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CVS > 6 CVS ECG > Flashcards

6 CVS ECG Flashcards

1
Q

Do the cells of the conducting system of the heart have the abiltiy to contract?

A

No, they have the ability to generate an action potentials and conduct the impulse rapidly to all subendocardial regions of the ventricles.

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2
Q

Which layer of the ventricle contracts first?

A

ventricles depolarise from endocardium to epicardium (internal to external)

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3
Q

What is the point of having a conducting systemof the heart?

A

it enables coordinates contraction of atria and ventricles.

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4
Q

What rhythm does the sinoatrial node set?

A

the sinus rhythm (ie. normal)at a rate of 60-100 bpm

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5
Q

Where is the SA node located?

A

At the intersection between the Superior Vena cava SVC and the right atrium.

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6
Q

There is a fibrous ring between atria and ventricles, what does this imply?

A

Impulses must pass through the bundle of His to get to the ventricles. Only conducting path from Atria to ventricles.

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7
Q

Where are the right and left bundle branches located?

A

sub-endocardially in the interventriular septum

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8
Q

what are Purkinje fibres?

A

They are fine branches of the bundle of His.

Tehy spread the depolarisation throughout the ventricular myocardium very rapidly.

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9
Q

Why does the AV node contract more slowly than the SA node?

A

This enables ventricular filling before vetnricular contraction. Ie. time formatria to empty into ventricles.

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10
Q

Which part of the heart is the first to be depoalrised during ventricular depolarisation?

A

The interventricular septum

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11
Q

Which par of the heart is the last to contract during ventricular depolarisation?

A

The “base” this is the part of the ventricles just inferior to the atrioventricular valves. (the highest part og the ventricles)

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12
Q

During repolarisation of the ventricles, which part is repolarised first?

A

the base

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13
Q

What does an ECG record?

A

ECG records changes on the EXTRACELLULAR surface of the cardiac myocytes during wave of depolarisation and repolarisation

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14
Q

What is different between the cardiac cycle we studied and the ECG recording?

A

The cardiac cycle has been established by recordings made INSIDE cells. But ECGs are a recording of the external surface of cells.

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15
Q

If we place an electrode on our patient, and a depoalrisnig current comes towards it, what will the graoh look like?

A

We will see a POSITIVE, UPWARD deflection,

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16
Q

If an impulse (depolarising wave) is travelling away from our electrode, what do we observe on the graph?

A

a negative impulse

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17
Q

If the charge everywhere on our cell is the same, what do we see grpahically on our ECG reading?

A

A straight constant line on the baseline. The ECG picks uo a difference along the cell in term of potential!

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18
Q

What does a repolarising wave coming towards an electrode look like?

A

A negative downward deflection

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19
Q

If a repolarisation is moving away from our electrode, what do we graphically see on the ECG reading?

A

A positive, upward deflection

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20
Q

How does the ECG viewing vary with the angle at the which the impulse travels?

A

Repol/depol impulses coming straight towards the + electrode (view point) will give very STRONG, tall waves.
An impulse coming towards but slightly oblique, then get a smaller complex.

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21
Q

What happens if an impulse is travelling 90* angle across the viewpoint trajectory?

A

Then we either see

  • nothing, no complex
  • biphasic complex, little positive deflection, little negative delection,
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22
Q

What does a depolarisation wave going directly away from + electrode give as a reading?

A

a deep -ve complex

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23
Q

By which wave is sinoatrial node depolarisation translated?

A

None! We cant see SA node depolarisation because it emits insufficient signal to register on surface ECG!

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24
Q

By which ECG wave is atrial depolarisation indicated? (lead II reading)

A

the p wave, a small upward, positive deflection

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25
Q

Which wave does atrial depolarisation trigger?

A

p wave

26
Q

How is the delay at the AV node translated on an ECG reading? (lead II)

A

It is the isoelectric segment (flag line) between p and qrs complex.

27
Q

How is the spread of depolarisation from the atria to the ventricles translated on an ECG reading?

A

it is the passage through the Bundles of His and comtributes to isoelectric segment too (flat line between p and qrs)

28
Q

How is the depolarisation of the myocardium (ventricular) translated on an ECG reading?

A

QRS complex

29
Q

The first part of the heart to depolarise is the interventricular septum and it depolarises from left to right. How does this show on an ECG?

A

This depolarisation of the interventricular septum goes away from the apex (from which we are viewing the heart) so the wave is negative.
But not completey aligned with our view trajectory, so only small negative deflection.
This is the Q wave.

