ECG Artifacts

Tremor artifact

• regular P waves are QRS complexes are seen despite an abnormal irregular waveform.

Lead reversal

• RA-LA reversal
  • lead I is inverted
  • leads II and II are reversed
  • aVR and aVL are reversed
  • aVF is normal
• RA-RL reversal
  • isoelectric line in II (“isolated asystole”)
  • lead aVF and aVR are identical
  • aVL is normal
• LA-LL reversal
  • lead II is inverted
  • AvL and aVF are reversed

Precordial lead misplacement

• misplaced precordial leads alters the QRS complexes and the normal progression of P, R and T waves
• precordial lead misplacement is common
  • V1 and V2 are placed too far superiorly in about half of all cases
    • initial R wvae amplitude is reduced by 0.1 mV for each interspace. This may mimic an anterior MI.
    • V1-V2 may resemble aVR when palced too far superiorly (rSr’ pattern with T wave invserion)
  • left precordial leads are placed too far inferiorly and laterally in about a third of cases
    • affects the QRS amplitudes required for the ECG criteria of LVH