23-53: Limb Lead Reversal

ECG Findings (dependent on which leads are reversed)

• Reversal of the left arm (LA) and right arm (RA) most common

  P, QRS, and T predominantly downgoing in lead I

  P, QRS, T upgoing in lead aVR

  Precordial leads unaffected

• Reversal of the leg leads (left leg [LL] and right leg [RL])

  Does not commonly produce ECG changes because RL is used as a grounding electrode

• Reversal of LA-LL

  Transposition of leads I and II and leads aVF and aVL with reversal of lead III

• Reversal of RA-RL

  Transposition of aVR and aVL and inversion of lead II

• Incorrect precordial lead placement

  Isolated reversal of the usual R-wave progression from V₁ to V₆

Pearls

1. If the ECG seems to have an unusual axis or appearance, especially when compared with a prior ECG on the same patient, consider a lead misplacement and repeat the tracing, confirming correct lead positions.

2. A “reversed” lead I with normal-appearing V leads strongly suggests accidental limb lead reversal as opposed to dextrocardia. Dextrocardia features a “reversed” lead I, while QRS deflections in V₄ to V₆ appear small and downgoing.