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ECG Lead Misplacement

ECG lead misplacement

Limb Electrodes

Correct limb electrodes position, left arm (LA), right arm (RA), right leg - neutral, left leg
  • Limb electrodes are clipped onto the limbs
    • onto the wrists and ankles
    • Height placement does not matter
  • Electrode placement
    • Red - right arm (RA)
    • Yellow - left arm (LA)
    • Green - left leg (LL)
    • Black - right leg (RL)
  • With 3 limb electrodes
    • The ECG machine generates 6 ECG leads on paper:
      • Limb leads (I, II, III, aVL, aVF, aVR)

Limb Leads

Einthoven triangle, Wilson central terminal - electrical center of heart, limb leads and electrodes

Main Electrical Vector

Electrical QRS axis in frontal plane with limb leads
  • When you shift the ECG leads to the central terminal
  • Each lead "views" the vector from a different angle
  • The direction of the vector determines the height of the QRS complex (in that lead)

  • For diagnosing incorrectly placed limb electrodes
    • You need to visualize the direction of the main vector
      • The QRS is positive if the vector is TOWARD the leads
      • The QRS is negative if the vector is AWAY FROM the leads

Einthoven's Triangle

Relation between the limb leads and electrodes in Einthoven triangle

Pseudo-Asystole and Neutral Electrode

  • Switched limb electrodes that form the Einthoven triangle
    • Change the leads on the EKG paper
  • However, if you connect a neutral electrode (on the left leg) into the triangle
    • A pseudo-asystole will appear in one of the Einthoven leads

ECG pseudo-asystole in lead III, LA/RL (left arm, right arm) reversal electrodes

Pseudo-Asystole III

  • Switched (LA/RL)

ECG pseudo-asystole in lead II, RA/RL (right arm, right leg) reversal electrodes

Pseudo-Asystole II

  • Switched (RA/RL)

ECG pseudo-asystole in lead I, RA/RL (right arm, right leg) and LA/LL (left arm, left leg) reversal electrodes

Pseudo-Asystole I

  • Switched (RA/RL) and (LA/LL)

Left Arm/Right Arm (LA/RA)

Reversal ECG LA and RA (left arm, right arm) electrodes position in Einthoven triangle

ECG paper with correct RA LA (right arm, left arm) limb electrodes

Correctly Positioned Electrodes


ECG paper with reversed RA LA (right arm, left arm) limb electrodes

Reversed: Left Arm/Right Arm

  • Lead I is inverted
  • Leads aVL and aVR are swapped
  • Leads II and III are swapped
  • aVF remains unchanged

Left Arm/Left Leg (LA/LL)

Reversal of LA and LL (left arm, left leg) limb electrodes position in Einthoven's triangle

ECG paper with correct LA LL (left arm, left leg) limb electrodes

Correctly Placed Electrodes


ECG paper with reversal LA LL (left arm, left leg) limb electrodes

Reversed: Left Arm/Left Leg

  • Lead III is inverted
  • Leads I and II are swapped
  • Leads aVL and aVF are swapped
  • aVR remains unchanged

Right Arm/Left Leg (RA/LL)

Reversal RA and LL (right arm, left leg) limb electrodes position in Einthoven triangle

ECG paper with correct RA LL (right arm, left leg) limb electrodes

Correctly Placed Electrodes


ECG paper with reversal RA LL (right arm, left leg) limb electrodes

Reversed: Right Arm/Left Leg

  • Lead II is inverted
  • Leads aVF and aVF are swapped
  • Leads I and III are inverted and swapped
  • aVL remains unchanged

Right Arm/Right Leg (RA/RL)

Reversal RA and RL (right arm, right leg) limb electrodes position and collapses Einthoven triangle

ECG paper with correct RA RL (right arm, right leg) limb electrodes

Correctly Placed Electrodes

ECG paper with reversal RA RL (right arm, right leg) limb electrodes, pseudo-asystole II

