Tests used to diagnose an arrhythmia include:

Electrocardiogram (EKG)

An EKG is the most common test used to diagnose an arrhythmia. During an EKG, electrodes that detect the electrical activity of your heart record the timing and duration of your heartbeat. This test can show how quickly the heart is beating and its rhythm, as well as the strength and timing of the electrical signals as they pass through the heart.

Holter Monitor

An EKG is conducted in a hospital or doctor’s office, but in some cases, your doctor may want to monitor your heart’s electrical activity for an extended period of time. (Your symptoms may also be so sporadic you are unable to stay in a doctor’s office or hospital long enough to detect one.) In that case, you may be asked to wear a portable EKG, known as a Holter monitor. This monitor can be worn for several days, and it records your heart’s activity continuously.

Event Monitor

Like a Holter monitor, an event monitor will test your heart rate while allowing you to leave your doctor’s office or the hospital and carry on with your routine. The event EKG monitor only begins recording when you start having symptoms of an arrhythmia. (In most cases, you tell the monitor when to begin recording.) This will allow your doctor to see your heart’s rhythm only at the time of the symptoms.

Transthoracic Echocardiogram (TTE)

An echocardiogram uses noninvasive sound waves to produce an image of your heart so your doctors can see how the chambers and valves are functioning. This image is produced by placing a sonography probe on the chest and taking several pictures of the heart through the chest wall.

Transesophageal Echo (TEE)

While a TTE sends ultrasound waves through the front of your body to produce an image, a TEE sends ultrasound waves from your esophagus. This allows your doctor to see the back of your heart and to better visualize the valvular structures of the heart. To do this test, however, your doctor will have to sedate you so he can run a tube down your throat to best visualize the heart.

CT Scan or MRI

Cardiac computerized tomography (CT) or magnetic resonance imaging (MRI) tests can detect heart problems and potential arrhythmias with noninvasive scans. In a CT, you lie on a table inside a round machine. The machine rotates around your body and collects X-rays of your heart and chest. In an MRI, you lie on a table inside a tube-shaped machine. A magnetic field aligns atomic particles in your body’s cells, producing signals that create images of your heart.

Blood Tests

Your doctor may want to check the levels of electrolytes—such as potassium, sodium, and calcium—present in your blood. He or she may also want to check your thyroid hormone. If any of these levels are too low or too high, they can cause arrhythmias.

Stress Test

Some arrhythmias are easier to detect when your heart is working harder than when it is at rest, such as during exercise. Your doctor may have you exercise in a controlled environment to increase your heart rate. During your period of activity, your heart is monitored by an EKG. If you’re unable to exercise or have a difficult time doing it, he may give you a pill that will stimulate your heart to achieve heart rate levels similar to that of exercise.

Tilt Table Test

If one of your symptoms is fainting, your doctor may use a tilt table to check for a possible arrhythmia. In this test, you lie flat on a table. The table is then tilted 90 degrees to a standing position. Your doctor will watch your heart, nervous system, blood pressure, and EKG readings as the table moves you up and down from flat to standing.

Coronary Angiography

A thin, flexible tube (called a catheter) is inserted into a blood vessel either in your arm, upper thigh (groin), or neck. Using a special dye and X-ray machine, your doctor can watch the flow of blood through your heart and blood vessels, looking for any possible blockages or leaks.

Electrophysiologic Testing and Mapping

Much like with the coronary angiography, electrophysiologic testing and mapping uses a thin, flexible catheter to map the inner workings of your heart. But in this case, electrodes on the catheter stimulate the heart, and a machine records the spread of these impulses as they travel through the heart. This helps your doctor find where the impulses may be blocked or where short circuits may exist.

Implantable Loop Recorder

An implantable loop recorder is placed under the skin of your chest where it can record and detect any abnormal heart rhythm. This device is particularly helpful if your symptoms don’t occur frequently.