ECG

Question 1

what is the device used to record the ECG?

Answer 1

an electrocardiograph

Question 2

what is the net dipole?

Answer 2

The progression of the +ve charge followed by the -ve charge, across the heart

Question 3

define lead?

Answer 3

the IMAGINARY line connecting two electrodes

Question 4

When is the recordedpotential difference greatest?

Answer 4

When the lead axis is parallel to the direction of the dipole (smallest/ 0mV when parallel to the lead axis)

Question 5

electrical vector

Answer 5

has components of magnitude an direction
(magnitude determined by the mass of cardiac muscle that is involved in the signal generation, and direction determined by the overall activity of the heart at any one instant, and varies over the cardiac cycle

Question 6

depolarisation moving towards the recording (+ve) electrode, gives an upwards deflection. True/ False?

Answer 6

True

away gives a downward deflection

Question 7

where is lead I placed?

Answer 7

RA +ve to LA -ve

Question 8

Where is lead II placed?

Answer 8

RA -ve to LL +ve

Question 9

Where is lead III placed?

Answer 9

LA -ve to LL+ve

Question 10

what is the fourth electrode on the RL for?

Answer 10

earthing the person

Question 11

wires?

Answer 11

these go from the electrode to the machine (wires are not the same thing as LEADS)

Question 12

P wave

Answer 12

upstroke through atrial muscle

Question 13

QRS complex?

Answer 13

upstroke through ventricular muscle

Question 14

T wave?

Answer 14

ventricular repolarisation (upward deflection because moving in a direction opposite to that of depolarisation)

Question 15

which parts of the ECG are isoelectric?

Answer 15

the flat parts

Question 16

PR interval?

Answer 16

largely due to AV nodal delay

Question 17

ST segment?

Answer 17

ventricular depolarisation (systole)

Question 18

TP interval?

Answer 18

diastole

Question 19

augmented leads?

Answer 19

these are unipolar, they view the heart from different angles compared to the standard limb leads

• augmented voltage R (aVR)
• augmented voltage left (aVL)
• augmented voltage foot (aVF)

Question 20

inverted wave?

Answer 20

-depolarisation is moving away from electrode

Question 21

poorly resolved wave?

Answer 21

vector is perpendicular to lead axis

Question 22

well resolved wave?

Answer 22

vector is parallel to lead axis

Question 23

chest leads?

Answer 23

• 6 more leads for 6 more views
• can look at body in transverse plane
• called “precordial” leads

Question 24

how many electrodes are involved in ECG?

Answer 24

9

Question 25

how many views of the heart (leads) are involved in ECG?

Answer 25

12 (not counting the earth electrode)

Question 26

what is the ECG Rhythm strip?

Answer 26

• prolonged recording of one lead
• usually lead 2
• allows detection of rhythm disturbance

Question 27

What are the 6 key steps to analysing an ECG?

Answer 27

1. Verify patient details: name and DOB
2. Check date and time ECG was taken
3. Check calibration of ECG paper
4. Determine the axis
5. Work out the rhythm (ask yourself 7 questions about the rhythm - which are in another flashcard)
6. Look at individual leads for voltage criteria changes OR any ST or T-wave changes

Question 28

What are the 7 questions you should ask yourself when working out the rhythm from an ECG?

Answer 28

1. Is electrical activity present?
2. Is the rhythm regular/ irregular?
3. What is the heart rate?
4. Are 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

what could an ECG still not detect?

Answer 29

• MI (may or may not cause ST elevation)
• intermittent rhythm disturbance (if suspected - for 24 hr for 7 days recording
• stable angina (do exercise ECG, look for ST changes which are absent at rest)