Basic ECG (Reading)

Question 1

Why is it necessary to do multiple ECGs?

Answer 1

Takes only one picture in time

Need to do multiple to compare

Question 2

What other lead ECGs can be done?

Answer 2

3 and 5

Question 3

What is the baseline?

Answer 3

Isoelectric line

Question 4

What is the ECG paper speed?

Answer 4

25 mm/sec

Question 5

What is the paper square size?

Answer 5

Small square = 0.04 sec
Large square = 0.2 sec
Small square = 0.1 mV
2 large squares = 1 mV

Question 6

What is happening in the heart if the line is flat at any time in the ECG?

Answer 6

No electrical activity at that particular moment

Question 7

What does the direction in which the waves point indicate?

Answer 7

Whether electricity is moving towards or away from a particular lead

Question 8

What are the six chest leads and where are they attached?

Answer 8

V1, V2, V3, V4, V5, V6

Attached across patients chest

Question 9

What are the three limb leads and where are they attached?

Answer 9

aVR = right arm
aVL = left arm
aVF = left leg

Question 10

What is the lead that is attached to the right leg?

Answer 10

Earth, not active lead

Question 11

What are the three bipolar leads?

Answer 11

Lead I, lead II, lead III

Question 12

What is Einthoven’s Triangle?

Answer 12

Triangle, or line of sight created by the three limb leads
These form leads I, II, and III
Leads run negative to positive

Question 13

What forms lead I?

Answer 13

aVR (-) to aVL (+)

Question 14

What forms lead II?

Answer 14

aVR (-) to aVF (+)

Question 15

What forms lead III?

Answer 15

aVL (-) to aVF (+)

Question 16

What is the universal monitoring lead?

Answer 16

Lead II

Question 17

How do you measure the rate with a regular rhythm?

Answer 17

Number of large squares between 2 R waves/300

Question 18

How do you measure the rate with an irregular rhythm?

Answer 18

Number of QRS complexes in 6 second strip x10 OR

Number of QRS complexes on an ECG page x6

Question 19

What does the P wave represent?

Answer 19

Atrial depolarisation

SA node firing

Question 20

What is the intrinsic rate of the SA node?

Answer 20

60-100 bpm

Question 21

What should the P wave be?

Answer 21

Rounded and upright in all leads, except aVR
Less than 0.12 sec (3 small squares)
1:1 with QRS complex

Question 22

What does a peaked P wave mean?

Answer 22

Right atrial enlargement

Question 23

What does a bifid or prolonged P wave mean?

Answer 23

Left atrial enlargement

Question 24

What does the PR interval represent?

Answer 24

SA node to AV node

Question 25

What should the PR interval be?

Answer 25

0.12-0.20 sec (3-5 small squares)

Question 26

What is the intrinsic rate of the AV node?

Answer 26

40-60 bpm

Question 27

What does a shortened PR interval mean?

Answer 27

Pre-excitation or alternate accessory pathway exists

Question 28

What does a prolonged PR interval mean?

Answer 28

AV block

Question 29

What does the Q wave represent?

Answer 29

First negative deflection | Depolarisation of bundle of His (septum)

Question 30

When is the Q wave abnormal and pathological?

Answer 30

If >2 mm in depth or >1/3 of R wave height

Question 31

What does an abnormal Q wave indicate?

Answer 31

Previous myocardial infarct

Question 32

What does the QRS complex represent?

Answer 32

Ventricular depolarisation

Question 33

What should the duration of the QRS complex be?

Answer 33

Less than <0.12 sec (3 small squares)

Question 34

What does a prolonged QRS complex mean?

Answer 34

Conduction delay or if impulse generated in ventricles

Question 35

What can vary the QT interval?

Answer 35

Gender Time of day Heart rate

Question 36

What is the normal QT interval?

Answer 36

Less than 0.44 sec (11 small squares) | Less than half of RR interval

Question 37

What does a prolonged QT interval indicate?

Answer 37

Delayed repolarisation due to many causes: - Congenital - Low electrolyte levels - Drugs; eg: tricyclic antidepressants

Question 38

How does the R wave change from V1 to V6?

Answer 38

Becomes more upright | V3 often biphasic

Question 39

What should the ST segment be?

Answer 39

Isoelectric

Question 40

What change in the ST segment is indicative of a myocardial infarction?

Answer 40

ST elevation >2 mm in chest leads or >1 mm in limb leads

Question 41

What can an ST depression indicate?

Answer 41

Ischaemia | Reciprocal changes

Question 42

What does the T wave represent?

Answer 42

Depolarisation of ventricles

Question 43

What should the T wave look like?

Answer 43

Upright Rounded Larger than P wave

Question 44

What can a T wave inversion indicate?

Answer 44

Myocardial ischaemia

Question 45

What does a peaked T wave indicate?

Answer 45

Hyperkalaemia

Question 46

When is the U wave most obvious?

Answer 46

Hypokalaemia

Question 47

Which leads represent the lateral surface of the heart?

Answer 47

Low lateral = V5, V6 | High lateral = I, aVL

Question 48

Which leads represent the anterior surface of the heart?

Answer 48

V3, V4

Question 49

Which leads represent the septal surface of the heart?

Answer 49

V1, V2

Question 50

Which leads represent the inferior surface of the heart?

Answer 50

II, III, aVF

Question 51

What does the S wave represent?

Answer 51

Second negative deflection | Depolarisation of Purkinje fibres

Question 52

How do you determine the rhythm?

Answer 52

Is there a P wave? Where is the rhythm being generated? Map out R - R regularity

Question 53

What indicates left atrial enlargement?

Answer 53

Bifid P wave | Terminal negative P wave deflection >1 mm deep and 0.04 (1 small square) long in V1

Question 54

What indicates right atrial enlargement?

Answer 54

Peaked P waves in V1 and V2 >1.5 mm tall

Question 55

What indicates left ventricular hypertrophy?

Answer 55

Add largest R wave of V5 or V6 to largest S wave of V1 or V2 Total >35 mm (7 large boxes) R wave in aVL >9mm in females or >11 mm in males

Question 56

What indicates right ventricular hypertrophy?

Answer 56

R wave in V1 >7 mm | S wave in V5 or V6 >7 mm

Question 57

What indicates ischaemia or infarction?

Answer 57

In contiguous leads - ST segment changes - T wave inversion - Pathological Q waves