Intro To ECG

Question 1

What does an ECG provide information about?

Answer 1

Rate and rhythm
Chamber size
Electrical axis

Question 2

What is an ECG the main test for?

Answer 2

Myocardial ischaemia and infarction

Question 3

What causes current flow within tissue and surrounding tissue?

Answer 3

Electrical activity in and between (gap junctions) of myocytes

Question 4

What generates potential differences on the body surface?

Answer 4

Extracellular current

Question 5

Name of sensitive recording device

Answer 5

ElectrocardioGRAPH

Question 6

How an ECG works

Answer 6

Action potentials spread through conducting system and heart muscles in sequence, causing potential differences in different regions and makes up an electrical dipole

Theses potential differences are detected by electrodes on skin, which are linked to an electrocardiograph and then printed on an ECG

Question 7

What determines magnitude of electrical axis of heart?

Answer 7

Cardiac muscle mass (A+V dominate)

Question 8

What determines direction of electrical axis of heart?

Answer 8

Overall activity of heart at any time, which varies throughout the cycle

Question 9

ECG lead

Answer 9

Lead axis (imaginary line) between at least 2 electrodes
***not the wire

Question 10

Line generated on ECG when depolarisation moves towards positive/ recording electrode

Answer 10

Upward deflection

Question 11

Electrodes which lead I connects

Answer 11

RA-ve to LA+ve

Question 12

Electrodes which lead II connects

Answer 12

RA-ve to LL+ve

Question 13

Electrodes which lead III connects

Answer 13

LA-ve to LL+ve

Question 14

From what position does lead II view the heart?

Answer 14

Inferior position

Question 15

Which part of cardiac cycle does the P wave represent?

Answer 15

Atrial depolarisation, which spreads inferiority and left from SAN, thus moving towards electrode (upward deflection)

Question 16

Which part of cardiac cycle does the QRS complex represent?

Answer 16

Ventricular activation and depolarisation

Question 17

What direction is Q wave deflected? What causes this?

Answer 17

Downward deflection
Ventricular activation starts in intraventricular septum, moving to right thus depolarisation is moving away from recording electrode and results in downward deflection

Question 18

What direction is R wave deflected? What causes this?

Answer 18

Upward deflection

Main free walls of ventricles depolarise towards recording electrode

Question 19

What direction is T wave deflected? What causes this?

Answer 19

Upward deflection

Repolarising wave is spread away from recording device (think double negatives)

Question 20

Which part of cycle does the PR interval reflect?

Answer 20

SAN impulse to reach ventricles, which is influences by delay in AVN

Question 21

Why is elevation or depression in ST segment diagnostically important?

Answer 21

It is usually isoelectric (which means there should be no deflection)

Question 22

What does the QT interval reflect?

Answer 22

Ventricular depolarisation and repolarisation

Question 23

What comprises the 12 lead ECG?

Answer 23

3 standard limb leads
3 augment voltage (aV) leads
6 chest/ precordial leads

Question 24

Which leads help create a vertical/ coronal picture of heart?

Answer 24

augmented voltage and standard limb leads

Question 25

Which leads help create a horizontal/ transverse picture of heart?

Answer 25

precordial/ chest leads

Question 26

Standard limb leads are unipolar. True/ false?

Answer 26

False They are bipolar aV leads are unipolar

Question 27

Goldberger's Method

Answer 27

1 +ve electrode (recording) and 2 -ve linked electrode, positing the reference electrode in centre of heart where the recording electrode looks This is how augmented limb leads are linked

Question 28

Electrodes which aVR connects

Answer 28

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

Question 29

Electrodes which aVL connects

Answer 29

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

Question 30

Electrodes which aVF connects

Answer 30

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

Question 31

Hexaxial reference system

Answer 31

View of heart in frontal/ coronal plane provided by the standard and augmented limb leads

Question 32

What are lateral leads and which leads are lateral?

Answer 32

Lead I, aVL | The recording electrode is on the left arm and views heart from left

Question 33

What are inferior leads and which leads are inferior?

Answer 33

Lead II, III and aVF | Recording electrode is on left for and views heart from inferior direction

Question 34

aVR waves are negative. True/ false?

Answer 34

Depolarisation moving away from recording electrode is the predominant vector

Question 35

Where is V1 placed?

Answer 35

4th intercostal space, right sternal border

Question 36

Where is V2 placed?

Answer 36

4th intercostal space, left sternal border

Question 37

Where is V3 placed?

Answer 37

Halfway between V2 and V4

Question 38

Where is V4 placed?

Answer 38

5th intercostal space, left midclavicular line

Question 39

Where is V5 placed?

Answer 39

Left anterior axillary line, on same horizontal plane as V4 and V6

Question 40

Where is V6 placed?

Answer 40

Left midaxillary line, on same horizontal plane as V4 and V5

Question 41

Which chest electrodes are looking at the interventricular septum?

Answer 41

V1 and V2

Question 42

Which chest electrodes are looking at the anterior of the heart?

Answer 42

V3 and V4

Question 43

Which chest electrodes are looking at the lateral aspect/ left ventricle of the heart?

Answer 43

V5 and V6

Question 44

R wave progressively increases from V1 to V6 whereas S wave gradually decreases. True/ false?

Answer 44

True

Question 45

How to calculate HR from ECG trace

Answer 45

300/ number of large squares between beats (if regular rhythm) 300/number of large squares between R-R interval

Question 46

What is the rhythm strip and which lead usually shows this?

Answer 46

Prolonged reading of one lead which allows HR and cardiac rhythm to be identified Lead II

Question 47

What change is crucial for diagnosing chamber hypertrophy?

Answer 47

Voltage criteria changes

Question 48

What change is crucial in diagnosing Ischaemic Heart Disease?

Answer 48

Any ST segment or T wave changes in specific regions of heart

Question 49

Questions to consider when working out rate and rhythm using rhythm strip

Answer 49

1. is electrical activity present? 2. is the rhythm regular? 3. what is the HR? 4. is there a P-wave present? 5. what is the PR interval? 6. is each P-wave followed by a QRS-complex? 7. is the QRS duration normal?

Question 50

What is indicative of an MI in an ECG?

Answer 50

ST elevation MAY occur- doesn't always show up and therefore cannot always be diagnosed via an ECG

Question 51

Which significant heart diseases do not show up on a normal ECG?

Answer 51

MI may show up (ST elevation) Intermittent Rhythm Disturbance- if suspected do AECG for 24hr or 7 days Stable angina- if suspected, do exercise ECG