Atrial Fibrillation

Atrial fibrillation describes an irregular and often rapid heart rhythm. The irregular rhythm, or arrhythmia, results from abnormal electrical impulses in the heart. The irregularity can be continuous, or it can come and go.

Normal heart contractions begin as an electrical impulse in the right atrium. This impulse comes from an area of the atrium called the sinoatrial (SA) or sinus node, the "natural pacemaker."

• As the impulse travels through the atrium, it produces a wave of muscle contractions. This causes the atria to contract.
• The impulse reaches the atrioventricular (AV) node in the muscle wall between the 2 ventricles. There, it pauses, giving blood from the atria time to enter the ventricles.
• The impulse then continues into the ventricles, causing ventricular contraction that pushes the blood out of the heart, completing a single heartbeat.

In a person with a normal heart rate and rhythm the heart beats 50-100 times per minute.

• If the heart beats more than 100 times per minute, the heart rate is considered fast (tachycardia).
• If the heart beats less than 50 times per minute, the heart rate is considered slow (bradycardia).

In atrial fibrillation, multiple impulses travel through the atria at the same time.

• Instead of a coordinated contraction, the atrial contractions are irregular, disorganized, chaotic, and very rapid. The atria may contract at a rate of 400-600 per minute.
• These irregular impulses reach the AV node in rapid succession, but not all of them make it past the AV node. Therefore, the ventricles beat slower, often at rates of 110-180 beats per minute in an irregular rhythm.
• The resulting rapid, irregular heartbeat causes an irregular pulse and sometimes a sensation of fluttering in the chest.

Atrial fibrillation can occur in several different patterns.

• Intermittent (paroxysmal): The heart develops atrial fibrillation and typically converts back again spontaneously to normal (sinus) rhythm. The episodes may last anywhere from seconds to days.
• Persistent: Atrial fibrillation occurs in episodes, but the arrhythmia does not convert back to sinus rhythm spontaneously. Medical treatment is required to end the episode.
• Permanent: The heart is always in atrial fibrillation. Conversion back to sinus rhythm either is not possible or is deemed not appropriate for medical reasons.

Atrial fibrillation, often called A Fib, is a very common heart rhythm disorder. 

• It affects about 1% of the population, mostly people older than 50 years. This amounts to more than 2 million people.
• The risk of developing atrial fibrillation increases as we get older. About 5% of people older than 80 years have atrial fibrillation.

For many people, atrial fibrillation may cause symptoms but does no harm.

• Complications can arise, but appropriate treatment reduces these risks.
• If treated properly, atrial fibrillation rarely causes serious or life-threatening problems.

Causes

Atrial fibrillation may occur without evidence of underlying heart disease. This is more common in younger people, about half of whom have no other heart problems. This is often called lone atrial fibrillation. Some of the causes not involving the heart include the following:

• Hyperthyroidism (overactive thyroid)
• Alcohol use (holiday heart)
• Pulmonary embolism (a blood clot in the lungs)
• Pneumonia

Most commonly, atrial fibrillation occurs as a result of some other cardiac condition (secondary atrial fibrillation).

• Heart valve disease: This can be something you are born with or be caused by infection or degeneration/calcification of valves with age.
• Enlargement of the left ventricle walls (left ventricular hypertrophy)
• Coronary heart disease (or coronary artery disease): This results from atherosclerosis, deposits of fatty material inside the arteries that cause blockage or narrowing of the arteries.
• High blood pressure (hypertension)
• Cardiomyopathy (disease of the heart muscle) leading to congestive heart failure
• Sick sinus syndrome (improper production of electrical impulses because of malfunction of the SA node)
• Pericarditis (inflammation of the sac surrounding the heart)

Atrial fibrillation frequently occurs after cardiothoracic (open heart) surgery, but often resolves in a few days.

For many people with infrequent and brief episodes of atrial fibrillation, the episodes are brought on by a number of triggers. Because some of these involve excessive alcohol intake, this is sometimes called holiday heart. Some of these people are able to avoid episodes or have fewer episodes by avoiding their trigger. Common triggers include alcohol and caffeine in susceptible individuals.

Symptoms

Symptoms of atrial fibrillation vary from person to person.