Reversed: Left Arm/Right Arm

  • Pseudo-asystole in Lead II
  • Lead I is the inverted Lead III
  • Lead II is isoelectric (because it has disappeared)
  • Lead III is unchanged
  • aVL is the inverted Lead III
  • aVR = aVF

Left Arm/Right Leg (LA/RL)

Reversal LA and RL (left arm, right leg) limb electrodes position and collapses Einthoven triangle

ECG paper with correct LA RL (left arm, right leg) limb electrodes

Correctly Placed Electrodes


ECG paper with reversal LA RL (left arm, right leg) limb electrodes, pseudo-asystole III

Reversed: Left Arm/Right Leg

  • Pseudo-asystole in Lead III
  • Leads I and II are identical
  • Lead II is unchanged
  • Lead III is isoelectric (because it has disappeared)
  • aVR is the inverted Lead II
  • aVL = aVF

Right Arm/Right Leg + Left Arm/Left Leg
(RA/RL) + (LA/LL)

Bilateral reversal of transposition electrodes in Einthoven's triangle

ECG paper with correctly placed limb electrodes

Correctly Placed Electrodes


ECG paper with bilateral reversal electrodes, pseudo-asystole I

Reversed: Left Arm/Right Arm

  • Pseudo-asystole in Lead I
    • Lead I is isoelectric (because it has disappeared)
  • Leads II, III, and aVF are identical
    • Lead III is inverted
    • Lead II is the inverted Lead III
    • aVF is the inverted Lead III
  • aVR = aVL

Left Leg/Right Leg (LL/RL)

Reversal LL and RL limb electrodes position

ECG paper with correct position of limb electrodes

Correctly Placed Electrodes


Unchanged ECG paper after reversal of LL and RL electrodes

Reversed: Left Arm/Right Arm

  • ECG Leads are Unchanged



Sources

  • ECG from Basics to Essentials Step by Step
  • litfl.com
  • ecgwaves.com
  • metealpaslan.com
  • medmastery.com
  • uptodate.com
  • ecgpedia.org
  • wikipedia.org
  • Strong Medicine
  • Understanding Pacemakers





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Home /

ECG Lead Misplacement

ECG lead misplacement

Limb Electrodes

  • Limb electrodes are clipped onto the limbs
    • onto the wrists and ankles
    • Height placement does not matter
  • Electrode placement
    • Red - right arm (RA)
    • Yellow - left arm (LA)
    • Green - left leg (LL)
    • Black - right leg (RL)
  • With 3 limb electrodes
    • The ECG machine generates 6 ECG leads on paper:
      • Limb leads (I, II, III, aVL, aVF, aVR)
Correct limb electrodes position, left arm (LA), right arm (RA), right leg - neutral, left leg

Limb Leads

  • Limb electrodes are attached to the body
    • The ECG machine generates ECG leads on paper from the electrodes
  • The ECG machine generates the following from the limb electrodes:
Einthoven triangle, Wilson central terminal - electrical center of heart, limb leads and electrodes

Main Electrical Vector

  • When you shift the ECG leads to the central terminal
  • Each lead "views" the vector from a different angle
  • The direction of the vector determines the height of the QRS complex (in that lead)

  • For diagnosing incorrectly placed limb electrodes
    • You need to visualize the direction of the main vector
      • The QRS is positive if the vector is TOWARD the leads
      • The QRS is negative if the vector is AWAY FROM the leads
Electrical QRS axis in frontal plane with limb leads

Einthoven's Triangle

  • When you swap the limb electrodes
    • Except for the black electrode (ground)
    • You rotate the Einthoven's triangle by 180°
      • The corresponding ECG leads will be mirrored
  • If you swap the leg electrodes (green with black)
    • No impact on ECG leads
      • Because it does not affect the Einthoven's triangle
  • If you swap the black electrode with an arm electrode
 Relation between the limb leads and electrodes in Einthoven triangle

