Electrocardiography

Question 1

Flow of cardiac depolarization

Answer 1

Sinus node > atrial muscle > AV node > His bundle > bundle branches > Purkinje network > ventricular muscle

Question 2

Where does atrial depolarization start from?

Answer 2

SA node

Question 3

Where does ventricular depolarization start?

Answer 3

AV node

Question 4

What does the amplitude on the ECG represent?

Answer 4

Voltage

Question 5

What do the P and QRS waves represent?

Answer 5

P: atrial depolarization
QRS: ventricular depolarization

Question 6

What are the bipolar limb leads?

Answer 6

I, II, III

Question 7

What are the augmented limb leads?

Answer 7

aVR, aVL, aVF

Question 8

How does the P and QRS waves appear on each lead?

Answer 8

II, III, aVF -positive
aVR, aVL -negative

Question 9

What are differentials for a tall or wide P wave?

Answer 9

Tall: P pulmonale, RA dilation
Wide: P mitrale, LA dilation

Question 10

What does a prolonged P-Q interval indicate?

Answer 10

First degree AV block

Question 11

What does a narrow QRS complex indicate?

Answer 11

Supreventricular origin
normal conduction
< 70 ms dog
< 40 ms cat

Question 12

What does a wide QRS complex indicate?

Answer 12

Supraventricular origin
Damaged purkinje system
Abnormal conduction

Question 13

What does a tall R wave indicate?

Answer 13

LV enlargement

Question 14

What does a dominant S wave show?

Answer 14

RV enlargement
“right axis shift”