ECG limb-lead reversal

Amuse-bouche yesterday was an ECG with limb-lead reversal. These are important to pick-up as some can mimic clinical scenarios.
Findings and clinical mimics of common limb-lead changes:
Right arm-Left arm:

• Q wave I, aVL


• Inverted p-wave I, II, II, aVF


• Mimics: old lateral infarct, non-sinus atrial activity, dextrocardia (limb lead reversal will still have normal R-wave progression, dextrocardia will not)

Right arm- Left leg:

• Q wave II, III, aVF


• Inverted p-wave II, III, aVF


• Mimics: old inferior infarct, non-sinus atrial activity

Right arm- Right leg:

• Diffuse low voltage in limb leads (esp. lead II)


• Mimics: any condition causing low voltage (limb-lead reversal will have normal precordial voltages)

Other limb lead reversals causing only minor changes with no real clinical mimics include Left arm- Left leg, Left arm- Right leg and leg-leg reversals. Precordial lead changes will interfere mostly with R-wave progression.

More from an old but concise review here.