Atrial fibrillation is the most common cardiac arrhythmia. With a normal heart rhythm, organized and predictable electrical impulses originate from the sinus node. With atrial fibrillation, multiple chaotic electrical signals originate all over the atria at a very fast rate (about 300 - 600 per minute). The ventricles receive these signals and contract separately from the atria. This process results in an irregular and usually a fast heart rate.
A common heart rate for a patient with untreated atrial fibrillation is between 80 - 160 beats per minute. Since the atria quiver instead of contracting normally, the amount of blood pumped out of the heart with each beat is decreased.
Symptoms of Atrial Fibrillation
Patients with symptomatic atrial fibrillation typically experience palpitations, weakness, lightheadedness, dizziness, fainting, fatigue or chest discomfort. Some people are asymptomatic and have no symptoms at all.
Causes of Atrial Fibrillation
Normally, the heart's electrical signal travels down a specific path to initiate a contraction or "beat." Usually, atrial fibrillation begins as a result of something that damages or changes the structure of the heart. Here are some examples:
- Coronary artery disease
- Hypertrophy (enlarged heart)
- Cardiomyopathy (weakening of the heart muscle)
- Congestive heart failure
- Pulmonary embolus
- Valve disease
- Excessive alcohol intake
The doctor will order an EKG to check for atrial fibrillation. If present, the tracing will have a chaotic, often fast and irregular rate. However, the EKG only shows what is happening with the heart at the time of the tracing.
Frequently patients spontaneously go in and out of atrial fibrillation, so the physician may want to follow a tracing for a longer period of time. Monitors can be worn for up to 30 days at a time to evaluate for paroxysmal (intermittent) atrial fibrillation.
Additionally, the patient may be scheduled for a cardiac catheterization if the doctor suspects coronary artery disease.
During atrial fibrillation, blood tends to pool as the atria quiver instead of contract in an organized way. This predisposes the patient to the formation of clots. Those clots can dislodge and travel to the brain. Atrial fibrillation patients are at higher risk for stroke over patients without the condition.