3. ECG

Question 1

What is responsible for the P wave form?

Answer 1

Atrial depolarisation

Question 2

What does the PR interval represent?

Answer 2

Delay at AV node

Question 3

How long should the PR interval last?

Answer 3

.1 second

Question 4

What does the Q wave represent?

Answer 4

Left bundle branch depolarising the intraventricular septum

Question 5

Why is the Q wave deflected negatively?

Answer 5

Moves from left heart to right heart so causes negative deflection as it moves towards negative electrode

Question 6

What does the QRS wave represent and why is it shown as positive?

Answer 6

Depolarisation of the ventricles

Left ventricle is bigger than right so mean vector is towards positive electrode

Question 7

What is the S wave?

Answer 7

Depolarisation moves upwards and around ventricles, causing a negative deflection as they move away from positive electrode

Question 8

Why is the T wave shown as a positive deflection?

Answer 8

Wave of negative charge moves towards the negative electrode so it appears positive

Question 9

Which leads show the inferior view of the heart?

Answer 9

2, 3, AVF

Question 10

Which leads show the anterior surface of the heart?

Answer 10

V1-4

Question 11

Which leads show the lateral surface of the heart?

Answer 11

1, AVL, V5, V6

Question 12

Which leads show the right atrium?

Answer 12

V1, AVR

Question 13

Which leads show the Q wave?

Answer 13

3, AVR, V1, V6

Question 14

How long is a normal P wave?

Answer 14

120-200mS

Question 15

How long is a normal QRS complex?

Answer 15

<120mS

Question 16

What is the value of 1 large box and 1 small box on the x-axis?

Answer 16

Large: .2 seconds
Small: .04 seconds

Question 17

What is the value of 1 large box and 1 small box on the y-axis?

Answer 17

Large: .5
Small: .1

Question 18

How do you calculate the HR using an ECG for a regular rhythm?

Answer 18

Count the number of boxes between 2 QRS and then divide 300 by that number

Question 19

How do you calculate the HR using an ECG for an irregular rhythm?

Answer 19

Multiply number of QRS on rhythm strip by 6

Question 20

What does no p wave mean?

Answer 20

Atrial fib

Question 21

What does a sawtooth pattern on ECG mean?

Answer 21

Atrial flutter

Question 22

Define 1st degree heart block

Answer 22

PR interval>200mS

Question 23

What can 2nd degree heart block be classified into?

Answer 23

Mobitz type 1 and 2

Question 24

Define 2nd degree mobitz type 1 heart block

Answer 24

Progressively prolonged PR until QRS is missing

Question 25

Define 2nd degree mobitz type 2 heart block

Answer 25

Prolonged PR and a new ratio of PR:QRS

Question 26

Define 3rd degree heart block

Answer 26

No relation between p and QRS

Question 27

What is the axis of an ECG?

Answer 27

Average direction of flow of electricity through the heart

Question 28

What is a normal axis?

Answer 28

90 to -30 degrees

Question 29

What range is a left axis deviation?

Answer 29

-30 to -90

Question 30

What range is a right axis deviation?

Answer 30

90 to 180

Question 31

Describe how to find the axis on an ECG

Answer 31

Find the lead with the smallest deflections Find the lead perpendicular to this lead; is it mostly positive or negative? Where is this lead positive/negative?

Question 32

How is bundle branch block seen on an ECG?

Answer 32

QRS >120mS, due to slow depolarisation through blocked branches

Question 33

How can a right BBB be seen on an ECG?

Answer 33

QRS>120 M-shaped QRS in V1 Prominent S wave in 1 and aVL

Question 34

What are the causes of right BBB?

Answer 34

Lung disease PE Atrial septal defect

Question 35

How can a left BBB be seen on an ECG?

Answer 35

QRS >120 Broad R wave in 1, aVL, V6 ST depression leading into an inverted T wave

Question 36

What are the causes of left BBB?

Answer 36

STEMI Aortic stenosis Cardiomyopathy

Question 37

What are the causes of an elevated ST segment?

Answer 37

Acute transmural infarction Pericarditis Aneurysm Brugada syndrome

Question 38

What are the causes of a depressed ST segment?

Answer 38

NSTEMI Digoxin Hypo K+, Ca++, Mg++

Question 39

What are the causes of a peaked T wave?

Answer 39

Hyperacute infaction | Hyper K+, Ca++, Mg++

Question 40

What are the causes of an inverted T wave?

Answer 40

Infarction Ischaemia Hypo K+, Ca++, Mg++

Question 41

What 2 indexes are used to determine the hypertrophy voltage criteria?

Answer 41

Sokolow-Lyon index | Cornell

Question 42

What is the Sokolow-Lyon index?

Answer 42

S in V1 + R in V5/6 > 7 big squares

Question 43

What is the Cornell index?

Answer 43

S in V3 + R in aVL >28mm (men) >20 (women)

Question 44

What are the causes of hypertrophy?

Answer 44

Hypertension Ischaemic heart disease Cardiomyopathy Aortic stenosis