Chest X-ray: A chest X-ray is usually done only is suspected or if other cardiac conditions are suspected (particularly congestive heart failure.) This may reveal an underlying problem in the lungs or the blood vessels in the chest. In particular, if an underlying pneumonia is suggested, treating the underlying infection will probably fix the AFib.

Transesophageal echocardiogram (TEE): Transesophageal echo is a diagnostic modality in which an ultrasound probe is placed in the esophagus similar to an endoscope and the cardiac anatomy is assessed. A normal echocardiography (transthoracic or TTE) has a low sensitivity for identifying thrombi (blood clots) in the heart. If this is suspected - e.g. when planning urgent electrical cardioversion - a transesophageal echocardiogram (TEE) is preferred. The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. This structure, located in the left atrium, is the place where thrombus most commonly is formed in the setting of atrial fibrillation or flutter. TEE has a very high sensitivity for locating thrombus in this area and can also detect sluggish bloodflow in this area that is suggestive of thrombus formation. If no thrombus is seen on TEE, the incidence of stroke immediately after cardioversion is performed is very low. This diagnostic modality is often used prior to a planned cardioversion or introduction of an antiarrhythmic drug to convert a patient from AFib to sinus rhythm.

Transtelephonic monitor: When you develop symptoms of atrial fibrillation, a strip of your current heart rhythm can be transmitted to your doctor's office over the telephone using a monitor with two bracelets or by placing the monitor against your chest wall.

Event monitor (also called an external loop recorder): If the episodes are too infrequent to be detected by Holter monitoring with reasonable probability, then the patient can be monitored for longer periods (e.g. a month) with an ambulatory event monitor. A monitor that is worn for about a month or more for patients who have less frequent arrhythmia episodes and symptoms. Electrodes (sticky pads) are placed on the skin of your chest. Wires are attached from the electrodes to the monitor. The patient presses a button to activate the monitor when symptoms occur. The device records the electrical activity of the heart several seconds before and after the event. The patient then transmits the device's recorded information over a telephone line to the doctor's office for evaluation.

Exercise stress testing: Some individuals with atrial fibrillation do well with normal activity but develop shortness of breath with exertion. It may be unclear if the shortness of breath is due to a blunted heart rate response to exertion due to excessive AV node blocking agents, a very rapid heart rate during exertion, or due to other underlying conditions such as chronic lung disease or coronary ischemia. An exercise stress test will evaluate the individual's heart rate response to exertion and determine if the AV node blocking agents are contributing to the symptoms. This may also be used to evaluate myocardial perfusion in conjunction other tests.