Pseudo-Asystole and Neutral Electrode

  • Switched limb electrodes that form the Einthoven triangle
    • Change the leads on the EKG paper
  • However, if you connect a neutral electrode (on the left leg) into the triangle
    • A pseudo-asystole will appear in one of the Einthoven leads

ECG pseudo-asystole in lead III, LA/RL (left arm, right arm) reversal electrodes

Pseudo-Asystole III

  • Switched (LA/RL)
 ECG pseudo-asystole in lead II, RA/RL (right arm, right leg) reversal electrodes

Pseudo-Asystole II

  • Switched (RA/RL)
 ECG pseudo-asystole in lead I, RA/RL (right arm, right leg) and LA/LL (left arm, left leg) reversal electrodes

Pseudo-Asystole I

  • Switched (RA/RL) and (LA/LL)

Left Arm/Right Arm (LA/RA)

  • The Einthoven triangle rotates 180°
  • ECG Changes
    • Lead I is inverted
    • Leads aVL and aVR are swapped
    • Leads II and III are swapped
    • aVF remains unchanged

  • Dextrocardia
Reversal ECG LA and RA (left arm, right arm) electrodes position in Einthoven triangle


ECG paper with correct RA LA (right arm, left arm) limb electrodes ECG paper with reversed RA LA (right arm, left arm) limb electrodes

Correctly Positioned Electrodes

Reversed: Left Arm/Right Arm

  • Lead I is inverted
  • Leads aVL and aVR are swapped
  • Leads II and III are swapped
  • aVF remains unchanged

Left Arm/Left Leg (LA/LL)

  • Einthoven's triangle rotates 180°
  • ECG Changes
    • Lead III is inverted
    • Leads I and II are swapped
    • Leads aVL and aVF are swapped
    • aVR remains unchanged
Reversal of LA and LL (left arm, left leg) limb electrodes position in Einthoven's triangle


ECG paper with correct LA LL (left arm, left leg) limb electrodes ECG paper with reversal LA LL (left arm, left leg) limb electrodes

Correctly Placed Electrodes

Reversed: Left Arm/Left Leg

  • Lead III is inverted
  • Leads I and II are swapped
  • Leads aVL and aVF are swapped
  • aVR remains unchanged

Right Arm/Left Leg (RA/LL)

  • Einthoven's Triangle rotates 180°
  • ECG Changes
    • Lead II is inverted
    • Leads aVR and aVF are swapped
    • Leads I and III are inverted and swapped
    • aVL remains unchanged
Reversal RA and LL (right arm, left leg) limb electrodes position in Einthoven triangle


ECG paper with correct RA LL (right arm, left leg) limb electrodes ECG paper with reversal RA LL (right arm, left leg) limb electrodes

Correctly Placed Electrodes

Reversed: Right Arm/Left Leg

  • Lead II is inverted
  • Leads aVF and aVF are swapped
  • Leads I and III are inverted and swapped
  • aVL remains unchanged

Right Arm/Right Leg (RA/RL)

  • The black (neutral) electrode (ground) is on the right leg
    • It is not part of the Einthoven triangle
  • The Einthoven triangle becomes distorted:
    • Lead II disappears
    • Wilson's Central Terminal has shifted
    • Electrodes on the legs measure identical voltages (aVR = aVF)
    • aVL lead is oriented opposite to lead III

  • EKG Changes
    • Pseudo-asystole in Lead II
    • Lead I is the inverted Lead III
    • Lead II is isoelectric (because it has disappeared)
    • Lead III is unchanged
    • aVL is the inverted Lead III
    • aVR = aVF
    • Wilson's Central Terminal has shifted
      • The precordial leads (V1-V6) are also distorted
Reversal RA and RL (right arm, right leg) limb electrodes position and collapses Einthoven triangle


