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CVS > 2. The Heart As A Pump > Flashcards

2. The Heart As A Pump Flashcards

1
Q

Which vessel type are classed as ‘resistance vessels’, why is this?

A

Arteries, as they restrict blood flow to drive supply to hard to perfuse areas of the body

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2
Q

Which vessels act as capacitance vessels? How do they do this?

A

Veins

They enable the system to vary the amount of blood pumped around the body

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3
Q

Which valve is present between the right atria and right ventricle?

A

Tricuspid valve

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4
Q

Which valve is present between the left atria and ventricle?

A

Mitral valve

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5
Q

Define systole.

A

Contraction and ejection of blood from ventricles

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6
Q

Define diastole.

A

Relaxation and filling of ventricles.

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7
Q

What is stroke volume?

A

The amount of blood ejected per ventricle contraction

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8
Q

What is the average stroke volume?

A

70ml

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9
Q

What is the structure of cardiac muscle?

A

Striated
Branched
Intercalated discs between cells with gap junctions to allow action potentials to pass through myocardium easily.

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10
Q

An action potential in cardiac muscle increases the intracellular concentration of which ion?

A

Calcium

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11
Q

How does the length of the action potential in cardiomyocytes differ to others?

A

280ms

It is relatively long - lasts for the duration of a single contraction of the heart.

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12
Q

What is the function of the papillary muscles and chordae tendineae that attach to tricuspid and mitral valves?

A

Prevent inversion of the valves on systole when high pressures are exerted onto them.

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13
Q

What is the significance of atrioventricular delay?

A

Prevent the ventricles contracting at the same time as the atria, it gives them time to fill and allows atria to finish contracting.

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14
Q

How does the excitation spread through the ventricular myocardium?

A

Inner (endocardial) to outer (epicardial) surface

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15
Q

What happens to systole and diastole when heart rate increases?

A

Systole stays the same and diastole will shorten

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16
Q

Name the 7 stages of the cardiac cycle.

A
  1. Atrial Contraction
  2. Isovolumetric contraction
  3. Rapid ejection
  4. Reduced ejection
  5. Isovolumetric relaxation
  6. Rapid filling
  7. Reduced filling
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17
Q

What occurs during atrial contraction ?

A

Atria contract, accounting for the last 10-20% of ventricle filling.

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18
Q

What causes the ‘A wave’ in wiggers diagram?

A

Atrial pressures rising due to atrial systole.

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19
Q

What does the P wave on an ECG represent?

A

P wave signified the onset of atrial depolarisation.

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20
Q

What is the End-Diastolic Volume (EDV) and when is it reached?

A

It is the maximal ventricular volume, reached after atrial contraction in phase 1.

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21
Q

What is the typical EDV?

A

120ml

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22
Q

What causes the mitral valve to close during isovolumetric contraction?

A

The intraventricular pressure exceeds atrial pressure.

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23
Q

What wave is created on the atrial pressure curve when the mitral valve closes?

A

C wave

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24
Q

What does the QRS complex on an ECG signify?

A

The onset of ventricular depolarisation

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25
Q

What causes the first heart sound, S1?

A

Closure of the mitral and tricuspid valves during the isovolumetric contraction phase.

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26
Q

What pressure changes cause the aortic valve to open?

A

During rapid ejection phase, when the intraventricular pressure exceeds the pressure within the aorta.

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27
Q

What is aortic pressure during diastole?

A

80mmHg

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28
Q

What it the “X descent” on the atrial pressure curve?

A

A decrease in the atrial pressure as the ventricle contracts and the atrial base is pulled downwards.

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29
Q

What is the “V wave” on the atrial pressure plot?

A

A gradual rise in atrial pressure due to continued venous return from the lungs during reduced ejection phase.

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30
Q

Which ECG wave represents ventricular repolarisation?

A

T-wave

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31
Q

What causes the aortic valve to close during isovolumetric relaxation in phase 5 of the cardiac cycle?

A

When intraventricular pressure falls below aortic pressure, there is a brief backflow of blood which causes the aortic valve to close.

32
Q

What causes the “dicrotic notch” seen in the aortic pressure graph?

A

Increase in aortic pressure curve caused by the elastic recoil of the aorta following valve closure.

33
Q

How can stroke volume be calculated?

A

EDV-ESV= Stroke volume

34
Q

What is the average ESV?

A

80ml

35
Q

What causes the second heart sound, S2?

A

Closure of the pulmonary and aortic valve.

36
Q

When might you hear an S3 sound, what might this signify?

A

Sound of ventricular filling.

This is normal in children but can be a sign of pathology in adults

37
Q

What are 2 types of abnormal valve function?

A

Regurgitation and Stenosis

38
Q

What happens in stenosis of a valve?

A

The valve doesn’t open enough, so there is obstruction to blood flow.

39
Q

What is valve regurgitation?

A

The valve doesn’t close all the way, so there is back leakage when the valve should be closed.

40
Q

What are other names for valve regurgitation?

A

Incompetence or insufficiency

41
Q

What are 3 causes of aortic valve stenosis?

