What is atrial fibrillation?

Atrial fibrillation (also called AF or A Fib) is the most common form of abnormal heart rhythm. It is a very fast, uncontrolled heart rhythm caused when the upper chambers of the heart (the atria) quiver instead of beating. During AF, the upper chambers of the heart can beat between 350 and 600 times per minute. Atrial fibrillation can produce quite unpleasant palpitations and sometimes breathlessness. Until just a few years ago AF was thought to be a "nuisance" arrhythmia with few consequences. However, more recent investigation has shown that because the pumping function of the upper chambers isn’t working properly, the blood is not completely emptied from the heart’s chambers, causing it to pool and sometimes clot. AF can therefore increase the risk of stroke or heart failure.

Research has yet to uncover the definitive cause of AF and this type of arrhythmia can occur at any age, but its prevalence tends to increase with age and affects men slightly more often than women.

Several different terms are used to describe AF. Lone atrial fibrillation is a form of AF with no identifiable cause or associated abnormalities of the heart. Paroxysmal AF is characterized by brief episodes of the arrhythmia, which can resolve by themselves. Paroxysmal AF occurs intermittently and varies in frequency and duration from a few seconds to more protracted episodes lasting several hours or even days. Both lone and paroxysmal AF tend to be seen more often in younger people aged 30-50 years. In persistent AF, the episodes require some form of intervention to return the heart rhythm back to normal. For those with permanent AF, intervention (if successful at all) only restores normal heart rhythm for a brief time.

Neurogenic AF indicates an imbalance in the nervous system regulation of the heart. One type of neurogenic atrial fibrillation, vagal AF, occurs in conjunction with enhanced parasympathetic response from the vagus nerve. Stimulation of the vagus nerve causes the heart rate to slow down and the rerest period of the atria to shorten. Typically, vagal AF occurs more frequently at rest or following a meal, and is usually in seen men who are between 30 and 50 years of age. Often patients note the onset of this type of AF is preceded by a period of progressive bradycardia (slow heart rate) and in this case, medications such as beta blockers may actually worsen the AF.

Adrenergic AF is another type of neurogenic atrial fibrillation that occurs as a result of excessive adrenaline that comes from stimulation of the sympathetic portion ("fight or flight"response) of the nervous system. Sympathetic effects on the heart include increased rate and force of contraction. This type of AF is most likely to occur during the day and may be associated with emotional stress or physical exertion. Unlike the case of vagal AF, medical therapy with beta blockers may be quite helpful in controlling this form of atrial fibrillation.

Atrial flutter is a more organized but still fast arrhythmia that causes the upper chambers to beat between 240 and 300 beats per minute. Atrial flutter can be triggered when an impulse circles the heart’s upper chambers instead of moving to the lower chambers. In atrial flutter, usually only every other flutter wave reaches the heart’s lower chambers.

Another common atrial rhythm is sinus tachycardia. Sinus tachycardia is a rate of more than 100 beats per minute. It results when the SA node sends electrical impulses faster than usual. As the rate in the upper chambers increases, so does the rate in the lower chambers of the heart, thus speeding the heart to meet an increased need in the body (e.g., fever, exercise). This is a normal response and, as such, sinus tachycardia is considered a normal rhythm.

Supraventricular (originating above the ventricles) tachycardia (SVT) is a series of fast atrial contractions that can cause the atrium to beat up to 240 times per minute. Though it is rarely serious, SVT can be frightening for the patient who may feel this fast rhythm.

How AF affects quality of life.
Some people have absolutely no awareness of being in atrial fibrillation, while others know precisely the moment when their heart rhythm changes from normal sinus rhythm to AF. Many patients describe the irregular, often rapid beats of the heart in AF as an uncomfortable sensation inside of the chest with a sudden and keen awareness of every heartbeat. This may be accompanied by shortness of breath, sweating, chest pain, dizziness, fainting, exercise intolerance and extreme fatigue.

Others describe feelings of heightened anxiety, especially when AF is first discovered. For some patients, the pattern of atrial fibrillation may progress from a paroxysmal and infrequent event to become a chronic condition. Often, there is a worsening or progression of the symptoms to the point where  many patients feel incapable of carrying out normal daily activities.

It is difficult for those who have not experienced AF to understand the impact that it can have on daily life. Battling the physical and emotional effects of AF is debilitating, yet no one knows that the battle exists because there are few outward physical symptoms. Employers, family members and even treating physicians may be unaware of the decrease in functional capacity that AF causes. As a result, patients with AF often feel that others think that they are "exaggerating" their symptoms.

Because AF is so unpredictable, patients are often reluctant to travel and may even avoid committing to social engagements. Frequent trips to the hospital for repeated episodes of atrial fibrillation can completely disrupt life, causing significant emotional and physical distress to both AF sufferers and their families.

The content of these pages is not intended to be a substitute for professional medical advice. Always seek the advice of your doctor or other qualified healthcare provider with any questions you may have regarding a medical condition or medical treatment.