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Atrial Fibrillation

  • A heart rhythm problem that causes irregular beating (arrhythmia) and abnormal blood flow
  • Symptoms include fatigue, shortness of breath, and rapid or erratic heart beat
  • Treatment includes catheter ablation, cardioversion, medication
  • Involves Cardiovascular Medicine, Electrophysiology & Cardiac Arrhythmia Program


If you've ever had your heart skip a beat, you might know what atrial fibrillation feels like. Atrial fibrillation is a heart rhythm disturbance also known as arrhythmia. It causes the rapid beating—almost quivering—of the heart’s two upper chambers, the right and left atria. 

However, this quivering isn't forceful enough to efficiently move blood out of the upper chambers of the heart to the lower chambers of the heart. Almost 2.7 million Americans live with atrial fibrillation. 

Abnormal blood flow has two negative consequences. First of all, stagnation of blood in the left atrium can cause a blood clot. When a clot moves from the heart to the brain, a patient can have a stroke. Patients with atrial fibrillation can also feel unwell, tired, short of breath, and unfocused.

What are the different types of atrial fibrillation?

There are two different types of atrial fibrillation:

  • Paroxysmal atrial fibrillation: It refers to atrial fibrillation that comes and goes. For example, some patients might experience the erratic heartbeat for periods of minutes, hours or days over the course of several months.
  • Persistent atrial fibrillation: This is when the characteristic electric problems in the heart do not go away. People with this type are constantly in arrhythmia unless it’s reversed with cardioversion, an electrical shock to the heart.

What are the symptoms of atrial fibrillation?

A fairly high percentage of patients in atrial fibrillation will feel tired and short of breath and feel their hearts beating rapidly and erratically. Others report that they have developed anxiety or say that they “can’t think straight.”

That’s because atrial fibrillation causes the heart’s natural pacemaker, the sinoatrial node, to cede control to the atrioventricular (AV) node, an electrical connection that sits between the upper and the lower chambers.

“That’s not supposed to control the heart rate, but now it does,” says Mark Marieb, MD, associate professor of Cardiology at Yale Medicine. ”In most cases, too many of the rapid electrical waves travel from the atria to the pumps (ventricles) and the heart beats rapidly. The irregularity of the signals that travel through the AV node make the lower chambers—the heart’s ventricles—beat erratically.

Though symptoms typically don’t worsen over time, they also don’t go away, Dr. Marieb says. But for patients with paroxysmal atrial fibrillation, the frequency of episodes often increase over time.

Some patients never exhibit symptoms despite having atrial fibrillation; they remain at an increased risk of stroke, however.

“Those patients could present with just a stroke,” he says. “Before that, they don’t know they have it.”

How is atrial fibrillation diagnosed?

People with symptoms visit their cardiologists, where they undergo a full physical exam, share their medical history and have an electrocardiogram (EKG) to chart the heart’s beat and other electrical activity. If a patient has persistent atrial fibrillation, the EKG will catch it.

On the other hand, if a patient has paroxysmal atrial fibrillation, the heart may beat completely normally during the visit. In that case, doctors ask patients to wear a device called a Holter monitor for one or two days, in an attempt to catch an irregularity.

However, even this monitor can miss an irregular heart flutter if it is episodic, says Dr. Marieb. 

In those cases, there are devices that patients can wear for 30 days and even implantable chips that can monitor heartbeat for up to three years.

“The diagnosis is important, but the main challenge is treatment,” Dr. Marieb says.

What are the risk factors of atrial fibrillation?

Age is a big risk factor. While only 2 percent of people under 65 years old have atrial fibrillation, the incidence can reach up to 9 percent for those above 65, according to the Centers for Disease Control and Prevention.

Like other commonly known heart diseases, such as blocked arteries, atrial fibrillation’s risk factors also include being overweight, having high blood pressure, drinking alcohol, having sleep apnea and having a family history of the disease.

At the moment, incidence of atrial fibrillation is rising dramatically.

“Even if you control for all those things, it seems to be increasing,” says Dr. Marieb. “And we don’t really know why.”

How can atrial fibrillation be treated?