ECG paper with correct RA RL (right arm, right leg) limb electrodes ECG paper with reversal RA RL (right arm, right leg) limb electrodes, pseudo-asystole II

Correctly Placed Electrodes

Reversed: Left Arm/Right Arm

  • Pseudo-asystole in Lead II
  • Lead I is the inverted Lead III
  • Lead II is isoelectric (because it has disappeared)
  • Lead III is unchanged
  • aVL is the inverted Lead III
  • aVR = aVF

Left Arm/Right Leg (LA/RL)

  • The black electrode is placed on the right leg (grounding)
    • It is not part of the Einthoven triangle
  • The Einthoven Triangle is distorted:
    • Lead III disappears
    • The Wilson Central Terminal has shifted
      • Precordial leads (V1-V6) are also distorted
    • Leads aVL and aVF record identical voltages (aVL = aVF)
    • Lead aVR is directed opposite to Lead II

  • ECG Changes
    • Pseudo-asystole in Lead III
    • Leads I and II are identical
    • Lead II is unchanged
    • Lead III is isoelectric (because it has disappeared)
    • aVR is the inverted Lead II
    • aVL = aVF
    • The Wilson Central Terminal has shifted
      • Precordial leads (V1-V6) are also distorted
Reversal LA and RL (left arm, right leg) limb electrodes position and collapses Einthoven triangle


ECG paper with correct LA RL (left arm, right leg) limb electrodes ECG paper with reversal LA RL (left arm, right leg) limb electrodes, pseudo-asystole III

Correctly Placed Electrodes

Reversed: Left Arm/Right Leg

  • Pseudo-asystole in Lead III
  • Leads I and II are identical
  • Lead II is unchanged
  • Lead III is isoelectric (because it has disappeared)
  • aVR is the inverted Lead II
  • aVL = aVF

Right Arm/Right Leg + Left Arm/Left Leg
(RA/RL) + (LA/LL)

  • This is a bilateral electrode reversal
    • Both arm electrodes are on the legs
  • Einthoven's triangle is distorted:
    • Lead I disappears
    • Wilson's Central Terminal has shifted
      • Precordial leads (V1-V6) are also distorted
    • Leads aVR and aVL record identical voltages (aVR = aVL)
    • Leads II, III, and aVF are identical

  • EKG Changes
    • Pseudo-asystole in Lead I
    • Lead I is isoelectric (because it has disappeared)
    • Leads II, III, and aVF are identical
      • Lead III is inverted
      • Lead II is the inverted Lead III
      • aVF is the inverted Lead III
    • aVR = aVL
    • Wilson's Central Terminal has shifted
      • Precordial leads (V1-V6) are also distorted
Bilateral reversal of transposition electrodes in Einthoven's triangle


ECG paper with correctly placed limb electrodes ECG paper with bilateral reversal electrodes, pseudo-asystole I

Correctly Placed Electrodes

Reversed: Left Arm/Right Arm

  • Pseudo-asystole in Lead I
    • Lead I is isoelectric (because it has disappeared)
  • Leads II, III, and aVF are identical
    • Lead III is inverted
    • Lead II is the inverted Lead III
    • aVF is the inverted Lead III
  • aVR = aVL

Left Leg/Right Leg (LL/RL)

  • Einthoven's Triangle remains unchanged
    • The bottom angle moves to the right leg

  • ECG leads are unchanged
Reversal LL and RL limb electrodes position


ECG paper with correct position of limb electrodes Unchanged ECG paper after reversal of LL and RL electrodes

Correctly Placed Electrodes

Reversed: Left Arm/Right Arm

  • ECG Leads are Unchanged



Sources

  • ECG from Basics to Essentials Step by Step
  • litfl.com
  • ecgwaves.com
  • metealpaslan.com
  • medmastery.com
  • uptodate.com
  • ecgpedia.org
  • wikipedia.org
  • Strong Medicine
  • Understanding Pacemakers