ECG basics

Question 1

What is an ECG?

Answer 1

ECG = electrocardiogram

Shows the electrical activity of the heart

Question 2

How many seconds is 1 small box?

Answer 2

0.04

Question 3

How many seconds is 1 large box?

Answer 3

0.2

Question 4

How many large boxes make up 1 seconds?

Answer 4

5

Question 5

How many large boxes make up 1 min?

Answer 5

300

Question 6

What does a P wave show?

Answer 6

Depolarisation of the atria

Question 7

What does QRS complex show?

Answer 7

Ventricular depolarisation

Question 8

What does the T wave show?

Answer 8

Ventricular repolarisation

Question 9

What are the parameters of the PR interval?

Answer 9

Start = beginning of P wave
End = beginning of Q wave

Question 10

What does the PR interval show?

Answer 10

The length of time taken for electrical activity to move from the atria to the ventricles

i,e., the length of time between the depolarisation of the atrial and the start of ventricular depolarisation

Question 11

What are the parameters of the ST segment?

Answer 11

Beginning = end of S wave
End = beginning of T wave

Question 12

What does the ST segment show?

Answer 12

The time between ventricular depolarisation and ventricular repolarisation

Question 13

What are the parameters of the RR interval?

Answer 13

Beginning = peak of one R wave
End = peak of the next R wave

Question 14

What does the RR interval show?

Answer 14

The length of time between each ventricular depolarisation

Question 15

What are the parameters of the QT interval?

Answer 15

Beginning = start of QRS complex
End = end of T wave

Question 16

What does the QT interval show?

Answer 16

The length of time between the depolarisation and repolarisation of the ventricles

Question 17

What are the chest electrodes and where are they placed?

Answer 17

V1 - 4th intercostal space right sternal edge

V2 - 4th intercostal space left sternal edge

V3 - midway between V2 and V4

V4 - left 5th intercostal mid-clavicular line

V5 - left anterior axillary line on same plane as V4

V6 - left mid-axillary line on same plane as V4 + 5

Question 18

What are the limb leads and where are they placed?

Answer 18

Red - right arm on ulnar styloid process

Yellow - left arm on ulnar styloid process

Green - medial/lateral malleolus of left leg

Black - medial/lateral malleolus of right leg

TIP : mnemonic = Ride Your Green Bike (start from the patient’s right arm and move clockwise. Remember you need to face the patient for this to work)

Question 19

What view of the heart does V1 show?

Answer 19

Septal

Question 20

What view of the heart does V2 show?

Answer 20

Septal

Question 21

What view of the heart does V3 show?

Answer 21

Anterior

Question 22

What view of the heart does V4 show?

Answer 22

Anterior

Question 23

What view of the heart does V5 show?

Answer 23

Lateral

Question 24

What view of the heart does V6 show?

Answer 24

Lateral

Question 25

What view of the heart does Lead I show?

Answer 25

Lateral

Question 26

What view of the heart does Lead II show?

Answer 26

Inferior

Question 27

What view of the heart does Lead III show?

Answer 27

Inferior

Question 28

What view of the heart does aVR show?

Answer 28

Lateral

Question 29

What view of the heart does aVL show?

Answer 29

Lateral

Question 30

What view of the heart does aVF show?

Answer 30

Inferior

Question 31

Name all the leads that provide an inferior view of the heart

Answer 31

Lead II Lead III Lead aVF

Question 32

Name all the leads that provide a lateral view of the heart

Answer 32

V5 V6 Lead I aVL aVR

Question 33

Name all the leads that provide a septal view of the heart

Answer 33

V1 V2

Question 34

Name all the leads that provide an anterior view of the heart

Answer 34

V3 V4

Question 35

What is the cardiac axis?

Answer 35

An overview of the heart's electrical activity

Question 36

What is positive deflection?

Answer 36

Movement of electrical activity towards that lead

Question 37

What is negative deflection?

Answer 37

Movement of electrical activity away from that lead

Question 38

What is the normal cardiac axis? Which leads does this lie between?

Answer 38

-30 to 90 Between aVL to aVR

Question 39

In a normal cardiac axis where is the overall direction of electrical activity?

Answer 39

Towards leads I, II & III which all show positive deflections (the most positive deflection is in lead II) Most negative deflection in the aVR as it looks at the heart in the opposite direction

Question 40

What is a right axis deviation?

Answer 40

Depolarisation is deviated/distorted towards the right - between +90 to +180

Question 41

Name some causes of right axis deviation

Answer 41

Right ventricular hypertrophy (RVD) (most common cause) - often associated with pulmonary HTN RVD causes the deflection in lead I to be more -ve and that of lead aVF/III to be more +ve

Question 41

What is a left axis deviation?

Answer 41

Depolarisation is deviated/distorted towards the left - between -30 to -90

Question 41

Name some causes of left axis deviation

Answer 41

Conduction abnormalities

Question 42

Which artery supplies the anterior and septal areas?

Answer 42

Left anterior descending (LAD)

Question 43

Which artery supplies the inferior area?

Answer 43

RCA (in 70% of people) Left circumflex (in 30% of people)

Question 44

Which artery supplies the lateral area?

Answer 44

Left circumflex Diagonal of LAD