Electrocardiography

Question 1

What abnormalities can an ECG detect?

Answer 1

Conduction - issues with e- signals
Structural - e.g. hypertrophy
Perfusion - blood flow changes

Question 2

What are the advantages of an ECG?

Answer 2

Cheap,
Reproducible,
Quick

Question 3

What are electrodes

Answer 3

patches you place on patient’s skin

Question 4

What are cables

Answer 4

connection between electrode and machine

Question 5

What are leads

Answer 5

Views of the heart from electrodes and cables
12 leads

Question 6

What deflections are towards the +/-ve electrode

Answer 6

Upward deflection -> +ve
Downwards deflection -> -ve

Question 7

What is represented by the isoelectric line

Answer 7

No change in voltage

Question 8

What is denoted by the steepness of the deflection

Answer 8

Velocity of action potential

Question 9

What is denoted by the width of deflection

Answer 9

X axis = time .: shows duration of event

Question 10

In the cardiac cycle, what does the P wave represent?

Answer 10

Atrial Systole (atrial contraction)

Question 11

In the cardiac cycle, what does the QRS complex represent?

Answer 11

Ventricular Systole (ventricular contraction)

Question 12

In the cardiac cycle, what does the T wave represent?

Answer 12

Diastole (relaxation of ventricles, repolarisation)

Question 13

Why is repolarisation of the atria not seen

Answer 13

Hidden within the QRS complex

Question 14

Why does the AVN cause a slow speed of transduction

Answer 14

Allow time for ventricular filling after atrial contraction

Question 15

What structure is involved in the Q wave, and what is its function?

Answer 15

Bundle branches - Septal depolarisation

Question 16

Describe the vector of the Q wave

Answer 16

Towards negative electrode, so downward deflection

Question 17

What structure is involved in the R wave, and what is its function?

Answer 17

Purkinje Fibres - ventricular septal depolarisation

Question 18

Describe the vector of the R wave

Answer 18

Towards positive electrode (apex of heart), upward deflection

Question 19

What structure is involved in the S wave, and what is its function?

Answer 19

Purkinje fibres - late ventricular depolarisation (outer ventricle walls)

Question 20

Describe the vector of the S wave

Answer 20

Towards negative electrode (cardiac great vessels), downward deflection

Question 21

Describe the direction of Lead I

Answer 21

1 L: Right Arm to Left Arm

Question 22

Describe the direction of Lead II

Answer 22

2 Ls: Right Arm to Left Leg

Question 23

Describe the direction of Lead III

Answer 23

3 Ls: Left Arm to Left Leg

Question 24

What plane does Lead I/II/III use

Answer 24

Coronal

Question 25

What view does Lead I give

Answer 25

Lateral

Question 26

What view does Lead II/III give

Answer 26

Inferior

Question 27

What plane do the V electrodes use?

Answer 27

Axial/horizontal

Question 28

What is the position of V1?

Answer 28

Right sternal border in the 4th intercostal space

Question 29

What is the position of V2?

Answer 29

Left sternal border in the 4th intercostal space

Question 30

What is the position of V4?

Answer 30

Mid-clavicular line in the 5th intercostal space

Question 31

What is the position of V3?

Answer 31

Halfway between V2 and V4 (diagonal)

Question 32

What is the position of V5?

Answer 32

Anterior axillary line at the same level as V4

Question 33

What is the position of V6?

Answer 33

Mid-axillary line at the same level as V4

Question 34

What does the width of one big box on an ECG show?

Answer 34

0.2s

Question 35

What does the width of one little box on an ECG show?

Answer 35

0.04s

Question 36

What are the three active peripheral leads?

Answer 36

aVR, aVL, aVF

Question 37

Describe the location of these peripheral leads and how this relates to their naming

Answer 37

aVR (augmented vector right - from Right hand) aVL (augmented vector left - from Left hand) aVF (augmented vector foot - from the foot of the inverted triangle)

Question 38

Which leads use a coronal plane

Answer 38

Limb leads (I/II/III/aVL/aVR/aVF)

Question 39

Which leads use a Horizontal plane

Answer 39

Chest leads (V1-6)

Question 40

What leads give an inferior view RCA

Answer 40

Lead I/II/aVF

Question 41

What leads give an lateral view LCx

Answer 41

Lead I/aVL/V5/V6

Question 42

What leads give an antero septal view LAD

Answer 42

Lead V1/2 anterior - V3/V4

Question 43

What is the cardiac axis

Answer 43

Net direction of e- activity during depolarisation (R wave)

Question 44

Where would a normal cardiac axis be between?

Answer 44

90 and -30 degrees

Question 45

What region shows left axis deviation

Answer 45

-90º to -30º

Question 46

What region shows right axis deviation

Answer 46

90º to 180º

Question 47

what region shows extreme deviation

Answer 47

-90º to -180º

Question 48

How would you calculate the cardiac axis using Lead II and aVL?

Answer 48

STEP 1 - work out net deflection of Lead II (highest amplitude + lowest amplitude (negative) /// STEP 2 - work out the net deflection of aVL /// STEP 3 - draw a right angle triangle - hypotenuse is cardiac axis, adjacent is lead II, opposite is aVL /// STEP 3 - figure out SOHCAHTOA - should be tan but just double check /// STEP 4 - Do the SOHCAHTOA | find some qs and practice