ECG

Question 1

What is Ohm’s law

Answer 1

Voltage= current X resistance

Question 2

On as ECG what does a positive deflection show

Answer 2

The net current is travelling towards the lead

Question 3

What does it mean if there is an isoelectric point on an ECG

Answer 3

The line would be flat showing no net current in direction of a lead

Question 4

What does it mean if there is a negative deflection on an ECG

Answer 4

The next current flow is travelling away from the lead

Question 5

What is an ECG

Answer 5

Electrocardiogram

Question 6

What is an ECG used for

Answer 6

The record the electrical activity of the heart from different angles to identify and locate pathology via placing electrodes on the limps and chest of the patient

Question 7

What does the P wave represent on a healthy individuals ECG

Answer 7

Atrial depolarisation

Question 8

What does the PR interval represent in an ECG of a healthy individual

Answer 8

This interval begins at the beginning of the P wave and ends at the beginning of the Q wave and it represents the time taken for the electrical activity to move between the atria and the ventricles

Question 9

What is the QRS complex

Answer 9

The ORS Complex is 3 closely related waves that show the depolarisation of the ventricles

Question 10

What is the ST segment on the ECG

Answer 10

This segment start at the S wave and ends at the end of the T wave.
This is shown as an isoelectric line between the depolarisation and the re polarisation of the ventricles in the heart

Question 11

What is the T wave on an ECG

Answer 11

The T wave show ventricular repolarisation and is shown as a small wave after the QRS complex

Question 12

What is the QT interval on an ECG

Answer 12

This is begins at the beginning of the QRS complex and finishes at the T wave
This interval shows the depolarisation of the ventricles and then them repolarising

Question 13

What is an ECG electrode

Answer 13

It is a conductive pad that attaches to the skin that records the electrical activity of the heart

Question 14

What is an ECG lead

Answer 14

This is a lead that gives a graphical representation of the Hearts electrical activity which is calculated by data from several ECG electrodes

Question 15

How many chest electrodes are there

Answer 15

6

Question 16

What is the location of each chest electrodes on the chest wall

Answer 16

V1 is located on the 4th intercostal space at the right side of the sternal angle
V2 is located on the 4th intercostal space at the left side of the sternal angle
V3 is located midway between chest lead v2 and v4
V4 is located in the 5th intercostal space in the midclavicular line
V5 is located in the left anterior axillary line at the same horizontal level as v4
V6 is located in the left mid axillary line at the same horizontal level of v4 and v5

Question 17

How many limb leads are there

Answer 17

4

Question 18

Where are the limb leads located

Answer 18

Red lead is located on the right arm on the ulnar styloid process of the right arm
Yellow lead is located on the left arm on the ulnar styloid process of the left arm
Green lead is located on the left leg on the medial/lateral malleolus of the left leg
Black lead is located on the right leg on the medial/lateral malleolus of the right leg

Question 19

What do each chest lead show

Answer 19

V1 shows a septal view of the heart
V2 shows a septal view of the heart
V3 shows a anterior view of the heart
V4 shows a anterior view of the heart
V5 shows a lateral view of the heart
V6 shows a lateral view of the heart

Question 20

What does lead I show and how is it calculated

Answer 20

Lead I shows an inferior view of the heart and is calculated by analysing the right arm and left leg

Question 21

What does lead II show and how is it calculated

Answer 21

Lead II shows an inferior view of the heart and is calculated by analysing the right arm and left leg electrode

Question 22

What does lead III show and how is it calculated

Answer 22

Lead III shows an inferior view of the heart and is calculated by analysing the Left arm and left leg electrodes

Question 23

What does the aVR lead show and how is it calculated

Answer 23

This lead shows a lateral view and is calculated by analysing the activity between Left arm and left leg compared with right arm

Question 24

What does the aVL lead show and how is it calculated

Answer 24

This shows a lateral view of the heart and is calculated by analysing the activity between the right arm and left leg compared to the left arm

Question 25

What does the aVF lead Show and how is it calculated

Answer 25

This lead shows the inferior view of the heart and is calculated by analysing the activity between the right arm and left arm compared to the left leg

Question 26

What does a positive deflection on an ECG

Answer 26

A positive deflection shows that the electrical activity within the heart is travelling towards the lead

Question 27

What does a negative deflection on an ECG show

Answer 27

A negative deflection shows that the electrical activity within the heart is travelling away from the lead =

Question 28

What is each deflection on an ECG representing

Answer 28

Each deflection is a wave of the average electrical activity is traveling

Question 29

What does the height of the deflection show

Answer 29

The height of the deflection represents the amount of electrical activity flowing in that direction

Question 30

What is shown by the lead with the most positive deflection

Answer 30

The lead with the most positive deflection is the most aligned with the direction the hearts electrical activity is travelling

Question 31

What does it mean if the R wave is greater than the S wave

Answer 31

It suggests the depolarisation is moving towards the lead

Question 32

What does it mean if the S wave is greater than the R wave

Answer 32

It would suggest that the depolarisation is moving away from the lead

Question 33

What does it mean if the S and R wave are of equal heights

Answer 33

It means that the depolarisation is travelling at 90 degrees to the lead

Question 34

Different leads represent different anatomical territories of the heart what does this allow

Answer 34

This allows for pathology to be localised to a particular region of the heart

Question 35

Which leads show an inferior view of the heart

Answer 35

Leads II, III and aVF

Question 36

Which leads show a lateral view of the heart

Answer 36

Leads I, aVL, aVR, V5, V6

Question 37

Which leads show an anterior view of the heart

Answer 37

Leads V3 and V4

Question 38

Which leads show a septal view of the heart

Answer 38

Leads V1 and V2

Question 39

If an ECG shows an ST elevation which leads would be affected and what would it suggest

