January 14, 2011
Dear Mayo Clinic:
I suffer from atrial fibrillation. Are my chances of getting a heart attack higher?
Your risk of a heart attack is not increased due to atrial fibrillation, a rapid and irregular heartbeat that can cause symptoms requiring medical attention. The condition does not cause a heart attack. However, atrial fibrillation can lead to other serious complications, so it needs to be treated promptly and monitored closely.
During atrial fibrillation, the heart's two upper chambers (atria) beat chaotically and irregularly, out of coordination with the two lower chambers (ventricles). Because of the uncoordinated heartbeat it produces, atrial fibrillation causes your heart to pump less effectively than normal. The result is that the heart sends less blood out to your body with each beat. This can cause a variety of symptoms, including decreased blood pressure, light-headedness, weakness and shortness of breath.
Occasionally, the rapid heart rate associated with atrial fibrillation can result in chest pain or discomfort (angina) because of reduced blood flow to the heart muscle. People who have pre-existing heart disease are particularly susceptible to this symptom of atrial fibrillation. Angina can be hard to distinguish from other types of chest pain, so if you experience chest pain, it is important to seek medical attention right away.
Although it can cause chest pain and other symptoms that are similar to a heart attack, atrial fibrillation doesn't lead to a heart attack. Instead, a heart attack (myocardial infarction) occurs when the coronary artery, which supplies blood to the heart, becomes blocked, depriving the heart of vital blood and oxygen.
The blockage is most commonly due to narrowing of a coronary artery that is caused by a buildup of cholesterol (plaques), a condition known as atherosclerosis. Those plaques can break open and, when they do, a blood clot forms at the site of the plaque rupture. If the clot is large enough, it can completely block the flow of blood through the artery, causing a heart attack.
Atrial fibrillation doesn't create the conditions that lead to a heart attack. But a heart attack may cause atrial fibrillation. If a coronary artery involved in the heart attack normally supplies blood to the atria, the lack of blood flow may damage the atrial tissue and atrial fibrillation can result.
Even though your risk of a heart attack is not increased due to atrial fibrillation, your risk of other serious complications, such as stroke and heart failure, does go up because of this condition. The irregular heart rhythm of atrial fibrillation can cause blood to pool in your atria and form clots. Although those clots won't lead to a heart attack, one of them could dislodge from the atria and travel through your bloodstream to your brain. There it might block blood flow, causing a stroke.
The risk of stroke in atrial fibrillation is higher as you get older. It's also higher in people who have high blood pressure, diabetes, or a history of heart failure or previous stroke. If you have atrial fibrillation, medications such as blood thinners can significantly lower your stroke risk.
Heart failure can also be a concern, particularly if atrial fibrillation is not well controlled. The reason for concern is that atrial fibrillation with an uncontrolled rapid heart rate can weaken the heart muscle, eventually making your heart chronically unable to circulate enough blood to meet your body's needs.
Talk to your doctor about the risks associated with atrial fibrillation and what you can do to reduce those risks.
ā Stephen Hammill, M.D., Cardiovascular Diseases, Mayo Clinic, Rochester, Minn.