12-lead ECG interpretation

Question 1

Information provided by leads V1 & V2

Answer 1

• close to right ventricle
• also close to septum –> can see septal infarcts
• increased voltage from R ventricular hypertrophy seen here

Question 2

Information provided by leads V5 & V6

Answer 2

• close to left ventricle, esp. @ anterolateral portion
• anterolateral infarcts becomes visible
• increase voltage from L ventricular hypertrophy seen here

Question 3

Normal direction of depolarization of ventricles

Answer 3

• from R to L

- downward from R arm to L leg

Question 4

“Negative” leads

Answer 4

• aVR (@ R arm)

- V1 & V2

Question 5

“Positive” leads

Answer 5

-Leads I & II

Question 6

Normal QRS axis and corresponding leads

Answer 6

• QRS axis = +90deg. (straight down) to -30deg. (slightly above horizontal)
• Lead I = @ 90deg.
• Lead II = @ -30deg.

Question 7

Normal axis @ leads I and II

Answer 7

• Lead 1=positive

- Lead 2=positive

Question 8

Left axis @ leads I and II

Answer 8

• Lead 1=positive

- Lead 2=negative

Question 9

Right axis @ leads I and II

Answer 9

• Lead 1=negative

- Lead 2=positive

Question 10

Intermediate axis @ leads I and II

Answer 10

• Lead 1=negative

- Lead 2=negative

Question 11

EKG changes in Right bundle branch block

Answer 11

• wide QRS
• tall late positive deflection @ right-sided leads (V1 & V2)
• negative deflection + wide S @ left-sided leads (I & V6)

Question 12

EKG changes in Left bundle branch block

Answer 12

• wide QRS
• negative deflection @ right leads (V1)
• positive deflection @ L lead (V6)

Question 13

EKG changes in distal left bundle branch blocks

Answer 13

• distal blocks –> axis shifts
• @ anterior fascicle = L axis deviation
• @ posterior fascicle = R axis deviation
• QRS not significantly prolonged