Once your doctor diagnoses an arrhythmia through your symptoms or an examination, he or she will need to determine where it originates and whether it requires treatment; that is, whether it is causing symptoms or putting  you at risk for more serious problems in the future.

The electrocardiogram  is a very important tool that  your  doctor  uses to  diagnose  and  study  your  arrhythmia. The ECG  records and measures the path and timing of your heart’s electri- cal impulses from their origin in the sinoatrial node, through the atria, through the atrioventricular node, and into and through the ventricles. However,  the  standard  ECG  can only  record  the  electrical  activity that takes place during the short time that the machine is hooked up to you.

Ambulatory  ECG  methods  enable  your  doctor  to  study  longer periods of the heart’s activity while you go about your normal routine. Ambulatory  ECGs  are available in the form of a Holter monitor , which you wear for 24 to 48 hours  and which provides a continuous readout.  Your doctor  compares the ECG  recordings  with your account  of your activities and symptoms to see if an arrhythmia is occurring,  how often it occurs, and how it relates to the daily log of your activities. Also, the effectiveness of any antiarrhythmic medica- tions you may be taking can be monitored. However,  if your arrhyth- mia  is very infrequent, 48  hours  of Holter monitoring may  not capture  it.

An event monitor   is another  ambulatory  ECG,  one that allows for longer  recording—as  long as 30 days. You activate the device yourself if you sense symptoms. The monitor’s recording system is “looped” to continuously  record and erase, so that when you activate it, it can retrieve data from 1 to 4 minutes prior to that time.

Your doctor may want to order exercise stress testing  to see if an arrhythmia is brought  on by exercise. If you have had faint- ing spells, you may be asked to have a tilt-table  study  to observe how your heart responds to a change in position. This informa- tion  helps  your  doctor  determine how to  prevent  fainting  episodes. Echocardiography  may also be used to determine if there is structural  heart disease that may be causing arrhythmias.

Electrophysiologic studies  are done in a hospital setting to more speci?cally study an arrhythmia,  test the effect of medications, and perform  some treatments  such as catheter  ablation. Electrophysio- logic studies are generally done by threading catheters through  the veins into  your heart  in order  to record  electrical signals and stimulate  the heart to induce an arrhythmia, to provide more precise information about your heart rhythms. Because the test requires that catheters are placed in your veins, it is described  as an invasive study. However,  with proper preparation,  electrophysiology studies can be performed with little or no discomfort  and are among the safest of all invasive tests. Also, impor- tantly, if possible, some arrhythmias are treated or cured at the same sit- ting during your electrophysiologic studies, with only a small risk to you.

Electrophysiology studies  require  taking  periodic  X-rays via ?uo- roscopy during the procedure to determine where the catheter is within the heart. In some cases, transesophageal echocardiography may be used.

Substances That Can Affect Heart Rhythm

Thousands of substances have the potential to affect the electrical signals that stimulate your heartbeat. The impact of any one of them on you can range from harmless to severe. If you are diagnosed with a heart arrhythmia, be aware of your own exposure to some of these substances, and talk to your doc- tor about how they might be affecting your symptoms, the effects of your med- ications, or your overall heart health.
• Caffeine in coffee, soft drinks, tea, or chocolate
• Alcohol
• Tobacco, including secondhand smoke
• Diet pills
• Some over-the-counter cough and cold remedies (especially those with pseudoephedrine)
• Some herbal remedies (such as ephedra or ephedrine)
• Prescription drugs (such as antianxiety, antipsychotic, or antiarrhythmic medications)
• Bronchodilators, whether prescription or over-the-counter
• Automobile emissions
• Industrial pollution
• Paint thinners
• Propane gas
• Hazardous substances in the workplace (such as carbon monoxide)