Perhaps you told your doctor you could feel your heart pounding in your chest, were short of breath, or felt very tired. Maybe you didn't have any symptoms at all. Either way, your doctor ordered tests that determined you have atrial fibrillation.
In atrial fibrillation the two upper chambers of the heart, the atria, start quivering instead of pumping efficiently and regularly. The heartbeat becomes irregular and faster. Some people find this arrhythmia frightening or otherwise distressing; others do not feel it at all. Either way, untreated atrial fibrillation is a major risk factor for stroke.
"Right now, one in every four strokes in people over age 80 is attributed to atrial fibrillation. These numbers could rise, since the number of people diagnosed with atrial fibrillation is expected to increase over the next 20 years as our population ages," says Dr. Peter Zimetbaum, a heart rhythm specialist at Harvard-affiliated Beth Israel Deaconess Medical Center.
In atrial fibrillation, the electrical signals coming from the heart's upper chambers (atria) are rapid and erratic [A]. This causes the heart to contract in a fast, uncoordinated, chaotic fashion.
What causes atrial fibrillation?
About 80% of people with atrial fibrillation have an underlying condition such as high blood pressure, coronary artery disease, or cardiomyopathy. A sudden heart attack, a blood clot in the lungs (pulmonary embolism), or a dangerously overactive thyroid gland can trigger an arrhythmia. Atrial fibrillation also occurs in 40% of people following heart or lung surgery, and in people who are obese or who have sleep apnea, a condition that causes them to stop breathing periodically during sleep.
It is not known why an arrhythmia develops in some people but not others. "In truth, our understanding of atrial fibrillation is incomplete. It is likely a complex and varied disease," says Dr. Zimetbaum.
Some people experience occasional episodes of atrial fibrillation that resolve by themselves. In others, the episodes last long enough that something must be done to stop them. Atrial fibrillation can sometimes be continuous and difficult to stop. These distinctions are important, because they help determine the treatments that are likely to work best.
Why treat atrial fibrillation?
There are two reasons to treat this arrhythmia:
to stop symptoms, such as shortness of breath or other discomfort
to prevent a blood clot from forming in the heart and traveling to the brain, where it can cause a stroke.
Treating atrial fibrillation requires drugs or procedures to bring the heart rate and rhythm under control and to prevent blood clots from developing.
Controlling rate and rhythm
The first step is to try to lower your heart rate with a beta blocker or calcium-channel blocker. The drug your doctor prescribes will depend on the underlying reason for your arrhythmia and the type of side effects the drug may produce.
Sometimes, a drug to make your heart rhythm more regular (antiarrhythmic drug) may be needed to reduce the frequency of episodes and symptoms. These drugs may have side effects and cannot be used in certain people. That's why many doctors try rate-control drugs first.
When drugs cannot be tolerated or fail to produce the desired results, an electrophysiologist (a cardiologist specializing in arrhythmias) may need to perform a procedure called catheter ablation, which is performed under anesthesia. A thin, flexible tube (catheter) is inserted in a vein and advanced to the heart. The electrical cells responsible for creating the arrhythmia are located and destroyed with heat or cold. Although this generally restores a proper heart rhythm, atrial fibrillation often recurs later. Overall, catheter ablation is only about 70% effective, even after several procedures, and may not be permanent.