ECG LEADS

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ECG LEADS

• Chapter 3

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introduction

• The heart produces electrical currents
• The body acts as a conductor of electricity

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introduction

• An ECG is a recording of the electrical activity
  of the heart
• Different views of the heart can be recorded
  using different electrodes

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INtroduction

• Electrodes are able to measure the voltages of
  the cardiac current

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Electrodes
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Electrodes

• V1 Fourth intercostal space to the right of the
  sternum.
• V2 Fourth intercostal space to the Left of the
  sternum.
• V3 Directly between leads V2 and V4.
• V4 Fifth intercostal space at midclavicular
  line.
• V5 Level with V4 at left anterior axillary line.
• V6 Level with V5 at left midaxillary line.
  (Directly under the midpoint of the armpit)

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• Electrode placement

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• Electrode and Lead are not the same thing.

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Leads

• 12 possible leads
• Six limb (extremity) leads
• Bipolar leads I, II, and III
• Unipolar leads aVR, aVL, aVF
• Six chest (precordial) leads

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limb leads

• Electrodes
• Right arm
• Left arm
• Left leg
• Right leg (ground)

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lead i

• LA electrical voltages of the heart that are
  transmitted to the left arm
• RA electrical voltages of the heart that are
  transmitted to the right arm
• The electrocardiograph sustracts RA from LA and
  the difference appears as lead I.

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lead i

• Lead one travels horizontally.
• Its left pole (LA) is postive and its right pole
  (RA) is negative.
• Therefore, lead I LA minus RA
• Shows a positive wave when an impluses moves
  towards the left arm, negative wave when an
  impuse moves away from the left arm.

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Lead II

• Lead II points downward diagonally
• Lower pole (LL) is positive and upper pole (RA)
  is negative.
• Lead II LL minus RA

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Lead III

• Lead III points downward diagonally
• Lower pole (LL) is positive and upper pole (LA)
  is negative.
• Lead III LL minus LA

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Bipolar Leads
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Unipolar or Augmented limb leads

• Record the electrical voltages at one location
  rather than relative to the voltage at another
  electrode

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limb leads

• aVR aVL aVF 0

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Limb leads

• Bipolar leads Unipolar (or augmented) leads
• Frontal plane

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Limb leads
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chest leads

• V1 to V6
• unipolar
• horizontal plane
• front to back

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Chest Leads
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ALL 12 leads
Frontal Plane
Horizontal Plane
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Monitor leads

• 12 leads are not always necessary
• Sample of a monitor lead
• V1 (positive)
• Right shoulder (negative)
• Left shoulder (ground)

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Holter Monitors