When a patient is actively having an episode of atrial fibrillation, it's easy to diagnose through a simple electrocardiogram (ECG), which is a visual test that will reveal the diagnosis in virtually all such patients.
However, many patients with atrial fibrillation have transient episodes (called " paroxysmal atrial fibrillation,") lasting from minutes to hours. These patients will generally complain of sudden episodes of palpitations and perhaps shortness of breath. If the episode has ended by the time they receive medical attention, no sign of atrial fibrillation will be found.
In these patients, some form of outpatient monitoring is necessary to make a diagnosis. (In other words, patients wear a portable monitor continuously for periods of up to several weeks, until an episode of atrial fibrillation is "captured.") This can usually be accomplished with a cardiac event monitor.
