Electrocardiogram (EKG or ECG) is a routine cardiac investigational procedure which can give us valuable information on the rhythm of your heart, its electrical conduction, muscle mass, presence of arrhythmia, ischemia or infarction and even electrical disturbance and drug effects. An ECG works because the same electrical currents that circulate in your heart can actually be picked up as signals from your chest. If your atrial fibrillation is "chronic", it is readily seen on the ECG. The wavy baseline replacing the distinct atrial contractions (representing fibrillating activity in the atria) with the irregular, often rapid ventricular response makes atrial fibrillation a fairly easy arrhythmia to diagnose.

If your atrial fibrillation is "paroxysmal", you may have sporadic episodes of atrial fibrillation from as often as a few times a day to as rarely as once every few weeks to even months. An EKG is not particularly helpful if you happen to be in normal sinus rhythm at the time of the recording.

To capture the arrhythmia so that it can be treated properly, your doctor may elect to place you on an ambulatory or Holter monitor. This is a small box that records your electrocardio-gram continuously for 24 or more hours. The box is attached to your body with wires that connect to electrodes placed on your skin. You will be given a diary card, on which you should write the time and description of any symptoms or other significant activities. After you return the box, the recording is played back into a special analysis machine and your rhythm can be interpreted.

An event recorder is the more appropriate recording device if your episodes of atrial fibrillation are even less frequent and cannot be captured in a given 24 hour recording. This recorder can be carried in your pocket or a purse and can be lent to you for two to four weeks at a time. At the onset of your symptoms, press the device against your chest and push the button which starts recording your heart rhythm. Alternatively, some event records are worn on your wrist like a watch. In either case, you dial a telephone number to transmit the recorded rhythm to a receiving station. The receiving station prints out the copy of the rhythm, which can be interpreted by your doctor or a trained technologist.

Echocardiogram, often referred to as an "echo", is a non-invasive procedure that gives us very important information about the structure of the heart. It uses an ultrasound to image the moving heart muscle, the structure and the functions of the heart valves, and the flow of blood inside the heart and vessels.

The transducer placed on the chest transmits and receives the reflected ultrasound, thus creating the image. Being able to view the heart in this way is especially useful in the diagnosis and grading of the severity of valvular and congenital heart diseases, measuring the size of the heart chambers, and assessing the presence of clots. To get an even better view of the heart, especially the left atrium, the probe is sometimes placed in the esophagus and imaging is effectively performed from the back of the heart. This procedure, called transesophageal echocardiography or "TEE", is usually done under mild sedation and the throat is made numb with an anesthetic spray.

Chest X-ray is another diagnostic test which is sometimes included in the work-up phase of atrial fibrillation. The X-ray gives us information about the size and the configuration of the heart, great vessels, and the lungs. Some contributing factors to arrhythmias, such as structural abnormalities in your heart or an acute infection or a blood clot in your lung, can be initially identified with this simple test. Certain blood tests also provide important information about thyroid function, electrolyte balance, and any ongoing heart muscle damage, which are all potentially correctable contributing factors in arrhythmias.

Other tests which are sometimes used to obtain information about the heart are cardiac magnetic resonance (MRI) and chest computed tomography (CT) scan. Magnetic source imaging measures the magnetic field your heart generates, which can serve as a key to the source of the arrhythmia.

At UCSF, we are exploring the use of other, more advanced, diagnostic tools. For example, the recognition of "focal triggers" at the start of atrial fibrillation may have very important implications for treatment, as discussed below. We are developing ways to distinguish these various types of atrial fibrillation in ways not possible using standard ECGs. One such test is called body surface mapping. This test is like an ECG, but it uses 64 leads or electrodes. This allows us to better understand where an arrhythmia might originate. Another tool is an esophageal recording. In this test, the patient swallows a small electrode or a tube that sits comfortably in the esophagus. The esophagus is located right behind the left atrium, which is an important possible source of atrial fibrillation triggers. This test allows us to pick up much more specific signals about the electrical activity in this area than the standard recordings that measure the overall electrical activities of the heart. The esophageal recording may be done briefly, or the electrode may be hooked up to a Holter monitor for longer recording period. These wires can be worn quite comfortably for a day or more.

In addition to all of these non-invasive tests, the ultimate test of the heart's electrical system involves placing small tubes or catheters into the heart under X-ray guidance. This is known as a cardiac electrophysiology (EP) study. During an EP study, detailed recordings of the electrical signal in your heart can be obtained. Think of it as recording an ECG from directly inside the heart. We can track how the waves move through your heart, a process called mapping. We can also find out if your heart is prone to certain types of arrhythmias by stimulating the heart at various rates and from various sites. In many cases, we can directly administer treatment through the same catheters. For example, catheter ablation is a method wherein we can make a small burn at a specific site and actually cure many types of arrhythmias. Some cases of atrial fibrillation can now be treated with catheter ablation.