Tampa Bay Adult Congenital Heart Disease Clinic presents

Heart Health through Education

Atrial Fibrillation

Written by Marie Cheine

Edited by Hector Fontanet, M.D., FACC

April, 2009

 Characterization:

Atrial fibrillation (a quivering of the upper chambers of the heart) occurs when rapid, uncoordinated, electrical signals in the heart’s two upper chambers cause them to contract rapidly and irregularly, preventing  the heart’s upper and lower chambers to work together as they should. Atrial fibrillation is the most common form of irregular heart rhythm. Over two million Americans have it. It is present in 6% of our population over the age of 65 and 10% in the population over the age of 80. Atrial fibrillation can be continuous, can come and go (paroxysmal atrial fibrillation) or it can be permanent.

Common Causes:

Abnormalities or damage to the heart's structure, are the most common causes of atrial fibrillation. These include coronary artery disease, (hardening of the arteries) previous heart attack, congenital heart defects, sick sinus syndrome, abnormal heart valves, and congestive heart failure (weak heart muscle), as is long-term high blood pressure, disorders of the lung (sleep apnea, COPD and emphysema) and overactive thyroid. Some people who have atrial fibrillation don't have underlying structural heart disease at all. This is a condition called lone atrial fibrillation. In lone atrial fibrillation, the cause is often unclear but possible causes include an exposure to certain medications, caffeine, and tobacco or alcohol, and viral infections. Stress due to surgery, pneumonia or other illness is also a possible cause of atrial fibrillation.

Symptoms & Complications:

Signs and symptoms of atrial fibrillation vary from person to person. In fact, this abnormal rhythm may cause no symptoms at all. Some patients can live with the condition for years before symptoms become uncomfortable or atrial fibrillation is diagnosed on routine exam. However, many have an awareness of rapid heart beats or sudden flutter in the heart, shortness of breath, palpitations, dizziness, fatigue or even chest pain. These symptoms can be bothersome to patients without any structural heart disease, but pose minimal or no medical risk. Serious complications are usually rare in lone atrial fibrillation.

However, for patients with coronary artery disease, Diabetes Mellitus or high blood pressure, atrial fibrillation can be dangerous. It can lead to tachycardia-induced cardiomyopathy, heart failure and stroke (the most serious clinical consequence of atrial fibrillation).

Diagnosis, Screening & Follow Up:

Proper diagnosis of atrial fibrillation by detailed medical history and physical examination as well as EKG and/or holter monitoring is necessary. Your heart specialist is best suited to establish the etiology of the rhythm disturbance.

If atrial fibrillation is confirmed, echocardiogram to assess heart and valve structures and laboratory analysis for assessment of liver, renal, thyroid function, cell count, electrolytes and coagulation will be performed to determine if there is an underlying cardiac or other medical condition that is causing atrial fibrillation.  In most cases patients will be treated with a blood thinner (Coumadin or warfarin) to reduce the risk of stroke. If the patient is under age 40, has normal heart function and low clinical probability for coronary artery disease, no further diagnostic testing will be performed. A follow up appointment to assess anticoagulation and initiation of antiarrhythmic therapy will be scheduled prior to patient leaving the office.

In some cases, emergency treatment for atrial fibrillation is necessary to convert the heart back to a normal rhythm by the use of IV medications or electric cardioversion.

©       The strategy is aimed at establishing cause or etiology, controlling the heart rate and associated symptoms and protection against strokes with anticoagulation therapy.

Extended Evaluation:

Patients under age 40 with abnormal heart function or patients older than 40 years or in whom coronary artery disease is suspected on the basis of risk factors will be scheduled for myocardial perfusion SPECT imaging.  Older patients (over age 60) with suspected sick sinus syndrome/bradyarrhythmias will be scheduled for Holter Monitoring.

Second Evaluation:

Second consultation is obtained to discuss results and implications of diagnostic testing, treatment options, initiation of antiarrhythmic therapy and assessment of anticoagulation.

Long-term treatment options vary depending upon the underlying cause of the abnormal heart rhythm. Treatment includes restoring and maintaining normal heart rhythm or controlling heart rate.

Third Evaluation:

Third consultation is obtained to assessment of toxicity of antiarrhythmic therapy, anticoagulation efficacy (PT/INR), EKG. Certain medications require periodic monitoring of liver and thyroid function through blood testing every 3-4 months.

Patients will then be referred back to their primary care provider and scheduled for cardiology follow up every 3 months.

Fourth and future Evaluation:

Follow up post-cardioversion or routine scheduled follow up.

 

Treatment Options:

Your heart specialist will discuss treatment strategies with you. In nearly all patients prevention of stroke with anticoagulation will be necessary. However, controlling the heart rate or restoring heart rhythm to normal is a choice that requires careful consideration of the risks and benefits to each individual patient.

The goals of treatment for atrial fibrillation are prevention of stroke, control of heart rate, resolution of symptoms and restoration of normal rhythm if possible. The prevention of stroke in nearly all patients with atrial fibrillation is carried out by the anticoagulation (blood thinning) with Coumadin® or Warfarin. It has been shown in clinical trials that treatment with aspirin or Plavix® is not sufficient to prevent stroke in this class of patients. Common medications for rate control include calcium channel blockers, beta-blockers and digoxin. Although this group of medications is effective in controlling the heart rate they are not usually effective in restoring normal heart rhythm. Medications that convert and maintain normal rhythm are called antiarrhythmics. Long term options for treatment are dependent upon the underlying cause (etiology) of each individual case.

Based on the results recently learned from various clinical trials, most asymptomatic patients will be best managed with rate control and anticoagulation only, avoiding potential side effects of antiarrhythmics. However, some patients remain symptomatic after rate is controlled. For these patients, or patients who have underlying heart disease, the use of antiarrhythmics has advantages, most importantly the improvement of quality of life, improving heart function in patients with heart failure and potentially allowing the discontinuation of anticoagulation therapy.

Antiarrhythmics, nevertheless, are a complex class of medications and carry risk and potential side effects. The most effective medication in this class is Amiodarone, which works by slowing nerve impulses in the heart and acting directly on the heart cells to synchronize the electrical impulses. These medications should be used judiciously and patients must be closely monitored while using them. In some cases, these medications can cause life threatening rhythm disturbances in patients with certain heart conditions. For this reason, your doctor may elect to start this type of medication in the hospital under careful observation.

In cases where symptoms or side effects remain intolerable or a patient fails medical therapy, other therapies such as electrical cardioversion (electric shock to restore normal rhythm) or radiofrequency ablation can be considered. Radiofrequency ablation (RFA) is an invasive procedure performed in the hospital in the cardiac catheterization laboratory. During this procedure, x-rays and sophisticated computer electric mapping techniques are utilized to position a special catheter at the exact place in the heart where the abnormal rhythm is generated and “microwave-like” energy is transmitted to destroy this area and prevent the abnormal rhythm. Radiofrequency ablation is only performed by electrophysiologists who have special training in this procedure. Your physician can refer you to an electrophysiologist with this expertise if necessary.

Summary:

In summary, atrial fibrillation is a common non life threatening rhythm disturbance of the heart. The approach for treatment varies with each patient. Whether it is rate control or restoration of normal rhythm, with any one of many modalities, the risks and benefits of medical and/or invasive treatment must be weighed carefully and discussed in detail with your physician.

Sources:

American Heart Association

Atrial Fibrillation Foundation
Cleveland Clinic Journal of Medicine
Electrophysiology Division University of California San Francisco

(http://cardiology.ucsf.edu/ep/afibnyou/index.html)

Heart Rhythm Society
Medline Plus

New England Journal of Medicine
American Heart Association