4: ECG theory and practice

Question 1

Electrical activity within and between cardiac mycocytes causes current ___.

Answer 1

flow

Question 2

How do electrical impulses travel between cardiac myocytes?

Answer 2

Gap junctions

Question 3

The electrocardio___ records the electrocardio___.

Answer 3

graph , gram

Question 4

What is a dipole?

Answer 4

A charge separation between areas of different charge (e.g in the heart)

Question 5

The measured potential difference is greatest when the lead is ___ to the direction of the dipole (electrical vector).

Answer 5

parallel

Question 6

The measured potential difference is zero when the lead is ___ to the dipole (electrical vector).

Answer 6

perpendicular

Question 7

Depolarisation moving towards the +ve electrode in an ECG lead gives…

Answer 7

upward deflection

Question 8

Depolarisation moving away from the +ve electrode in an ECG lead gives…

Answer 8

downward deflection

Question 9

Repolarisation moving towards the +ve electrode in an ECG lead gives…

Answer 9

downward deflection

Question 10

Repolarisation moving away from the +ve electrode in an ECG lead gives…

Answer 10

upward deflection

Question 11

How many electrodes are used in a standard ECG?

Answer 11

10

Question 12

How many leads does a standard ECG have?

Answer 12

12

Question 13

Where is the V₁ chest electrode placed?

Answer 13

Right sternal edge, 4th intercostal space

Question 14

Where is the V₂ chest electrode placed?

Answer 14

Left sternal edge, 4th intercostal space

Question 15

Where is the V₄ chest electrode placed?

Answer 15

Mid-clavicular line, 5th intercostal space

i.e the apex

Question 16

Where is the V₃ chest lead placed?

Answer 16

In between V₂ and V₄

Question 17

Where is the V₅ chest electrode placed?

Answer 17

Anterior axillary line, same horizontal line as V₄

Question 18

Where is the V₆ chest electrode placed?

Answer 18

Mid-axillary line, same horizontal line as V₄

Question 19

Which interval on an ECG represents systole?

Answer 19

ST segment

Question 20

Which interval on an ECG represents diastole?

Answer 20

TP segment

Question 21

How would you calculate heart rate using the squares on ECG paper?

Answer 21

Heart rate = 300 / number of large squares in RR interval

Question 22

What is the ECG rhythm strip?

Answer 22

Prolonged recording of one lead (usually Lead II)

Allows you to detect rhythm disturbances

Question 23

What type of disease does ST segment / T wave changes indicate?

Answer 23

Ischaemic heart disease

Question 24

What can voltage criteria changes be used to diagnose?

Answer 24

Chamber hypertrophy

Question 25

What is the first key step when analysing an ECG?

Answer 25

Verify patient details: name and date of birth

Question 26

After verifying a patient’s name and DOB, what else should be checked on an ECG?

Answer 26

Date and time ECG was taken

Question 27

What should you check before trying to determine heart rate / voltage criteria from an ECG?

Answer 27

The calibration of the ECG paper

Question 28

When working out heart rhythm from an ECG rhythm strip, you should ask yourself seven questions - what are they?

Answer 28

1. Is electrical activity present?
2. Is the rhythm regular or irregular?
3. What is the heart rate?
4. P-waves present?
5. What is the PR interval?
6. Is each P-wave followed by a QRS complex?
7. Is the QRS duration normal?

Question 29

Name three diseases which a normal ECG wouldn’t exclude.

Answer 29

Myocardial infarction

Intermittent rhythm disturbance

Stable angina