Atrial fibrillation, also sometimes called A-fib, is usually diagnosed with an electrocardiogram (ECG). An ECG is a noninvasive diagnostic procedure that uses electrodes taped to the skin on the chest to measure the electrical activity within the heart. This information creates a tracing, which can be printed on paper or viewed on a monitor. In atrial fibrillation, the irregular quivering beats of the heart's upper chambers create a characteristic tracing.
Occasionally atrial fibrillation is noticed incidentally on an ECG or other heart test. More commonly, doctors order an ECG because a person is having symptoms that could be caused by atrial fibrillation, such as palpitations, a racing heartbeat, dizziness, or shortness of breath. Doctors (and sometimes patients) may also have noticed that the pulse in the wrist or neck is irregular.
Doctors usually follow up a new diagnosis of atrial fibrillation with additional tests to look for an underlying cause or trigger. These tests may include blood tests, an echocardiogram (an ultrasound of the heart), and/or a chest X-ray.