ECG

Question 1

What does ECG stand for?

Answer 1

Electrocardiogram

Question 2

What is an ECG?

Answer 2

Recording of electrical activity around the heart from body surface

Question 3

What does an ECG check? (7)

Answer 3

• Heart rhythm
• Electrical activity
• Heart rate
• Myocardium thickness
• Size and position of heat chambers
• Conduction system integrity
• Drug effects on heart

Question 4

How does an ECG create measurements?

Answer 4

Sensors attached to the skin detect electrical signals produced by the heart each time it beats

Question 5

What two parts of a depolarisation wave does an ECG measure? (2)

Answer 5

• Amplitude

- Direction

Question 6

What is an ECG representative of?

Answer 6

Electrical events of the cardiac cycle

Question 7

How are the electrical events of the cardiac cycle represented on the ECG cycle?

Answer 7

Characteristic waveform recorded graphically against time

Question 8

What are the 3 lead systems in a 12 lead ECG? (3)

Answer 8

• Limb leads
• Precordial/chest leads
• Augmented limb leads

Question 9

What are the limb leads in an ECG? (3)

Answer 9

• Lead I
• Lead II
• Lead III

Question 10

What are the chest/percordial leads? (6)

Answer 10

• VI
• V2
• V3
• V4
• V5
• V6

Question 11

What are the augmented limb leads? (3)

Answer 11

• avL
• avF
• avR

Question 12

What is a lead in an ECG? (2)

Answer 12

• Potential difference of electrical activity between two electrodes
  (Virtual)
• Shows heart electrical activity from particular angle

Question 13

What 3 limbs are used in an ECG? (3)

Answer 13

• Right arm
• Left arm
• Left leg

Question 14

What colour is a right arm electrode typically?

Answer 14

Red

Question 15

What colour is a left arm electrode typically?

Answer 15

Yellow

Question 16

What colour is a left leg electrode typically?

Answer 16

Black

Question 17

What limbs is lead I made up of? And which one is the positive/negative electrode?

Answer 17

• Left arm (positive)

- Right arm (negative)

Question 18

What do the limb leads represent on an ECG?

Answer 18

Potential difference between 2 limbs at a time

Question 19

Are limb leads bipolar/unipolar?

Answer 19

Bipolar

Question 20

What does a bipolar lead mean?

Answer 20

Electrodes registering voltage between 2 electrodes

Question 21

What does a unipolar lead mean? (2)

Answer 21

• Activity in heart directed towards/below electrode

- Potential difference between heart activity (positive recording electrode) and indifferent negative electrode

Question 22

What is the purpose of the lead connected to the right leg?

Answer 22

Reference electrode for recording purposes to complete electric circuit
Plays no role in ECG itself

Question 23

What is the purpose of the limb ECG leads?

Answer 23

Gives information on general heart activity and direction

Question 24

What is the purpose of the chest ECG leads?

Answer 24

Gives information on activity relative to area within the heart myocardium

Question 25

What limbs is lead II made up of? And which one is the positive/negative electrode?

Answer 25

- Right arm (negative) | - Left leg (positive)

Question 26

What limbs is lead III made up of? And which one is the positive/negative electrode?

Answer 26

- Left arm (negative) | - Left leg (positive)

Question 27

What triangle do the 3 limb leads form?

Answer 27

Equilateral eithoven's triangle

Question 28

What lead is usually used to form the rhythm strip?

Answer 28

Lead II

Question 29

Why is lead II used to form the rhythm strip?

Answer 29

P waves clearest here

Question 30

What is a positive deflection?

Answer 30

Depolarisation towards the positive electrode, above isolectric line

Question 31

What is a negative deflection?

Answer 31

Depolarisation away the positive electrode, below isoelectric line

Question 32

What is the purpose of the augmented chest leads?

Answer 32

Give additional means of info to identify directionality of waveform propagation across the heart

Question 33

Where is lead V1 placed?

Answer 33

Right hand side of sternum

Question 34

Where is lead V2 placed?

