is off, the blood supply can be unpredictable. Even though the ventricles may be beating faster than normal, they aren't beating as fast as the atria. Thus, the atria and ventricles no longer beat in a coordinated way. This creates a fast and irregular heart rhythm. In AFib, the ventricles may beat 80 to 175 times a minute, in contrast to the normal rate of 60 to 100 beats a minute.

The amount of blood pumped out of the ventricles to the body is based on the randomness of the atrial beats.

The body may get rapid, small amounts of blood and occasional larger amounts of blood. The amount will depend on how much blood has flowed from the atria to the ventricles with each beat.

Can AFib simply go away?

Yes. While spontaneous remission is rare, it does happen. It simply goes away. However, it is still something that you and your health care professional will want to monitor, because some people live with AFib and do not feel the symptoms. The risks are still present.

Overall, most risks, symptoms and consequences of AFib are related to how fast the heart is beating and how often rhythm disturbances occur.

AFib may be brief, with symptoms that come and go. An AFib episode may resolve on its own or it may be persistent and require treatment. Sometimes AFib is permanent, and medicines or other treatments can't restore a normal heart rhythm.

It’s important to work with your health care professional to determine your treatment needs and understand your treatment options. It's also important to maintain a heart-healthy lifestyle to reduce your overall risks as much as possible.