Technical Problems

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Author(s) J.S.S.G. de Jong
Moderator J.S.S.G. de Jong
some notes about authorship

Lead reversals

Lead switches are a common mistake when ECGs are made and can lead to wrong diagnoses. Common mistakes are:

  • Left-right arm reversals lead to a negative complex in lead I with a negative P wave in lead I. They are one of the most common causes of right axis deviation on the ECG!
  • Arm-foot switches lead to a very small or 'far field' signal in leads II or III.
  • Chest lead reversals lead to inappropriate R wave progression (increase- decrease-increase) and are often easily recognized.

Therefore any right axis or small signal in an extremity lead should be reason enough to check lead positioning. A previous ECG can be very helpful.

More specific patterns with every lead reversal:

  • right leg and right arm:
    • diminished signal in lead II
  • right and left arm electrodes:
    • reversal of leads II and III
    • reversal of leads aVR and aVL
  • left arm and left leg:
    • reversal of leads I and II
    • reversal of leads aVR and aVF
    • inversion of lead III
  • right arm and left leg:
    • inversion of leads I, II and III
    • reversal of leads aVR and aVF

It is possible to distinguish lead reversal and dextrocardia by watching the precordial leads. Dextrocardia will not show any R wave progression in leads V1-V6, whereas lead reversal will.


Artifacts (disturbances) can have many causes. Common causes are:

  • Movement
  • Electrical interference