ECG

Question 1

What is the electrocardiograph?

Answer 1

Potential differences between distant sites on the body surface measurable by electrodes placed on the skin coupled to a sensitive recording device, the electrocardiograph.

Question 2

What is the term for a recording of potential differences between sites on the body surfaces?

Answer 2

Electrocardiogram (ECG or /EKG)

Question 3

What is a charge seperation called?

Answer 3

A dipole

Question 4

What does the dipole gnerate that are measurable with two electrodes?

Answer 4

Electrical field (line of isopotential)

Question 5

What is a lead axis?

Answer 5

The imaginary line connecting the two electrodes measuring the electrical field

Question 6

When is the measured potential difference the greatest?

Answer 6

When the lead axis is parallel to the direction of the dipole (electrical vector)

Question 7

What is the measured potential difference when the lead axis is perpendicular to the direction of dipole (electrical vector)?

Answer 7

0

Question 8

What represents an electrical vector?

Answer 8

The dipole

Question 9

What does the electrical vector have components of?

Answer 9

Magnitude (length of arrow) and direction (orientation of arrow)

Question 10

What is magnitude of electrical vectors determined by?

Answer 10

The mass of cardiac muscle that is involved in the generation of the signal.

Question 11

What is direction of electrical vectors determined by?

Answer 11

The overall activity of the heart any instant in time and varies during the cardiac cycle.

Question 12

What limb leads are bipolar?

Answer 12

The standard limb leads

Question 13

In lead I (RA to LA) - which is negative and which is positive?

Answer 13

RA is negative

LA is positive

Question 14

In lead II (RA to LL) - which is positive and which is negative?

Answer 14

RA is negative

LL is positive

Question 15

In lead III (LA to LL) - which is positive and which is negative?

Answer 15

LA is negative

LL is positive

Question 16

What king of deflection does depolarisation moving towards the recording electrode give?

Answer 16

An upward deflection

Question 17

Which leg is earthed for an ECG?

Answer 17

Right leg

Question 18

How long does the P wave last?

Answer 18

0.08 - 0.10 seconds

Question 19

In which part of the ECG is there action potential upstroke throughout atrial muscle?

Answer 19

P wave

Question 20

How long is the QRS complex?

Question 21

In which part of the ECG is there action potential upstroke throughout ventricular muscle?

Answer 21

QRS complex

Question 22

How long is the PR interval and what does it represent?

Answer 22

0.12 - 0.20 s

Represents largely AV node delay

Question 23

Which part of the ECG is maintained ventricular depolarisation? (sytole)

Answer 23

ST segment

Question 24

Which part of the ECG represents diastole?

Answer 24

TP intervale

Question 25

When is the ECG isoelectric?

Answer 25

During the PR interval, ST segments and TP interval

Question 26

Which leads are unipolar?

Answer 26

Augmented limb leads

Question 27

What is Goldberger's method?

Answer 27

One positive electrode, two others linked as negative

Question 28

What is the augmented voltage right (aVR)?

Answer 28

RA (+) to [LA & LF] (-)

Question 29

What is the augmented voltage left (aVL)?

Answer 29

LA (+) to [RA & LF] (-)

Question 30

What is augmented voltage food (aVF)?

Answer 30

LF (+) to [RA & LA] (-)

Question 31

What leads view the heart from a different angle compared to the standard limb leads (their axes subtend the angles of Einthoven's triangle)?

Answer 31

Augmented leads

Question 32

Where does electrical activity within the cardiac muscle cells cause current to flow?

Answer 32

Within the heart and the surrounding tissues

Question 33

aVR ianverted - describe the vector?

Answer 33

Predominant vector is depolarisation moving away from the electrode

Question 34

Poorly resolved P and T waves - describe vector?

Answer 34

Predominant vector is approximately perpendicular to the lead axis

Question 35

Descrive the vector in well resolved P and T waves?

Answer 35

Predominant vector is approximately parallel to the lead axis

Question 36

What polarity are chest (precordial) leads?

Answer 36

Unipolar

Question 37

What plane are the chest leads in and what plane are the limb leads in?

Answer 37

Chest leads - horizontal plane | Limb leads - frontal plane

Question 38

What should the calibration of ECG trace be?

Answer 38

Paper speed 25mm/sec

Question 39

In an ECG what is the y axis?

Answer 39

Amplitude

Question 40

In an ECG what is the x-axis?

Answer 40

Time

Question 41

What should the amplitude be measured in?

Answer 41

10mm/1mV

Question 42

What does one large box represent, in time and in amplitude?

Answer 42

0.2 seconds | 5mm amplitude

Question 43

What does one small block represent, in time and in amplitude?

Answer 43

0.04 seconds | 1mm of amplitude

Question 44

Give two methods of working out heart rate on an ECG?

Answer 44

1. 300/number of large squares between beats | 2. 300/numvber of large squares between R-R interval

Question 45

Which lead is usually the rhythm strip?

Answer 45

Lead II

Question 46

What is the rhythm strip and what does it allow you to detect?

Answer 46

Prolonged recording of one lead and allows you to detect rhythm disturbance

Question 47

What are the 7 steps in the practical approach to analysing the ECG?

Answer 47

(first determine the rhythm from the rhythm strip) 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 48

What three conditions does a normal resting ECG not exclude?

Answer 48

1. MI 2. Intermittent rhythm disturbance 3. Stable angina

Question 49

If intermittent rhythm disturbance is suspected, what do you do?

Answer 49

Do ambulatory ECG recording for 24 hours or 7 days

Question 50

If stable angina is suspected, what do you do and look for?

Answer 50

Do exercise ECG | Look for ST changes during/after exercise

Question 51

If the heart rate is irregular how do you work out the heart rate?

Answer 51

Count number of QRS complexes in 30 large squares and multiply by 10