Answer 39

Leads to V3 and V4 which could suggest an anterior myocardial infarction

Question 40

Where does electrical activity start in the heart

Answer 40

At the sinoatrial node

Question 41

From the sinoatrial node where does the electrical activity spread to

Answer 41

The atrioventricular node

Question 42

From the atrioventricular node where does the electrical activity spread to

Answer 42

Spreads down the bundle of HIS and into the purkinje fibres

Question 43

What does the electrical activity in the purkinje fibres cause

Answer 43

The ventricular contraction

Question 44

What is a normal cardiac axis in a healthy individual

Answer 44

Lies between -30 degrees and +90 degrees

Question 45

In a normal cardiac axis in a healthy individual in which leads is overall electrical activity seen

Answer 45

In leads I, II and III

Question 46

In a normal cardiac axis of a healthy individual which leads has the most positive deflection

Answer 46

Lead II

Question 47

In a normal cardiac axis of a healthy individual which lead shows the most negative deflection and why

Answer 47

The aVR lead because it has a viewpoint of the heart from the opposite direction

Question 48

What causes right axis deviation

Answer 48

The direction of depolarisation is been distorted to the right between +90 and +180 degrees

Question 49

What is the most common cause of right axis deviation and how does it occur

Answer 49

Right ventricular hypertrophy. This occurs when there is extra right ventricular tissue resulting in a stronger electrical signal been generated by the right side of the heart this causes the deflection in lead I to become negative and the deflection on lead aVF and IIII to become more positive

Question 50

What is right ventricular hypertrophy most commonly associated with

Answer 50

Pulmonary hypertension but can be seen in very tall people

Question 51

What causes left axis deviation

Answer 51

Left axis deviation is caused by the direction of depolarisation being distorted to the left between -30 and -90 degrees

Question 52

How is left axis deviation showing in relation to the lead

Answer 52

The deflection of lead III becomes more negative

Question 53

When should left axis deviation be considered significant

Answer 53

Left axis deviation should only be considered significant if the deflection of lead II becomes negative

Question 54

What can cause left axis deviation

Answer 54

Conduction abnormalities

Question 55

What are the boundaries of a Normal Tachycardia Bradycardia Heart rates

Answer 55

Normal is 60-100 bpm Tachycardia is over 100 bpm Bradycardia is under 60 bpm

Question 56

How do you calculate a heart rate from an ECG of a regular heart rhythm

Answer 56

Count the number of large squares present in the PR Interval and then divide 300 by the number counted which gives you the heart rate

Question 57

How do you calculate heart rate from an ECG id the patient has an irregular heart rhythm

Answer 57

Count the number of complexes on the rhythm strip and multiple by 6

Question 58

There are 2 types of irregular heart rhythm… what are they

Answer 58

Regularly irregular Irregularly irregular

Question 59

What is meant when a patient has a regular irregular heart rhythm

Answer 59

The patients hear rhythm has a recurrent pattern of irregularity

Question 60

What is meant if a patient has a irregularly irregular heart rhythm

Answer 60

This patients heart rhythm is completely disorganised

Question 61

If P waves are present what should they be followed by

Answer 61

QRS Complex with a normal duration, direction and shape

Question 62

What happens if P waves are absent with an irregular heart rhythm

Answer 62

Atrial fibrillation

Question 63

How lon should the PR interval last for

Answer 63

Between 120-200m/s (3-5 small squares)

Question 64

If there is a prolonged PR interval what does this mean

Answer 64

There would be atrioventricular delay which could cause AV block

Question 65

How many types of heart block is there

Answer 65

4

Question 66

What are the 4 types of heart block

Answer 66

First degree heart block Second degree heart block type 1 Second degree heart block type 2 Third degree heart block

Question 67

What are the characteristics of first degree heart block

Answer 67

Fixed PR interval longer than 200 m/s (longer than 5 small squares)

Question 68

What are the characteristics of second degree heart block type 1

Answer 68

Progressive prolongation of the PR interval until the atrial impulse is no longer conducted and the QRS complex is dropped. AV condition resumes with the new beat and the sequence repeats

Question 69

What are the characteristics of seconds degree heart block type 2

Answer 69

Consistent PR interval duration with the QRS complex intermittently dropped due to a condition failure, this follows a repeating pattern at every 3rd or 4th P waves

Question 70

What is 3rd degree heart block also known as

Answer 70

Complete heart block

Question 71

What does complete heart block mean

Answer 71

There is non electrical communication between the atria and the ventricles which results in a complete failure of conduction

Question 72

How would compete heart block be represented on an ECG trace

Answer 72

There would be a presence of both P waves and QRS Complexes but they have no association with each other due to the atria and ventricles functioning independently

Question 73

What does it mean if in 3rd degree heart block the QRS complex lasts for less than 0.12s in duration

Answer 73

The signal originated above the bifurcation of the bundle of HIS

Question 74

WHAT DOES IT MEAN IF THE QRS Complex lasts longer that 0.12s in 3rd degree heart block

Answer 74

The signal originates fro below the bifurcation of the bundle of HIS

Question 75

What does it mean if a patient has a shortened PR interval

Answer 75

The P wave originated from somewhere closer to the AV node so the conduction takes less time Or The atrial impulse is getting to the ventricle by a faster shortcut instead of conducting slowly across the atrial wall, this is known as an accessory pathway associated with the delta wave