• A number of people have no symptoms.
• The most common symptom in people with intermittent atrial fibrillation is palpitations, a sensation of rapid or irregular heartbeat. This may make some people very anxious. Many people also describe an irregular fluttering sensation in their chests.
• Some become light-headed or faint.
• Other symptoms include weakness, lack of energy or shortness of breath with effort, and chest pain.

When to Seek Medical Care

Call for treatment within 24 hours if you have atrial fibrillation that comes and goes, have previously been evaluated and treated, and are not experiencing chest pain, shortness of breath, weakness, or fainting.

Call if you have persistent atrial fibrillation while you are on medical therapy for the condition or you note worsening of your symptoms, or new symptoms such as fatigue or mild shortness of breath.

Call if you have questions about medications and dosages.

Call 911 for emergency medical services when atrial fibrillation occurs with any of the following:

• Severe shortness of breath
• Chest pain
• Fainting or light headedness
• Weakness
• Very rapid heartbeat or palpitations

Not all heart palpitations are atrial fibrillation, but a continuing feeling of your heart fluttering in your chest together with a fast or slow pulse should be evaluated by your doctor or at a hospital emergency department.

Exams and Tests

The evaluation may include the following tests:

Electrocardiogram(ECG): This is the primary test to determine when an arrhythmia is atrial fibrillation. The test can also sometimes reveal damage to the heart, if there is any.

Lab tests: There is no lab test that can confirm that you have atrial fibrillation. Tests are done to check for certain underlying causes of atrial fibrillation and to rule out heart damage, as from a heart attack. If you are already taking medication for atrial fibrillation, a drug level may be checked to make sure there is enough of the drug in your system to work.

• Complete blood cell count
• Markers for heart injury (enzymes such as troponins and creatine kinase [CK])
• Digoxin drug level (in patients taking this medication)
• Prothrombin time (PT) and international normalized ratio (INR): If you are taking warfarin (Coumadin) to prevent blood clotting, these tests show how well the drug is working to lower your risk of a blood clot.
• Serum electrolytes to evaluate sodium and potassium levels
• Thyroid function tests for hyperthyroidism

Chest x-ray: This imagery is used to evaluate for complications such as fluid in the lungs or to estimate heart size

Echocardiogram or transesophageal echocardiogram: This is an ultrasound test that uses sound waves to make a picture of the inside of the heart while it is beating.

• This test is done to identify problems in heart valves or ventricular function or to look for blood clots in the atria.
• This very safe test uses the same technique used to check a fetus in pregnancy.

Ambulatory electrocardiogram (ECG): This test involves wearing a monitor for a period of time (usually 24-48 hours) to try to document the arrhythmia while you go about your everyday activities.

• The device you wear for 24 to 48 hours is called a Holter monitor.
• An Event monitor is a device that can be worn for 1-2 weeks and records the heart rhythm when it is activated by the patient.
• These tests may be used if your symptoms come and go and your ECGs do not reveal the arrhythmia.

Treatment

In making the diagnosis, your health care provider will consider the severity of symptoms and whether they are new or have been going on for some time. You may be referred to a specialist in heart disorders (cardiologist) during this evaluation. Choice of treatment for atrial fibrillation depends on the type you have, the severity of your symptoms, the underlying cause, and your overall health.

Self-Care at Home

There is no effective home treatment for atrial fibrillation. If your doctor recommends lifestyle changes or prescribes medicine, follow his or her recommendations exactly. This is the only way to see whether the treatment works.

Medications

The choice of medication depends on the type of atrial fibrillation you have, the underlying cause, your other medical conditions and overall health, and the other medications you take. Ironically, many anti-arrhythmia medications may induce abnormal heart rhythms.

