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A signal average ECG, or "Late Potential Detector" is a microprocessor based electrocardiogram (ECG). This type of ECG provides the cardiologist with knowledge about the potential to have a life threatening heart rhythm. It gives the Baylor Scott & White Cardiology Consultants of Texas doctor different information than a 12 lead ECG.


This is a good screening test for detecting patients prone to sustained ventricular tachycardia (a potential life threatening heartbeat).  If the test does show the potential to have this rhythm, then a more aggressive cardiac evaluation is warranted.  The test itself only takes about 5 minutes.

Before The Test

  • There are no dietary restrictions. 
  • Wear a loose fitting blouse or shirt, with the buttons in the front. Do not wear a one-piece jumpsuit.
  • Do not use lotions or bath oil on your skin. This will prevent the electrodes (sticky patches) from sticking to your skin.

During The Test

  • A trained medical assistant (or nurse) will place six electrodes (small sticky patches) on your chest  and one electrode on your back.  The areas on your chest and back will be cleansed with alcohol and an abrasive pad will be used to ensure good electrode contact.  Men may need to have areas of their chest shaved. 
  • The electrodes are connected by wires to the signal average ECG machine. 
  • You will be lying on your back on an exam table.  Once the test has started, you will be asked to lie very still on the table, while the machine is collecting data for the 3 channel ECG. 
  • The machine will then produce a 3 channel ECG for the BSW​ Cardiology Consultants of Texas doctor to interpret.

After The Test

  • Immediately after the test, the physician can give you a complete interpretation. The presence of a "late potential" has been associated with the potential to have an abnormal heart rhythm. 
  • If the test is abnormal, your doctor may order additional tests.