Electrocardiography (ECG)
Holter monitor (continuous ambulatory electrocardiographic monitor)
Transtelephonic monitor (event recorder)
Treadmill testing
Tilt table studies
Electrophysiologic testing
Esophageal electrophysiologic procedure
Transthoracic echocardiography (TTE)

Electrocardiography (ECG)
An arrhythmia is considered documented if it can be recorded on an electrocardiogram (ECG or EKG.) This is the standard clinical tool for diagnosing arrhythmias. It records the relative timing of atrial and ventricular electrical events. It can be used to measure how long it takes for impulses to travel through the atria (the heart's upper chambers), the atrioventricular (AV) conduction system and the ventricles (the heart's two lower, pumping chambers). Because of the fleeting nature of arrhythmias, a person who complains of symptoms that suggest arrhythmia may often have an ECG that appears normal. Electrocardiographic techniques are passive; they can only record an arrhythmia if it occurs spontaneously while the ECG is being taken.

To conduct an ECG, the healthcare professional places small patches or stickers called electrodes on different parts of the body. One is put on each arm and leg and several across the chest. They don't hurt. With various combinations of these electrodes, different tracings of the heart's electrical activity can be made and permanently recorded on paper or in a computer.

Three major waves of electric signals appear on the ECG. Each one shows a different part of the heartbeat.

• The first wave is called the P wave. It records the electrical activity of the atria (the heart’s upper chambers).
• The second and largest wave, the QRS wave, records the electrical activity of the ventricles (the heart’s lower chambers).
• The third wave is the T wave. It records the heart's return to the resting state.

Doctors study the shape and size of the waves, the time between waves and the rate and regularity of beating. This tells a lot about the heart and its rhythm.

Watch an animation of an electrocardiogram

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Holter monitor (continuous ambulatory electrocardiographic monitor)
Suspected arrhythmias sometimes may be documented by using a small, portable ECG recorder, called a Holter monitor (or continuous ambulatory electrocardiographic monitor). This can record 24 hours of continuous electrocardiographic signals. While an ECG is sort of a 12-second "snapshot" of the heart's electrical activity, the Holter monitor is more like a "movie."

As with an ECG, electrodes are taped to the chest. The wires are connected to a portable, battery-operated recorder that can run for 24 to 48 hours. You can do most normal activities while being tested. You may need to keep a diary or log of your activities and symptoms. 

At the end of the measurement period, the recorder’s tape or memory is analyzed on a computer that rapidly identifies rhythm disturbances that occurred while you were wearing the monitor. The diary helps your healthcare professional see how your activities or symptoms correspond to recorded events in your heart.

For suspected arrhythmias that occur less frequently than every day, your doctor might have you wear an event monitor.

See an illustration of a Holter monitor
Download our printable Holter monitor diary form

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Transtelephonic monitor (or event recorder)
Sometimes arrhythmia symptoms happen infrequently or pass so quickly that you can't get to a doctor or hospital. In these cases, a transient event monitor may be used. This small recorder is sent home with you for a month or two. When you have symptoms, attach the recorder with bracelets, finger clips or patches under the arms. The ECG will be recorded and stored. When it's convenient, you can transmit the ECG by phone to your cardiologist to be analyzed.

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Treadmill testing
This is an option that provokes arrhythmias and makes their diagnosis (and thus their proper treatment) easier. A treadmill test may be used for people whose suspected arrhythmias are clearly exercise-related. It is important to know if exercise makes an arrhythmia worse. To test this, you will walk and run on a treadmill — or ride a stationary bicycle — while your heart rate and rhythm are monitored.

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Tilt table studies
A tilt test may be advised for some people who've had recurrent fainting spells (syncope). This test shows how your heart rate and blood pressure respond to a change in position from lying down to standing up. In this test, an intravenous line (a small plastic tube in a vein) is usually started in case medications need to be given during the test. A catheter also may be placed in the artery to monitor blood pressure from inside the artery. If a cause of the fainting spells is found, medications can be given through the intravenous line to help prevent the episodes.

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Electrophysiologic testing
This method has become extremely valuable for provoking known but infrequent arrhythmias and for unmasking suspected arrhythmias. This procedure is done using local anesthesia. Temporary electrode catheters are placed through peripheral veins (or arteries) into the heart using a fluoroscope. Then these catheters are positioned in the atria, ventricles or both, and at strategic locations along the conduction system. They record cardiac electrical signals and "map" the spread of electrical impulses during each beat, thus showing where the heart block is (AV node vs. His-Purkinje system). This test also shows where tachycardia originates (supraventricular vs. ventricular) far better than an ECG usually does.

The ability to electrically stimulate the heart at programmed rates and induce precisely timed premature beats lets a doctor assess electrical properties of the heart's conduction system. Most significantly, it also triggers latent tachycardia or bradycardia. Induced tachycardias can usually be stopped by rapid pacing via the electrode catheters. Sometimes an externally applied shock may be required if the patient loses consciousness during the tachycardia. Being able to "turn on" and "turn off" tachycardias during electrophysiologic studies allows antiarrhythmic drugs to be tested quickly for effectiveness. This can be done during a single study using intravenous therapy or during short follow-up studies with oral medication. Electrophysiologic testing has been performed safely worldwide; complications only rarely occur.

Watch an animation of an intracardiac electrophysiology study

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Esophageal electrophysiologic procedure
In some situations, your cardiologist may advise doing an esophageal electrophysiologic procedure. This is used to diagnose or treat the type of tachycardia you have. A thin, soft, flexible plastic tube will be inserted into your nostril and positioned in the esophagus (the tube that connects the mouth and stomach). Because the esophagus is close to the heart's upper chambers (atria), an ECG recording there gives more precise information than a regular ECG. An electrical stimulator may be used to make the heart beat faster to try to restart your arrhythmia. This helps your doctor make the right diagnosis.

During this procedure certain medications may be tested to find the most effective one. This procedure also may be done to temporarily stop certain types of arrhythmias.

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Transthoracic echocardiography (TTE)
An echocardiogram uses ultrasound waves to map a picture of the heart, much like sonar is used to study solid objects in the sea. You may only think of ultrasound being used to monitor a baby's growth, but ultrasound waves can also show the heart's size, structure and motion. A technician has you turn on your left side. The technician places some gel on your chest and then moves a transducer over your chest and obtains images of your beating heart.  It's a non-invasive test that's simple, painless and often provides valuable information about a heart with an arrhythmia.

See an illustration of an echocardiogram

This content is reviewed regularly. Last updated 01/15/09.