Answer 34

Left hand side of sternum

Question 35

Where is lead V3 placed?

Answer 35

3

Question 36

Where is lead V4 placed?

Answer 36

4

Question 37

Where is lead V5 placed?

Answer 37

5

Question 38

Where is lead V6 placed?

Answer 38

6

Question 39

What indicates the direction of electricity in the heart?

Answer 39

Towards the lead with the most positive deflection

Question 40

What is seen on an ECG when depolarisation is going towards a lead?

Answer 40

Positive deflection | R wave bigger than S (and Q) wave

Question 41

What is seen on an ECG when electricity is going away from a lead?

Answer 41

Negative deflection | R wave smaller than S (and Q) wave

Question 42

What is normal cardiac axis? (2)

Answer 42

- Between -30degrees and +90degrees

Question 43

What lead sees the most positive deflection in normal cardiac axis and why?

Answer 43

Lead II as this is at 5 oclock

Question 44

Draw the normal cardiac axis diagram

Answer 44

See notes

Question 45

Why direction does depolarisation normally happen in and why?

Answer 45

11 oclock to 5oclock | Apex is at that angle

Question 46

What lead sees the most negative deflection in normal cardiac axis and why?

Answer 46

aVR - opposite direction to lead II

Question 47

What deflections are seen in which leads in normal cardiac axis? (3)

Answer 47

- Positive lead I - Positive avF - Lead II most positive compared to I and III

Question 48

What deflections are seen in which leads in right axis deviation?

Answer 48

- Negative lead I | - Positive avF

Question 49

What deflections are seen in which leads in left axis deviation?

Answer 49

- Positive lead I - Negative avF - Extreme: positive lead II

Question 50

Give examples of conditions with right axis deviation

Answer 50

- Dextracardia (depolarisa | Right ventricular hypertrophy

Question 51

What causes left axis deviation?

Answer 51

Conduction defects and not by increased mass of the left ventricle.

Question 52

What height/amplitude is shown by a small square on an ECG? mm and mv

Answer 52

0.1mv=1mm

Question 53

What height/amplitude is shown by a large square on an ECG? mm and mv

Answer 53

0.5mv=5mm

Question 54

What time is shown by a small square on an ECG?

Answer 54

0.04 seconds

Question 55

What time is shown by a large square on an ECG?

Answer 55

0.2 seconds

Question 56

What is a normal value for PR interval? Seconds + squares

Answer 56

120 (0.12)-200ms (0.2secs) | 3-5 small sqs

Question 57

What is a normal value for QRS interval/width? Seconds + squares

Answer 57

80-120ms (0.12secs) | 3 small sqs

Question 58

What is a normal value for QT interval?

Answer 58

360-440ms

Question 59

What is QTc?

Answer 59

QT interval corrected for rate | = QT/R-R interval

Question 60

How is heart rate calculated using squares?

Answer 60

300 /Large squares R-R interval

Question 61

What is the normal level of variation in rhythm?

Answer 61

Less than 10% R-R interval

Question 62

Normal bpm?

Answer 62

60-100

Question 63

Calculating rate from an ECG if irregular rhythm?

Answer 63

Number of complexes on rhythm strip by 6

Question 64

How long is each rhythm strip?

Answer 64

10 seconds

Question 65

Order of reading ECG?

Answer 65

- Patient details - ECG date and time - HR - Heart rhythm - Cardiac axis - P waves (present, each followed by QRS, duration, direction, shape) - P-R interval (heart block) - QRS (Width/height) - ST segment - T waves (height? Inverted?)

Question 66

How to check heart rhythm (2)

Answer 66

- Mark out consecutive R-R intervals on a piece of paper | - Move them along the rhythm strip to check if the subsequent intervals are the same

Question 67

Normal QRS/T wave height? (2)

Answer 67

- 5mm limb leads | - 10mm chest lead

Question 68

What is checked for in P waves?

Answer 68

- Present - Each followed by QRS - Duration - Direction - Shape

Question 69

Normal P wave duration?

Answer 69

120-200ms