Atrial Fibrillation

Diagnosis

In atrial fibrillation, the electrical signals in the atria (upper chambers of the heart) are chaotic and the electrical impulses reach the ventricles (lower heart chambers) often at irregular intervals, causing a fast and irregular heartbeat. A comprehensive diagnosis at Mayo Clinic helps to determine the severity of the atrial fibrillation and its potential to cause more serious conditions, such as stroke.

To diagnose atrial fibrillation, the patient may be asked about or tested for conditions that may trigger the fibrillation, such as heart disease or a thyroid gland problem. Several tests may be given to better understand the cause of the arrhythmia.

Some tests are performed at the clinic:

Stress Test
Atrial fibrillation may be triggered or worsen when the patient is exercising. During a stress test, the patient may exercise on a treadmill or stationary bicycle, with close monitoring by an ECG of heart activity. The test is intended to actively induce an irregular heartbeat while the patient is being monitored. The test may involve use of a drug to stimulate the heart instead of exercise. This may be particularly helpful to patients who have difficulty exercising. The stress test can also be used to detect coronary artery disease.

Electrocardiogram (ECG)
In this test, electrodes (sensor patches with wires attached) are placed on the patient's skin to measure the electrical impulses given off by the heart. The ECG measures the timing and duration of each electrical phase in the heartbeat.

Echocardiogram (Doppler Echocardiogram)
This test uses sound waves to produce detailed images of the patient's heart. Through a handheld device (transducer) on the patient's chest, sound waves bounce off the heart and are reflected to produce video images of the heart's size, structure and motion. The echocardiogram can also be used to measure the heart's blood volume and the speed and direction of blood flow through the heart.

Blood Tests
These may help rule out thyroid problems or other blood chemistry abnormalities that may lead to atrial fibrillation.

In addition, the heart may be monitored during regular activity.

Holter Monitor
A Holter monitor is a portable ECG device that the patient wears for a day or more to record the heart's electrical activity during the patient's daily routine.