30
Q

How does the depolarisation of the apex and the free ventricular wall translate in an ECG?

A

Large upward deflection, the R wave.

  • upward because depolarisation moving directly towards electrode
  • large because of the muscle mass, so more electrical activity
31
Q

If elft ventricles was hypertrophied, how would the R wave change?

A

The r wave would be representing even more muscle cells, and so even more electrical activity, and so would be correspondingly taller.

32
Q

Hiw does the end of ventricular depolarisation translate onto an ECG?

A

The S wave.

  • downward because moving away
  • small because not moving directly away
33
Q

In which direction does repolarisation travel myocaridum thickness?

A

epicardium to endocardium

34
Q

How does ventricular repolarisation translate onto an ECG?

A

T wave. Medium upward deflection.
Repolarisation spreads in opposite direction to depolarisation.
- upward because wave of repolarisation moving away from the electrode

35
Q

Will qrs complex always be seen in a healthy patient?

A

No, not necessarily, it will be happening, but depending on the angle from which we are observing, may not see all components.

  • just qr
  • just rs
  • just r
  • just qs
36
Q

How many electrodes for an ECG?

A

10 electrodes

37
Q

How many limb electrodes in an ECG?

A

4

38
Q

How many chest electrodes in an ECG?

A

6 (V1-V6)

39
Q

How many views does a 10 electrode ECG give?

A

12 views, also called leads

40
Q

In which plane are the views offered by limb leads?

A

coronal, vertical

41
Q

Which leads look at the inferior surface of the heart?

A

II
III
AVF
=> These are the best leads to detect problems in the inferior surface of the heart, eg. mucle necrosis due to an inferior MI.

42
Q

Which coronary artery could most likely be responsible for an inferior MI?

A

Inferior border of the heart is mostly the right ventricle.

And the right ventricles is mostly supplied by the Right Coronary Artery

43
Q

Leads II, III and AVF are the best leads to look at the inferior border of the heart. What makes up this inferior border?

A 
essentially right (+ 
left) ventricles
44
Q

What relationship is tehre between aVR and lead II

A

they are the opposite of each other, ie. they are looking at the heart from different sides

45
Q

Which chest leads look mainly at the anterior and septum of the heart?

A

V1 and 2

46
Q

Which chest leads looks mainly at anterior apical region?

A

V3 and V4

47
Q

Which chest leads look mainly at the left lateral aspect of the heart?

A

V5 and V6

48
Q

What regions of the heart fact the anterior of the chest wall?

A

Right ventricle (and apex)

49
Q

Which coronary artery supplies the anterior aspect of the heart?

A

LAD and interventricular artery

50
Q

Where does the QT interval span from and to?

A

before Q to after T

51
Q

What does QT interval represent?

A

It tells us how long depolarisation and repolarisation are taking

52
Q

What is the normal range for the PR interval?

A

3-5 small boxes, ie. 0.12-0.20 seconds

53
Q

What does a prolonged delay between P wave and QRS complex signify?

A

AV node or His ischaemia? There is abnormal conduction delay between atria depolarisation and ventricular depolarisation.

54
Q

How long is a normal QRS complex?

A

< 3 small boxes, ie. <0.12 seconds

55
Q

With what non-pathological factor can QT interval vary?

A

heart rate

- and HR varies with respiratory rate

56
Q

How can we calculate the HR from a regular ECG?

A

We can count interval between R-R.

  • count big boxes between r waves
  • divide 300 by no of boxes
57
Q

If ECG show irregular HR, hiw do we calculate it?

A

We look at the number of QRS compexes in 6 seconds, the x10

- 6 seconds = 30 big boxes (6x5boxes)

58
Q

To be able to say if the rhythm is a normal sinus rhythm, we have to check 5 conditions, these are:

A
  1. HR 60-100
  2. Rhythm regular/irregular
  3. P wave, is there one before each QRS, and is there a QRS after each P
  4. PR interval 3-5 small boxes (0.12-0.20 sec)
  5. QRS <3 small boxes
59
Q

All the chest electrodes look at the heart in one plane, this is:

A

Transverse pane, horizontal

60
Q

Which limb leads look at the left side of the heart?

A

lead I and aVL

61
Q

How many views are given by 4 limb electrodes?

A

6 views or leads

62
Q

Which are the 6 leads (views) given by the 4 limb electrodes?

A

I, II, III

aVR, aVF, aVL

CVS (7 decks)

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