THE BASICS: “What is it?”

Did you know that your heart pumps five to six quarts of blood every minute? That’s the equivalent of 2,000 gallons of blood powering through your body every day to deliver the oxygen and nutrients that keep you alive.

How does your heart accomplish this amazing feat? By beating (contracting and expanding) 100,000 times every day. So it makes sense that any problems with the way your heart beats can cause problems with your health.

Atrial fibrillation is a heartbeat problem: a rapid, irregular, and even chaotic heart rate that results when your heart rhythm (the electrical activity in your heart) becomes rapid and irregular in the atria, the two top chambers of your heart.

  • The term “atrial” refers to these two top chambers, the left atrium and the right atrium.
  • The two bottom chambers of your heart are the left and right ventricles.

Your heart beats (pumps blood) in response to a series of electrical signals:

  • Each beat starts with a signal produced in the sinus node, located in the right atrium (right upper chamber of your heart).
  • The sinus node is often called “the heart’s natural pacemaker.”
  • A normal heart rhythm is called normal sinus rhythm (NSR).
  • As the signal from the sinus node passes through the right and then the left atria, these chambers contract and pump blood down into the ventricles.
  • Next, the signal travels through the atrioventricular (AV) node, which connects the two upper chambers (atria) with the two lower ones—the right and left ventricles.
  • Exiting the AV node, the signal enters the ventricles, which contract and pump blood out of the heart.
  • The right ventricle pumps blood to the lungs.
  • The left ventricle pumps blood into the rest of the body.

In atrial fibrillation, the electrical signals don’t start in the sinus node and don’t travel normally. As a result, the beating of the two upper chambers of your heart (the atria) is “out of synch” with the beating of the two lower chambers (the ventricles).

  • The atria beat so rapidly they “quiver” (fibrillate), overloading the AV node with electrical signals attempting to reach the ventricles.

The three most common types of atrial fibrillation are:

  • Paroxysmal (also called occasional) atrial fibrillation – In this condition, symptoms come and go. They may be mild or severe, and a symptom “episode” can last from just seconds to days.
  • Persistent (also called chronic) atrial fibrillation – Symptoms are continuous. They stop only when the atrial fibrillation is treated.
  • Longstanding persistent atrial fibrillation (formerly called permanent atrial fibrillation) – Atrial fibrillation symptoms continue despite treatment.

Paroxysmal and persistent atrial fibrillation can develop into the longstanding persistent form.

A condition known as lone atrial fibrillation is not due to structural heart problems, and its cause is often unknown. Fortunately, lone atrial fibrillation rarely leads to serious complications.

About 2.7 million Americans have atrial fibrillation, which is:

  • The most common heart rhythm disorder
  • The most common serious heart-rhythm problem in people over age 65

Most people with atrial fibrillation have it for life and need lifelong treatment to:

  • Keep symptoms under control
  • Prevent serious complications, particularly stroke

Symptoms of atrial fibrillation include:

  • Palpitations—the uncomfortable feeling that your heart is racing and irregular. Instead of a normal 60 to 100 beats per minute, your heart rate may be 100 to 175 beats per minute.
  • Shortness of breath
  • Weakness
  • Lightheadedness
  • Confusion
  • Low blood pressure
  • Chest pain . Seek medical help immediately if you have chest pain, which could mean you’re having a heart attack.

Having atrial fibrillation symptoms does not mean you’re having a heart attack: Atrial fibrillation and heart attack are two different things with different causes.

Up to 30 percent of people with atrial fibrillation do not have symptoms.

  • However, they still need treatment to prevent blood clotting and stroke.

Causes of atrial fibrillation include:

  • High blood pressure
  • Abnormal heart valves
  • Heart attack
  • One or more heart defects that were present at birth (congenital)
  • Previous heart surgery
  • Sick sinus syndrome—problems with the heart’s “natural pacemaker”
  • An overactive thyroid gland or other metabolic imbalance
  • Emphysema or other lung disease such as pneumonia
  • Viral infection
  • Stress due to pneumonia, other illnesses, or surgery
  • Drinking alcoholic beverages, particularly binge drinking (having five drinks in two hours for men, or four drinks for women): This can trigger episodes of atrial fibrillation.
  • Stimulants (which may increase heart rate and raise blood pressure) such as caffeine, tobacco, or certain medications, including:
  • Over-the-counter (OTC) cough and cold products containing pseudoephedrine
  • Diet pills
  • Recreational drugs

A number of factors can increase your risk of atrial fibrillation, including:

  • Age: Your risk increases as you get older.
  • Heart disease: Heart attack, heart surgery, heart valve disorders—these and other heart problems increase your risk.
  • High blood pressure: Poorly controlled high blood pressure can also raise your risk.
  • Family history: If others in your family have or had it, you’re at higher risk for developing it.
  • Other chronic medical problems: These include thyroid problems and sleep apnea.
  • Habitually drinking more than a moderate amount of alcoholic beverages daily (two drinks for men, one for women). Studies show that this drinking pattern strongly increases your risk of developing atrial fibrillation.

In about 10 percent of people with atrial fibrillation, there is no association with another disease or disorder.

The same risk factors exist for a condition called atrial flutter, in which:

  • Atrial rhythm is abnormal, but less so than in atrial fibrillation.

Atrial flutter and atrial fibrillation also have similar symptoms and causes. In addition:

  • Atrial flutter can develop into atrial fibrillation.

Although atrial fibrillation isn’t typically life-threatening, it is serious, because it can lead to, or be associated with, two serious complications:

Stroke: The disorganized heart rhythm of atrial fibrillation may cause blood pooling and clotting in the atria (upper chambers of the heart). A blood clot that detaches from the heart and travels to the brain may block blood flow and cause a stroke (loss of function, such as speech, movement, and/or memory, in stroke-damaged areas of the brain).

It’s estimated that 15 to 20 percent of people who have strokes also have atrial fibrillation.

Risk factors for stroke in people with atrial fibrillation include:

  • Advancing age
  • High blood pressure
  • Diabetes
  • A history of a previous stroke or heart failure

Blood thinner medications are prescribed for people with atrial fibrillation to lower the risk of stroke and clot-related damage to other organs.

Heart failure: Untreated or uncontrolled, atrial fibrillation can weaken the heart to the point where it can’t pump the amount of blood your body needs to function normally.

Now that you’ve learned more about atrial fibrillation, you’re ready to seek the care you may need if you have it. Next step:

  • Getting to know the health professionals who can help


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