ECG

Question 1

How do potentials arise at body surface

Answer 1

Currents flow when membrane potential changes in repolarisation & depolarisation

Question 2

What happens when depolarisation moves towards a recording electrode

Answer 2

Upwards deflection on ECG

Question 3

What happens when depolarisation moves away from recording electrode

Answer 3

Downwards deflection of ECG

Question 4

What does no movement towards or away from recording electrode result in

Answer 4

NO deflection on ECG, Isopotential= every point has same potential (straight line)

Question 5

What is the triangle that standard leads I, II & III create

Answer 5

Einthoven’s

Question 6

What is RA, LA & LL

Answer 6

Right Arm
Left Arm
Left Leg
(right leg is neutral)

Question 7

What is lead I connecting

Answer 7

RA -‘ve to LA +’ve
(LA is recording electrode)

Question 8

What is lead II connecting

Answer 8

RA -‘ve to LL +’ve
(LL is recording electrode)

Question 9

What is lead III connecting

Answer 9

LA -‘ve to LL +’ve
(LL is recording electrode)

Question 10

What direction does lead II see the heart from

Answer 10

Inferior

Question 11

What does P wave represent & what direction

Answer 11

Atrial depolarisation
towards recording electrode

Question 12

What does QRS complex represent

Answer 12

Ventricular depolarisation

Question 13

What does Q wave show & direction

Answer 13

Left to right depolarisation of interventricular septum moving AWAY from recording electrode

Question 14

What does R wave show & direction

Answer 14

Main ventricular mass depolarisation TOWARDS recording electrode

Question 15

What does S wave show & direction

Answer 15

Ventricles at base of heart depolarise moving AWAY from recording electrode

Question 16

What is T wave & direction

Answer 16

Ventricular repolarisation
UPWARDS deflection as opposite direction to depolarisation

Question 17

What does PR interval in lead II tell us

Answer 17

Start of P to start of QRS
-Reflects time for SA node impulse to reach ventricles

Question 18

What is PR interval influenced strongly by

Answer 18

Delay in conduction through AV node

Question 19

What is the ST segment

Answer 19

From end of QRS complex to start of T wave
-Reflects isoelectric as when ventricles contract = systole

Question 20

What is QT interval

Answer 20

Start of QRS to end of T wave
-Reflects time of ventricular depolarisation & repolarisation

Question 21

What is TP segment

Answer 21

when ventricles relax= diastole

Question 22

What does standard 12 lead ECG compromise

Answer 22

3 standard limb leads (I, II & III)
3 augmented voltage (aV) leads
6 Chest leads

Question 23

What lead are bipolar and what are unipolar

Answer 23

bipolar = standard limb leads
unipolar= augmented voltage leads

Question 24

What are the 3 names of augmented voltage (aV) leads

Answer 24

aVR (for right arm)
aVL (for left arm)
aVF (for foot)

Question 25

What leads show vertical (frontal & coronal) direction & plane

Answer 25

Lead I, II, III, aVR, aVL & aVF

Question 26

which leads show horizontal (transverse) direction & plane of heart

Answer 26

Leads V1, V2, V3, V4, V5 & V6

Question 27

what 3 things does looking at all 12 leads help us do?

Answer 27

- Determine axis of heart in thorax -Look for ST or T changes in specific regions of heart = helpful in diagnosing ischaemic heart disease -Look for voltage criteria changes = crucial to diagnose chamber hypertrophy

Question 28

what do unipolar leads mean

Answer 28

One +'ve electrode (recording) that linked to 2 other -'ve

Question 29

What form aVR, aVL & aVF

Answer 29

aVR = RA (+) to LA & LF (-) aVL = LA (+) to RA & LF (-) aVF = LF (+) to RA & LA (-)

Question 30

What is a hexaxial reference system

Answer 30

total of 6 views from heart in frontal plane from standard & augmented limb leads

Question 31

where doe V1 lead go

Answer 31

4th intercostal space at right sternal edge

Question 32

where does V2 go

Answer 32

4th intercostal space at left sternal edge

Question 33

where does V4 go

Answer 33

5th intercostal space at left mid-clavicular line

Question 34

where does V3 go

Answer 34

between V2 & V4

Question 35

where does V5 go

Answer 35

Same horizontal level as V4 on left anterior axillary line

Question 36

where does V6 go

Answer 36

same horizontal level as V4 on mid-axillary line