Anti-arrhythmia medications

• Miscellaneous anti-arrhythmia medications: These drugs control the heart rhythm rather than rate. They reduce the frequency and duration of atrial fibrillation episodes. They are often given to prevent return of atrial fibrillation after cardioversion. The most commonly used drugs are amiodarone (Cordarone, Pacerone), sotalol (Betapace), propafenone (Rythmol), and flecainide (Tambocor). Overall, these drugs are 50-70% effective.
• Beta-blockers: These drugs slow the heart rate by decreasing the rate of the SA node and by slowing conduction through the AV node. Therefore, the heart's demand for oxygen is decreased, and the blood pressure is stabilized. Examples include propranolol (Inderal) or metoprolol (Lopressor Toprol XL).
• Calcium channel blockers: These drugs also slow heart rate by similar mechanisms as beta-blockers. Verapamil (Calan, Isoptin) and diltiazem (Cardizem) are examples of calcium channel blockers.
• Digoxin (Lanoxin): This drug decreases the conductivity of electrical impulses through the AV node, but onset of action is slower than beta-blockers and calcium-blockers. Digoxin is currently used primarily in patients with associated heart disease, such as a poorly functioning left ventricle.
• Dofetilide (Tikosyn): This is an oral anti-arrhythmic drug that must be initiated in the hospital over a three-day period. Hospitalization is needed to closely monitor the heart rhythm during the initial dosing period. If the atrial fibrillation responds favorably during the initial dosing, a maintenance dose is established to be continued at home.

Other drugs

• Warfarin (Coumadin): This drug is an anticoagulant (blood thinner). It reduces the ability of the blood to clot. It lowers the risk of an unwanted blood clot forming in the heart or in a blood vessel. Atrial fibrillation increases the risk of forming such blood clots. There are other anticoagulant drugs, but warfarin is the only one taken in pill form and is usually given for daily use. It is extremely important to follow the exact dosing prescribed and to have regular blood tests (INR) when recommended by your doctor.

Surgery

Before the development of catheter ablation, open heart surgery was done to interrupt conducting pathways in both atria. This is called the surgical maze procedure. Maze surgery is usually considered in patients who need some other type of heart surgery, such as valve repair or coronary artery bypass surgery.

Follow-up

If you have no heart disease and medications succeed in controlling your heart rate, you can be sent home from the emergency room. You should follow-up with your health care provider within 48 hours.

If your rhythm does not convert to normal by itself, you may need electrical cardioversion, or defibrillation.

• If you have been in atrial fibrillation longer than 48 hours, you will need three weeks of treatment with an anticoagulant medication, such as warfarin, before electric shock and for four weeks after.
• Anyone with underlying heart disease or those that do not respond to rate controlling treatment may require hospital care

Prevention

If you do not have atrial fibrillation, you can lower your chance of getting this arrhythmia by reducing your risk factors. This includes risk factors for coronary heart disease and high blood pressure.

• Do not smoke.
• Maintain a healthy weight.
• Make nutritious, low-fat foods the basis of what you eat.
• Take part in moderately strenuous physical activity for at least 30 minutes every day.
• Control high blood pressure and high cholesterol.
• Use alcohol in moderation, if at all.
• Use caffeine in moderation, if at all. Avoid other stimulants.

If you have atrial fibrillation, your health care provider may prescribe treatments for the underlying cause and to prevent future episodes of atrial fibrillation. These treatments might include any of the following (see Medical treatment for more information).

• Medications
• Cardio version
• Pacemaker
• Radiofrequency ablation
• Maze surgery

The most dangerous complication of atrial fibrillation is stroke.

• Someone with atrial fibrillation is about 3-5 times more likely to have a stroke than someone who does not have atrial fibrillation.
• The risk of stroke from atrial fibrillation for people aged 50-59 years is about 1.5%. For those aged 80-89 years, the risk is about 30%.
• Warfarin (Coumadin), when taken in appropriate doses, and monitored carefully, reduces this risk of stroke by over two thirds.
• It is important to know that clinical trial data has shown that you can live just as long with atrial fibrillation with a controlled heart rate, for example, with medications, plus Coumadin as in normal sinus rhythm (AFFIRM trial).

Another complication of atrial fibrillation is heart failure.

• In heart failure, the heart no longer contracts and pumps as strongly as it should.
• The very rapid contraction of the ventricles in atrial fibrillation can gradually weaken the muscle walls of the ventricles.
• This is uncommon, however, because most people seek treatment for atrial fibrillation before the heart begins to fail.

For most people with atrial fibrillation, relatively simple treatment dramatically lowers the risk of serious outcome. People with infrequent and brief episodes of atrial fibrillation may need no further treatment than learning to avoid the triggers of their episodes, such as caffeine, alcohol, or overeating.