Technical Problems

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Revision as of 09:43, 14 May 2009 by Odesk1 (talk | contribs) (artifacts)
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Author(s) J.S.S.G. de Jong
Moderator J.S.S.G. de Jong
Supervisor
some notes about authorship

Lead reversals

Right and left arm lead reversal can be distinguished from the (much rarer) dextrocardia by looking at the precordial R wave progression.
Right arm and left leg lead reversal. Lead II now measures the signal between the left and right leg, which is remote from the heart.
A patient with dextrocardia (and previous inferior myocardial infarction)

Sometimes an ECG is not made properly. Mistakes do happen and leads can be switched. Always remain careful to check this or you might come to the wrong conclusions. One of the most common mistakes is to switch the right and left arm. This will result in negative complexes in I, indicating a right axis deviation!

Common mistakes are reversal of:

  • right leg and right arm:
    • Hardly any 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

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

  • Movement
  • Electrical interference