A
  1. Degenerative (senile calcification/fibrosis)
  2. Congenital (bicuspid form of valve)
  3. Chronic rheumatic fever (inflammation and fusion)
42
Q

What is the murmur associated with aortic valve stenosis?

A

Crescendo-decrescendo murmur

43
Q

How can aortic valve stenosis cause LV hypertrophy?

A

Less blood can get through the valve, so there is increased LV pressure, so the heart muscle hypertrophies

44
Q

In addition to LV hypertrophy, what else can aortic valve stenosis cause?

A

L-sided heart failure which can lead to syncope and angina (if not enough blood supplying heart muscle)

Shear stress on RBC’s - microangiopathic haemolytic anaemia.

45
Q

What are 2 causes of aortic valve regurgitation?

A
  1. Aortic root dilation (leaflets pulled apart)

2. Valvular damage (endocarditis rheumatic fever)

46
Q

Which valve abnormality is associated with a bounding pulse - head bobbing and Quinke’s sign?

A

Aortic valve regurgitation

47
Q

What happens during aortic valve regurgitation?

A

Blood flows back into LV during diastole, increasing stroke volume

48
Q

What is myxomatous mitral valve degeneration and what does it cause?

A

Weakening of the connective tissue which can cause valve prolapse

49
Q

What is the consequence of mitral valve regurgitation?

A

As some blood leaks back into the LA when the ventricle contracts, the preload is increased as more blood enters the ventricle in subsequent cycles, leading to LV hypertrophy.

50
Q

What is the most common cause of mitral valve stenosis?

A

Rheumatic fever (99.9% cases)

51
Q

What is the consequence of mitral valve stenosis?

A

Harder for the blood to flow into the LV, so increased pressure in the LA.

52
Q

What can increased pressure in the LA due to mitral valve stenosis cause?

A
  • pulmonary oedema
  • dyspnea
  • pulmonary hypertension
    These all lead to RV hypertrophy (harder to pump against the higher pressures)
  • LA dilation which can cause atrial fibrillation and oesophagus compression and dysphagia.
53
Q

Which valve is bicuspid?

A

Mitral valve

54
Q

What happens to ventricular pressure during isovolumetric contraction?

A

Rapid rise in pressure as ventricle contracts and all valves are still closed.

55
Q

What is the typical pressure in the right atrium?

A

0-4 mmHg

56
Q

What is the typical pressure in the LA?

A

8-10 mmHg

57
Q

What is the typical pressure in the pulmonary artery in diastole and systole?

A

10 diastole/ 25 systole

58
Q

What is the typical pressure in the left ventricle in diastole and systole?

A

10 diastole / 120 systole

59
Q

What is the typical pressure in the right ventricle during diastole and systole?

A

4 diastole/ 25 systole

60
Q

What is the typical pressure in the aorta during diastole and systole?

A

80 diastole / 120 systole

61
Q

When can aortic stenosis be heard? Explain why.

A

During systole, when the valve is open so the turbulent blood flow can be ausultated.

62
Q

What happens to diastolic pressure during aortic valve regurgitation?

A

Decreases as blood volume is lower as some has flowed back into LV.

63
Q

What happens to systolic pressure during aortic regurgitation?

A

Systolic pressure increases due to increased stroke volume - more blood in ventricles.

64
Q

Which valve pathology is associated with a bounding pulse?

A

Aortic valve regurgitation

65
Q

Aortic valve regurgitation also results in LV hypertrophy. Explain why.

A

Increased filling of the LV, increased systolic pressure so an increased workload.

66
Q

Which heart structures are usually responsible for preventing mitral valve regurgitation?

A

Papillary muscles and chordae tendineae prevent prolapse in systole

67
Q

Other than myxomatous degeneration, what else can cause mitral valve regurgitation?

A
  • Damage to papillary muscle after MI
  • left sided HF leads to LV dilation which can stretch valve
  • rheumatic fever can lead to leaflet fibrosis which disrupts seal
68
Q

Which valve pathologies result in a systolic murmur?

A

Aortic valve stenosis

Mitral valve regurgitation

69
Q

Which valve pathologies result in a diastolic murmur?

A

Mitral valve stenosis

Aortic regurgitation

70
Q

Explain why mitral valve stenosis can cause RV hypertrophy.

A

Increased pressure in the LA causes pulmonary oedema and pulmonary hypertension which increases the workload for the RV to pump the blood against.

71
Q

What is the approx length of diastole?

A

0.55 seconds

72
Q

What is the approximate length of systole?

A

0.35 seconds

73
Q

One heart beat is roughly _______ seconds.

A

0.9 seconds

74
Q

Where is the SA node and what is it’s function?

A

In the RA

Pacemaker cell of the heart - generate action potential spontaneously at regular intervals.

75
Q

What is cardiac output?

A

The volume of blood pumped per minute by the left ventricle.
Depends on HR and SV, which both vary.

76
Q

How might the heart sounds change during deep inspiration?

A

S2 can split into A2 (aortic valve closing) and P2 (pulmonary valve closing) as they are not in complete synchrony.

CVS (16 decks)

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