Understanding Atrial Fibrillation

The Normal Heart

Your heart is a muscle that works like a pump. The main job of your heart is to pump blood throughout your body. There are four chambers; two upper chambers called atria and two lower chambers called ventricles.

The atria collect blood returning to the heart and transfer it to the ventricles. The ventricles squeeze the blood out to the rest of your body.

The different chambers in your heart work together. The right atria and ventricle pump blood to your lungs to pick up oxygen. The left atria and ventricle pump the oxygen-rich blood to the rest of your body.

The pumping of your heart is regulated by an electrical current or impulse—much like a spark plug in a car. The electrical impulse starts in the sinoatrial (SA) node and then spreads throughout both atria like ripples in a pond. This causes both atria to contract, squeezing blood into the ventricles.

Medical illustration of a heart section highlighting atriums, nodes, ventricles and bundle branches.

The impulse then travels down to the atrioventricular (AV) node which is like a wire that connects it to the ventricles. The AV node splits into two branches, the left bundle branch and the right bundle branch. From the AV node, the impulse spreads through the bundle branches allowing the even spread of the electrical signal to both ventricles at the same time. 

Both ventricles then contract to squeeze the blood out to your body.

When the heart is working properly, this cycle repeats 50 to 150 times per minute.

Atrial Fibrillation

In atrial fibrillation, the electrical impulses start firing from all over both atria in an irregular pattern. With too many random triggers firing, your heart beats irregularly and, sometimes, too fast. 

Medical illustration showing the atria, nodes and ventricles of the heart, through which electrical impulses fire irregularly or too quickly in atrial fibrillation.

In atrial fibrillation, the electrical impulses are generated outside of the SA node. This causes the heart to beat irregularly, interrupting the smooth flow of blood through the atria. 

There are different types of atrial fibrillation:

  • Paroxysmal: You have bouts of atrial fibrillation that come and go. They may last from a few seconds up to a few days, but usually, they start and stop on their own.
  • Persistent: Your episodes of atrial fibrillation last longer than a week and usually will not stop without some kind of treatment.
  • Permanent : Your heart is always in atrial fibrillation. Your doctor may have tried several different types of treatments, but nothing has been able to keep your heart in a normal rhythm. It is unlikely that your heart will ever go back to a normal rhythm.

In many cases, patients who have atrial fibrillation lead perfectly normal lives.

Causes of Atrial Fibrillation

Atrial fibrillation is a common condition in older adults. According to the Heart and Stroke Foundation, approximately 1 in 10 people over the age of 80 has atrial fibrillation.

Different types of heart conditions such as heart valve disease, heart attacks or heart failure can cause atrial fibrillation. Any type of infection that causes inflammation of the heart muscle or the outer layer of the heart may lead to atrial fibrillation. Some people who are born with heart problems may develop atrial fibrillation later in life.

Other health conditions such as high blood pressure, diabetes, sleep apnea, or lung disease may also increase the risk of developing atrial fibrillation.

In many cases, people develop atrial fibrillation for reasons that cannot be figured out.

Atrial Flutter

  • Atrial flutter is similar to atrial fibrillation but less common.
  • Many patients have both atrial flutter and fibrillation.
  • The two are very closely related; in fact, the treatments for both are similar and the risk of stroke from both is the same.

Atrial Flutter Is Different 

In atrial flutter, the electrical impulses are more regular but still rapid and inefficient. Some people with atrial flutter feel quite fine and don’t have any symptoms.

Other people may have symptoms similar to atrial fibrillation. 

Common Symptoms of Atrial Fibrillation

Atrial fibrillation can cause any of the following symptoms:

  • A rapid heartbeat or a feeling “skipped” heart beats
  • Breathing problems (shortness of breath)
  • Dizziness or feeling faint
  • Tiredness or lack of energy
  • Chest pain, tightness or pressure
  • Anxiety, feeling like something is not quite right

These are the most common symptoms. You may feel only one or two, or you may have different symptoms.

Many people have no symptoms at all.

In fact, many people with atrial fibrillation are able to keep their symptoms at a minimum and have an excellent quality of life. 

Diagnosing Atrial Fibrillation

Often, atrial fibrillation is diagnosed when people develop symptoms and go to their doctor or to the emergency department. Other times, it is identified during routine examinations.

In order to diagnose atrial fibrillation, your doctor will review your medical history, conduct a full physical exam and order some tests. 

Some of the more common tests that your doctor may order include:

  • Electrocardiogram (ECG): This test records the electrical activity of your heart and is important for confirming whether your heart rhythm is in atrial fibrillation
  • Holter monitor: This test is like an ECG, except that it records your heart’s electrical activity for up to 48 hours. It requires you to be connected to a small portable device that you carry with you in a pouch or on a shoulder strap for two days. The Holter monitor is helpful if you have only occasional bouts of atrial fibrillation that did not show up on an ECG.
  • Event recorder: Similar to a Holter Monitor, you wear this device for up to two weeks. You press the “record” button whenever you experience anything you think is abnormal, such as rapid heartbeats, dizziness or chest pain. These recorders may also pick up episodes automatically.
  • Echocardiogram: This is a special ultrasound test for the heart that lets your doctor have a closer look at the chambers and valves in your heart.