Lead Errors

Reversal of limb leads

COMMON LEAD ERRORS

ERRORS INVOLVING THE LIMB LEADS- Misplacement of the Einthoven limb leads

-lead reversal, common (eg. Right arm- left arm reversal)

- more complex misplacements (uncommon)

- Miplacement of the ground cable (eg. Right arm – right leg cable reversal)

- ERRORS INVOLVING THE CHEST LEADS- Lead reversal (eg. V1-V3 reversal)

- Incorrect placement of a lead electrode

ERRORS INVOLVING THE LIMB LEADSMisplacement of the Einthoven limb leads

- lead reversal, common (eg. Right arm- left arm reversal)

- more complex misplacements (uncommon)

- Miplacement of the ground cable (eg. Right arm – right leg cable reversal)

Ground

64 year old man

in the Emergency Dept.See next slide for interpretation

64 year old man

In the Emergency Dept.

P wave and QRS complex are negative in lead I and positive in aVR.

Suspect lead error: left arm – right arm lead reversal

00936b

ECG recorded 1 min. later with correct lead placement

The tracing is normal

Compare the two tracings

Notice that in the incorrectly recorded tracing:a) aVR and aVL have been reversed and Lead I is “upside-down”

b) Lead II is actually lead III and lead

III is lead II

Incorrectly recorded tracing

Mr. Jerry C. 68 year old man in the CVS floor prior to bypass surgery

. Sinus rhythm. Inferior infarction, age undetermined

Mr. Jerry C. Tracing recorded on the following day in the CVS ICU .

The previous inferior infarction has suddenly “disappeared”!....

Correct lead placement

Incorrect lead placement

Notice: Left arm – left leg cable reversal

If unexpectedly an inferior infarctionappears or disappears, check whetherthe left arm and left leg electrodes might have been reversed.This lead error is frequently missed.

37 year old man complaining of mild very localized left chest pain, worse on inspiration, with the characters of “chest wall pain”

The QRS in lead II is tiny “collapsed”

The QRS pattern is the limb leads is quite unusual, in contrast with the normal pattern in the chest leads. In particular,

the QRS is tiny in lead II. The possibility of lead error (right arm-right leg lead reversal was suspected).

37 year old man complaining of mild very localized left chest pain, worse on inspiration, with the characters of “chest wall pain”

As lead error was suspected, a new ECG was recorded, with careful attention tocable placement. Obviously the previous ECG had been incorrectly recorded!

RIGHT ARM-RIGHT LEG LEAD REVERSAL(THE GROUND ELECTRODE IS PLACED ON THE RIGHT ARM,

THE RIGHT ARM ELECTRODE ON THE RIGHT LEG)

GROUND

Lead III is unchanged

Lead II measures the difference of potential between right and left legs (VERY SMALL)

LEAD IILE

AD

III

LEA

D I

Lead I is close to -III

When tracing of lead II appears “collapsed” (very small voltage),suspect that the

the placement of the right arm and right leg cables may have been reversed

Please, see the “lead errors” tutorial for an animated demonstration