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More About Arrhythmia

An arrhythmia occurs when there is a problem with the electrical system that is supposed to regulate a steady heartbeat. With an impaired electrical system, your heart may beat too fast, too slow, or irregularly.

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Diagnosing Arrhythmia

There are several tests that may be used to diagnose arrhythmias. Some of these include:

  • Electrocardiogram (ECG). An electrocardiogram is a measurement of the electrical activity of your heart. By placing electrodes at specific locations on your body (chest, arms, and legs), a graphic representation, or tracing, of the electrical activity can be made as the electrical activity is received and interpreted by an ECG machine. An ECG can show the presence of arrhythmias, damage to your heart caused by ischemia (lack of oxygen to the heart muscle), or myocardial infarction (MI, or heart attack), a problem with one or more of the heart valves, or other types of heart conditions.

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There are several variations of the ECG test:

  • Resting ECG. For this procedure, the clothing on your upper body is removed and small sticky patches called electrodes are attached to your chest, arms, and legs. These electrodes are connected to the ECG machine by wires. The ECG machine is then started and records your heart's electrical activity for a minute or so. You are lying down during this ECG.
  • Exercise ECG, or stress test. You are attached to the ECG machine as described above. However, rather than lying down, you exercise by walking on a treadmill or pedaling a stationary bike while the ECG is recorded. This test is done to assess changes in the ECG during stress, such as exercise.
  • Signal-averaged ECG. This procedure is done in the same manner as a resting ECG, except that your heart's electrical activity is recorded over a longer period of time, usually 15 to 20 minutes. Signal-averaged ECGs are done when arrhythmia is suspected, but not seen on a resting ECG. The signal-averaged ECG has increased sensitivity to abnormal ventricular activity called "late potentials." Signal-averaged ECG is used in research and seldom used in clinical practice.
  • Electrophysiologic studies (EPS). A nonsurgical but invasive test in which a small, thin tube (catheter) is inserted into a large blood vessel in your leg or arm and advanced to your heart. This lets your doctor find the site of the arrhythmia's origin within your heart tissue. Your doctor is then able to determine how to best treat it. Sometimes, your doctor can treat the arrhythmia by doing an ablation at the time of the study. 
  • Holter monitor. A continuous ECG recording done over a period of 24 or more hours. Electrodes are attached to your chest and connected to a small portable ECG recorder by lead wires.  Holter monitoring may be done when an arrhythmia is suspected, but not seen on a resting ECG. Arrhythmias may be transient in nature and not seen during the shorter recording times of the resting ECG. You go about your daily activities, except those that cause an excessive amount of sweating. This could cause the electrodes to become loose or fall off during the procedure. These activities include taking a shower or swimming. 
  • Event monitor. This is similar to a Holter monitor, except that you start the ECG recording only when you feel symptoms. Event monitors are typically worn longer than Holter monitors. You can remove the monitor to shower or bathe. 
  • Mobile cardiac monitoring. This is similar to both a Holter and event monitor. The ECG is monitored constantly to allow for detection of arrhythmias, which are recorded and sent to your doctor regardless of whether you have symptoms. You can also start recordings yourself when you have symptoms. These monitors can be worn up to 30 days. 
  • Implantable loop recorder. This is a miniature heart recording device that is implanted underneath the skin overlying your heart. It can record the heart rhythm for up to 2 years and it useful in diagnosing intermittent or rarely occurring arrhythmias.