Chapter 1: 12 Leads

Frontal leads

I, II, III, aVR, aVL, aVF

Lead I positive and negative electrodes

Positive: Left arm

Negative: Right arm

Lead II positive and negative electrodes

Positive: Left leg

Negative: Right arm

Lead III positive and negative electrodes

Positive: Left leg

Negative: Left arm

Lead aVF positive and negative electrodes

Positive: Left leg

Negative: Left and right arms

Lead aVL positive and negative electrodes

Positive: Left arm

Negative: Left leg and right arm

Lead aVR positive and negative electrodes

Positive: Right arm

Negative: Left leg and left arm

Lead I angle

+0º

Lead II angle

+60º

Lead III angle

+120º

Lead aVR angle

-150º

Lead aVL angle

-30º

Lead aVF angle

+90º

Which leads are unipolar?

Augmented leads (aVR, aVL, aVF)

Precordial leads measure the direction of electrical forces moving

Anteriorly and posteriorly

What is the proper placement of precordial leads?

V1 - 4th IC space, R of sternum

V2 - 4th IC space, L of sternum

V3 - between V2 and V4

V4 - 5th IC space, Mid Clavicular line

V5 - between V4 and V6 or Anterior Axillary line

V6 - 5th IC space, Mid Axillary line

Right leads

aVR and V1

Left lateral leads

I, aVL, V5, and V6

Anterior leads

V2, V3, and V4

Inferior leads

II, III, and aVF

___________ lead(s) will see P wave as purely negative deflection

aVR

____________ lead(s) will see often biphasic P wave

III and V1

___________ lead(s) will see a positive P wave

I, II, aVL, V5, and V6

For ___________ lead(s) the P wave is variable

V2, V3, and V4

A Q wave is seen in leads ___________

aVL, I, V5 and V6

V1 usually records a small ______ wave and a deep _______ wave

1. R

2. S

QRS is biphasic in lead(s) ___________

V3 and V4

Transition zone

Which leads record the biggest R wave?

V5 and V6

Which wave is susceptible to cardiac and non-cardiac influences (hormonal or neurologic)?

T wave

The T wave is negative in what lead(s)?

aVR and V1

V1 and V2 are sometimes referred to as

Septal leads

→ V3 and V4 are called Anterior leads