12 Lead Basics

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12 Lead Basics
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Objectives

• Coronary Artery Anatomy
• What the Leads See
• Lead Placement
• Skin Preparation

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Coronary Artery Anatomy

• The 12 lead shows which area of the heart is
  ischemic or damaged
• This corresponds to the artery that is occluded

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Coronary Artery Anatomy

• Right Coronary Artery
• Supplies
• Right ventricle, inferior and posterior wall
• SA and AV node

Right Coronary Artery
Right Ventricle
Inferior Wall
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Coronary Artery Anatomy

• Left Main Coronary Artery
• Left Anterior Descending and Circumflex arteries
  branch off the Left Main
• Occlusion of the left main has very poor prognosis

Left Main Coronary Artery
Left Anterior Descending
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Coronary Artery Anatomy

• Left Anterior Descending
• Supplies
• Anterior and Septal wall of the left ventricle

Left Anterior Descending
Anteroseptal
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Coronary Artery Anatomy
Posterior view of heart and arteries

• Left Circumflex Artery
• Supplies
• Posterior wall
• Lateral wall
• Inferior wall in 10 of the population

Posterior wall
Lateral wall
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Normal 12 Lead

• This an example of a 12 lead that the Zoll E
  series will generate
• The 12 lead only provides a view of the left
  ventricle, the right ventricle and posterior wall
  is not seen with a 12 lead
• To view the right ventricle or posterior wall a
  15 lead ECG would need to be done we are not
  covering this or doing this in the field at this
  time

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12 Lead ECG

• Limb Leads (I, II, III, aVR, aVL, aVF)
• 3 bipolar leads (I, II, III)
• 3 unipolar leads (aVR, aVL, aVF)
• Place electrodes on the limbs if there is a 12
  lead in the patients future highly preferable
  to torso placement

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12 Lead ECG

• Chest Leads (V1, V2, V3, V4, V5, V6)
• 6 unipolar electrodes
• Electrodes are placed on the chest
• Preparing the skin improves tracing (more about
  that later)

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Limb Lead Placement

• Place leads on limbs
• Away from major muscles or arteries
• Have patient remain still during 12 lead
  acquisition (to reduce artifact)

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Chest Lead Placement

• V1 is placed in the 4th intercostal space to the
  right of the sternal boarder
• To find the 4th intercostal space feel for the
  clavicle
• Just below the clavicle is the 2nd rib, then the
  3rd and 4th rib
• Between the 4th rib and the 5th rib is the 4th
  intercostal space
• V2 is placed to the left of the sternal boarder
  in the 4th intercostal space

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Chest Lead Placement

• V4 is placed next in the 5th intercostal space in
  the mid-clavicular line
• Find the half way mark on the left clavicle and
  move down one rib so V4 is between the 5th and
  6th ribs
• V3 is placed after V4 and is simply placed in
  between V2 and V4 either on the 5th rib or in the
  5th intercostal space

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Chest Lead Placement

• V5 is placed in the 5th intercostal space and the
  anterior axillary line
• To find the anterior axillary line lay the
  patients left arm at their side and follow the
  crease line in their armpit down the front of
  their chest
• V6 is placed in the 5th intercostal space in the
  mid-axillary line

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Chest Lead Placement
V1 4th intercostal space to the right of the
sternum
V2 4th intercostal space to the left of the
sternum
V3 directly between V2 and V4
V4 5th intercostal space at the left
mid-clavicular line
V5 level with V4 at the anterior axillary line
V6 level with V5 at the mid-axillary line
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Skin Prep

• Dry moist skin
• Clip or shave excess hair
• Abrade dead skin with skin prep tape or dry 4x4
  gauze
• These measures improve the 12 lead tracing

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Inferior Wall

• II, III, aVF
• View from Left Leg ?
• inferior wall of left ventricle

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Inferior Wall

• Posterior View
• portion resting on diaphragm
• ST elevation in leads II, III, aVF suspect
  inferior injury

Inferior Wall
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Lateral Wall

• I and aVL
• View from Left Arm ?
• lateral wall of left ventricle

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Lateral Wall

• V5 and V6
• Left lateral chest
• lateral wall of left ventricle

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Lateral Wall

• I, aVL, V5, V6
• ST elevation suspect lateral wall injury

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Anterior Wall

• V3, V4
• Left anterior chest
• ? electrode on anterior chest

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Anterior Wall

• V3, V4
• ST segment elevation suspect anterior wall
  injury

Anterior Wall
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Septal Wall

• V1, V2
• Along sternal borders
• Look through right ventricle see septal wall

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Septal

• V1, V2
• ST segment elevation suspect septal wall injury
• septum is left ventricular tissue

Septal Wall
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Remember to SAIL through it!

• Septal leads V1 and V2
• Anterior leads V3 and V4
• Inferior leads II, III, aVF
• Lateral leads I, aVL, V5 and V6

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What about aVR?

• aVR does not face the epicardial surface so it
  does not provide information regarding ischemia
• aVR is therefore not used for identification of
  STEMI

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