Electocardiogram(ECG or EKG) is a noninvasive test that is used to reflect underlying heart conditions by measuring the electrical activity of the heart. ECG or EKG leads are attached attached to each extremity (4 total) and to 6 precordial leads on the front of the chest.

Important components of ECG and their representations:



  1. P wave: Depolarization of the right and left atria
  2. QRS complex: Right and left ventricular depolarization
  3. T wave: Ventricular repolarization
  4. U wave: Late repolarization of papillary muscles
  5. PR interval: time interval from onset of atrial depolarization (P wave) to onset of ventricular depolarization (QRS complex)
  6. QT interval: duration of ventricular depolarization and repolarization

Leads of ECG:

RA represents right arm
LA represents left arm
LF represents left foot

Bipolar limb leads (frontal plane):
Lead I: RA (-) to LA (+) (Right Left, or lateral)
Lead II: RA (-) to LF (+) (Superior Inferior)
Lead III: LA (-) to LF (+) (Superior Inferior)

Augmented unipolar limb leads (frontal plane):
Lead aVR: RA (+) to [LA & LF] (-) (Rightward)
Lead aVL: LA (+) to [RA & LF] (-) (Leftward)
Lead aVF: LF (+) to [RA & LA] (-) (Inferior)

Unipolar (+) chest leads (horizontal plane):
Leads V1, V2, V3: (Posterior Anterior)
Leads V4, V5, V6:(Right Left, or lateral)


12 Lead ECG Placement


Limb lead placement:
RA: Right forearm or wrist
LA: Leaft forearm or wrist
LL: Left lower leg
RL: Ground lead is generally placed on the right lower leg

Precordial Leads (V1-V6):
V1: 4th intercostal space, right sternal border
V2: 4th intercostal space, left sternal border
V3: midpoint of V2 and V4
V4: 5th intercostal space, left midclavicular line
V5: 5th intercostal space, left anterior axillary line
V6: 5th intercostal space, left mid-axillary line

Contiguous Leads:


Two leads that look at neighbouring anatomical areas of the heart are said to be contiguous.

  1. V1-V2: Septal Leads
  2. V3-V4: Anterior Leads
  3. II, III, aVF: Inferior leads
  4. V5, V6, I, aVL: Lateral leads

Learn more about ECG @ ECG Library

12 Lead ECG Placement Video

  • Uploaded by: Sulav Shrestha
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    2 comments:

    1. awesome!!! thank you

      ReplyDelete
    2. AVR is not UNIMPORTANT!!! AVR elevation in the presence of ST depression in other leads indicates left main coronary aertery disease!

      ReplyDelete

     

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