Dear Doctors: I am a 47-year-old woman in good health. I exercise regularly and eat a healthy diet. At my physical, I was surprised when my doctor said I have A-fib. I have never felt anything wrong with my heart, so I am confused. Can you please explain A-fib?
Dear Reader: You are asking about a heart condition called atrial fibrillation. Often referred to simply as A-fib, it is a type of heart arrhythmia. The heartbeat we rely on to circulate blood throughout the body is made up of a precise series of rhythmic contractions. This includes the timing of the heartbeats, and the slight pause between them. If any element of this series goes awry for even a short period of time, it is known as an arrhythmia.
To better understand, we should start with a bit of anatomy. A healthy adult heart is roughly the size of a clenched fist and resembles an inverted pear. It is divided into four chambers, two above and two below. The lower chambers are known as the left and right ventricles. The two on top, which are the ones involved in the arrhythmia you have been diagnosed with, are called the left and right atrium.
The right atrium and right ventricle work together to receive the blood that has just traveled throughout the body and move it into the lungs. There, it gets topped off with oxygen. The left atrium and left ventricle work together to receive the now-oxygen-rich blood exiting the lungs and to send it off to the tissues of the body.
When someone has atrial fibrillation, it means the two upper chambers of the heart have ceased to function properly. It occurs due to a malfunction in a cluster of cells in the right atrium, known as the sinus node, which send out the electrical signals that regulate heart rhythm.
Rather than producing the strong and coordinated contractions needed to move blood through the heart valves and into the ventricles, the atria behave erratically. This can include beating too fast, making quivering and incomplete contractions, failing to pause between contractions and beating out of sync with the ventricles below. The result is a chaotic heartbeat that stalls the flow of blood through the heart. It can cause blood to pool in the atria, which can clot. This, in turn, raises the risk of a stroke. In 15% to 20% of strokes, A-fib is a factor.
As has happened with you, not everyone with A-fib develops symptoms. When they do manifest, symptoms can include a fast and irregular pulse, a fluttery sensation in the chest, general fatigue, unusual fatigue when exercising, shortness of breath, dizziness and weakness. Reduced blood flow in the heart can cause angina, which is chest pain or a sensation of pressure.
The fact you are not experiencing symptoms does not mean this diagnosis can be ignored. Treatment typically includes identifying the reason for the condition, reducing stroke risk and using medications or appropriate procedures to restore normal heart rhythm. It would be wise for you to follow up this diagnosis with a cardiologist.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
