Dr. Wilber Su, FACC, is a cardiologist and cardiac electrophysiologist.
Question: My cardiologist says I have atrial fibrillation. What is A Fib and is it common?
Answer: You're not alone. Atrial Fibrillation (commonly referred to as A Fib or AF) is one of the most common heart rhythm abnormalities, and is perhaps the most confusing for the patient to understand.
Your heart is the body's main circulation pump. The heart pump is a mechanical pump with chambers and valves. How the heart pumps is regulated by electricity that flows through the heart. Therefore, abnormal heart electrical flow leads to abnormal heart beats.
Disease and abnormality in the electrical pathways may cause normal rhythm (called sinus rhythm) to be disrupted, prompting the heart to beat too slowly (bradyarrhythmia or bradycardia), too quickly (tachyarrhythmia, tachycardia, or fibrillation), or erratically.
Unlike normal heart rhythm, in atrial fibrillation the upper chambers of your heart (the atrias) simply quiver at approximately 400-600 beats per minute. This shivering motion takes over the normal and regular beating of the heart (which is about 60-100 beats per minute) and makes the lower main pumps (the ventricles) beat as fast it can keep up (typically can be as fast as 180 to 220 beats per minutes).
When your heart beats this fast, it does two main things:
- It makes the heart rhythm irregular and can be uncomfortably fast, and
- It makes the blood flow slows and pool in the top chambers.
The fast and irregular heart rhythms are what contribute to the associated symptoms and problems of atrial fibrillation:
- Shortness of breath
- Fatigue
- Palpitations
- Lightheadedness
- Perspiration
- Chest pain, and
- Symptoms associated with stroke and /or congestive heart failure.
When the heart is in atrial fibrillation, it is often classified by your doctor as:
- Paroxysmal Atrial Fibrillation (self-terminating within one week);
- Persistent Atrial Fibrillation (lasting more than a week, or requires medication/cardioversion);
- Long-standing Atrial Fibrillation (lasting more than one year);
- Permanent Atrial Fibrilltion (not a candidate for curative therapy).
These classifications matter because atrial fibrillation is not simply "one disease."
While each type of atrial fibrillation commonly has the top chamber quivering at very fast rate, they can be very different in terms of how it is initiated and sustained based on the abnormal triggers in the heart or it can be attributed to the actual diseased atrial chambers (enlargement, fibrosis).
In another word, the paroxysmal AF that comes and goes likely is caused by "triggers" or "hot spots." Permanent AF does not depend on these "triggers" to start them, since the atria may be so diseased already and will be difficult to maintain normal rhythm. This may have significant contribution on how the atrial fibrillation is treated.
Curiously, some people may not even feel it at all. It is not clear why some can feel their heart irregularities and others cannot, but doctors worry about those who can not feel the irregularities because the first visible sign may be heart failure or stroke.
In the past decade, researchers have discovered that what initiates or starts the abnormal heart rhythm is actually a group of abnormal heart muscles that connect the heart's top chambers (the atria) to the lungs. After the heart has been in atrial fibrillation for many years, the top chambers often become very diseased and scar tissue may develop and become stretched. The atrium itself may lose the ability to keep itself in normal rhythm. The sooner normal rhythm can be restored, the better the chance of the heart staying in normal rhythm.
Why does AFib occur?