Changes in the Electrocardiogram Associated with Lead Misplacement

Misplacement of ECG leads can cause artifacts in the electrocardiogram.

ECG Finding	Lead Misplacement
old lateral MI	reversal RA and LA
old inferior MI	reversal RA and LL
posterolateral MI	reversal of precordial leads
anterior MI	precordial leads to high on chest
right bundle-branch block (rSR' complex)	precordial leads to high on chest
non-sinus atrial rhythm	reversal RA and LA; reversal RA and LL; reversal of RA and RL
diffuse low voltage	reversal of RA and RL
mirror-image dextrocardia	reversal of precordial leads
inverted P waves in I, II, III, aVL	reversal RA and LA
large q-wave in I, aVL	reversal RA and LA
I and aVL as inversions of V5 and V6	reversal RA and LA
inverted P waves in II, III, aVF	reversal RA and LL
large q wave in II, III, aVF	reversal RA and LL
insignificant q wave in III	reversal of LA and LL
low voltage in III	reversal of LA and RL
junctional rhythm	reversal of RA and RL

where:

• RA = right arm; RL = right leg; LA = left arm; LL = left leg

• Reversal of RL and LL leads is not associated with a change in the ECG.

• The right leg (RL) lead is ground.

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