ECG placement & mis-LEADing ECG’s

  • V1: 4th intercostal space (ICS), RIGHT margin of the sternum
  • V2: 4th ICS along the LEFT margin of the sternum
  • V4: 5th ICS, mid-clavicular line
  • V3: midway between V2 and V4
  • V5: 5th ICS, anterior axillary line (same level as V4)
  • V7: Left posterior axillary line, in the same horizontal plane as V6.
  • V8: Tip of the left scapula, in the same horizontal plane as V6.
  • V9: Left paraspinal region, in the same horizontal plane as V6.

Why is placement important?

We had nurses place the chest lead on to a single relatively healthy subject in common configurations they had used, with ECG-4  an example of placement used if large breasts were encountered (the limb leads and ECG machine did not varied through this, nor did the victims health).

As you can see morphology changed significantly with position, highlighting the need to consistency of placement especially when repeating ECG’s on an individual you are observing for subtle S-T or T-wave changes. As misplacement could artificially improve or worsen the ECG.

  • Comparing ECG-1 and ECG-4 you can see T-inversion develop inferiorly and V2+2.
    • Lead V1 and V2 there are P and T wave inversion (signalling misplacement) – [too high]
      • Leads II-III there is no P inversion, although R wave progression from lead I-II appears abnormal.
    • Leads II-III appear to have slight ST-depression
    • Leads II-III & V6 also has the what may be mistaken for a Q-wave

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