There is no miracle surgery or miracle pill for atrial fibrillation. "It’s a complicated disease," says Dr. Marieb. “There’s a lot of tailoring going on to figure out what’s best for each patient." The goal of treatment is to go after the many causes of atrial fibrillation.

“We cannot at the moment change a person’s genetics or age, but we can attempt to aggressively treat obesity, inactivity, hypertension (high blood pressure) and sleep apnea and reduce alcohol intake,” he says. “Obviously, the patient has to play a major role in modifying these factors.”

The main objective, which is to prevent stroke, can be pursued in the following ways:

Ablation: To directly treat the atrial fibrillation, doctors can also perform a procedure called catheter ablation. In this procedure, doctors use wires, inserted through a veins in the leg, to either freeze or burn out the tissue in the atria that is responsible for the arrhythmia. This is best thought of as an electrical solution—the idea is to target spots where the waves and circuits have gotten off-kilter. 

Though this process is usually successful, it isn’t nearly 100 percent effective, says Dr. Marieb, The degree of success depends upon the type of atrial fibrillation (paroxysmal versus persistent), the size of the atria, and how long a patient has had the arrhythmia, among other factors. The process may have to be repeated.

Unfortunately, there can also be serious risks to this invasive procedure, says Dr. Marieb.

“Improving the success rate and reducing the risks of ablation procedures is a priority for researchers, and is one of the major areas of investigation in our field,” he says.

Cardioversion: The other approach, known as rhythm control, is to try to keep the patient’s heart in a normal rhythm. That can be done through cardioversion, which is a shock that temporarily brings the heart’s rhythm back to normal. 

Though this has a 95 percent chance of converting the heart back to its regular beating, the downside of this approach is that it does nothing to prevent the heart from going back into atrial fibrillation. It usually lasts no longer than a year, and many times atrial fibrillation can recur immediately or within days to weeks.

Medication: Doctors almost always prescribe blood thinners to atrial fibrillation patients. These anticoagulant drugs prevent blood clots. If clots are unable to form, then a patient’s risk of stroke goes down dramatically. There is always a risk of bleeding from these medications, but if it occurs, it is usually not life threatening. In addition, numerous studies have shown that the risk of a stroke is much higher than bleeding.

Not all patients are treated with blood thinners: For a patient who has short episodes, and has a low risk of stroke due to a young age, lack of heart failure, diabetes, or high blood pressure, the bleeding risk of blood thinners could end up being worse than the problem.

One next step is to put a patient on a medication that slows the heart down in addition to prescribing blood thinners. That’s called the rate control and anticoagulation strategy.

Rhythm medications attempt to keep the rhythm normal. But as Dr. Marieb says, “They work sometimes, but not nearly 100 percent.” 

Another approach to treatment is to block off the site where the vast majority of clots form, which is a pouch called the left atrial appendage. This does not directly treat the atrial fibrillation, but is thought to reduce the risk of stroke. If a clot can’t form, then the risk of stroke will drop. Doctors are working to obstruct the appendage in several different ways: by tying off the entrance, using a sort of lasso or by inserting a plug from inside the heart, walling off the entrance.

There are some surgical ways of remedying atrial fibrillation that aim to accomplish the same goal as ablation, but that go through or under ribs and work on the heart from the outside. This is more invasive approach. There are also a combination of procedures known as “hybrid” or “convergent” procedures, in which catheter ablation and surgical ablation are combined.

Even with treatments that address the underlying causes, patients tend to stay on their blood thinners to prevent stroke, in case the arrhythmia returns.

What makes Yale Medicine’s approach to atrial fibrillation unique?

There are several reasons why Yale Medicine excels at atrial fibrillation treatment. "We have very experienced operators in terms of doing the ablation,” says Dr. Marieb. “We have rotor mapping technology that we use.”

This is a state-of-the-art tool that helps doctors to identify the sources of the arrhythmia—one of the most difficult parts of treating atrial fibrillation—while reducing fluoroscopy and X-ray exposure.

At Yale Medicine, cardiac specialists work closely with general cardiologists to diagnose and treat the patient. These doctors also conduct cutting-edge research and clinical trials related to arrhythmia.