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CVS > Session 2: The Heart as a Pump > Flashcards

Session 2: The Heart as a Pump Flashcards

1 - Describe the basic anatomy of the heart naming all valves, chambers and major blood vessels. 2 - List the seven phases of the cardiac cycle stating the valve positions and blood flow for each phase. 3 - Interpret a Wiggers diagram of pressure and volume changes during the cardiac cycle. 4 - Define stroke volume and give typical values. 5 - Give the relative timings of systole and diastole at rest and understand how this changes with exercise. 6 - Explain the origin of the first and second he

1
Q

What do capacitance vessels do?

A

Enable system to vary the amount of blood pumped around the body.

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2
Q

What do resistance vessels do?

A

Restrict blood flow to drive supply to perfuse areas of the body.

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3
Q

The heart is in actuality two pumps, what does this mean?

A

That there is one pump consisting of the right atrium and the right ventricle and one pump consisting of the left atrium and the left ventricle.

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4
Q

Where is the pressure low and where is the pressure high in circulation?

A

In systemic circulation the pressure is high.

In pulmonary circulation the pressure is low.

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5
Q

What veins/arteries go in or out of the right atrium?

A

Superior and inferior vena cavae go in as well as the coronary sinus.

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6
Q

What veins/arteries go in or out of the right ventricle?

A

The pulmonary trunk which branches into the pulmonary arteries go out of the right ventricle.

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7
Q

What veins/arteries go in or out of the left atrium?

A

The pulmonary veins (4 of them) enters the left atrium.

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8
Q

What veins/arteries go in or out of the left ventricle?

A

The aorta leaves the left ventricle.

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9
Q

What is the typical pressure of the left atrium?

A

8 - 10 mm Hg

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10
Q

What is the typical pressure of the left ventricle?

A

120 in systole, 10 in diastole

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11
Q

What is the typical pressure of the aorta?

A

120 in systole, 80 in diastole

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12
Q

What is the typical pressure of the right atrium?

A

0 - 4 mm Hg

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13
Q

What is the typical pressure of the right ventricle?

A

25 systole, 4 diastole

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14
Q

What is the typical pressure of the pulmonary artery?

A

25 systole, 10 diastole

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15
Q

What is systole?

A

Contraction and ejection of blood from ventricles.

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16
Q

What is diastole?

A

Relaxation and filling of ventricles.

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17
Q

What are the specialised form of muscle found in the heart?

A

Cardiomyocytes. They are only found here and its called that they are in functional syncytium.

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18
Q

How long does an action potential last in the heart?

A

Around 280 ms. On action potential is a single contraction.

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19
Q

What are the valves called in the right part of the heart?

A

Between the right atrium and right ventricle there is a valve called the tricuspid valve (3 leaflets)
Between the right ventricle and the pulmonary trunk there is a valve called the pulmonary valve (3 leaflets)

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20
Q

What are the valves called in the left part of the heart?

A

Between the left atrium and the left ventricle there is a valve called the mitral valve or bicuspid valve (2 leaflets).
Between the left ventricle and the aorta there is a valve called the aortic valve.

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21
Q

What is the opening and closing of valves dependent on?

A

The pressure difference in the ventricles and atria. Higher ventricular pressure than atrial pressure will close the mitral/tricuspid valves. Higher ventricular pressure than aortic/pulmonary pressure will open the aortic/pulmonary valves.
Higher atrial pressure than ventricular pressure will open the mitral/tricuspid valves.

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22
Q

When the ventricular pressure in the left ventricle is higher than the pressure in left atrium the valves will close. How come they don’t flop over to the other side and cause regurgitation or retrograde flow in other words?

A

This is because of the chordae tendineae and the papillary muscles.

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23
Q

Explain what the chordae tendineae and the papillary muscles.

A

They prevent the inversion of valves on systole. The papillary muscles are what connects the chordae tendineae to the ventricular walls. The chordae tendineae are connected to the tricuspid and mitral valves.

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24
Q

Where can you find the pacemaker cells?

A

In the sinoatrial node.

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25
Q

How does atrial systole happen?

A

When an action potential spreads over the atria.

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26
Q

What happens at the atrioventricular node?

A

The action potential is delayed by around 120 ms to prevent the ventricles to beat at the same time as the atria.

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27
Q

What are seven phases of the cardiac cycle?

A

1 - Atrial contraction
2 - Isovolumetric contraction of the ventricle
3 - Rapid ejection of ventricle
4 - Reduced ejection
5 - Isovolumetric relaxation of ventricle
6 - Rapid filling
7 - Reduced filling

28
Q

What is the approximate total duration of the cardiac cycle?

A

Around 0.9s

29
Q

What happens to systole duration when the heart beats faster?

A

Nothing, it remains the same.

30
Q

What happens to diastole duration when the heart beats faster?

A

It decreases in duration.

31
Q

What happens in atrial contraction?

A

The atrial pressure rises as the atrium contracts. This is called the A wave. Atrial contraction only accounts for around 10% of the ventricular filling, this is the last filling. The mitral and tricuspid are open. The aortic and pulmonary are closed.

32
Q

Explain how atrial fibrillation relates to the atrial contraction.

A

In atrial fibrillation the atrial contraction does not work properly. This means that the final 10% filling will not work correctly, this is however something you can live with.

33
Q

What is the P wave?

A

It signifies onset of atrial depolarisation.

34
Q

What happens in isovolumetric contraction?

A

Mitral valve closes because the ventricular pressure exceeds the atrial pressure. There is a rapid rise in the ventricle as the ventricle contracts. There is however no change in the volume of the ventricle because the aortic valve is still closed. Mitral/tricuspid and the aortic/pulmonary are closed.

35
Q

What is the c wave?

A

When the mitral valve closes there is an increase in atrial pressure.

36
Q

What is the a wave?

A

The contraction of the atria.

37
Q

What does the QRS signify?

A

The onset of ventricular depolarisation.

38
Q

What is the S1 sound?

A

When the mitral valve and the tricuspid valve closes that is the first heart sound.

39
Q

Explain phase 3: rapid ejection.

A

When the ventricular pressure is higher than the aortic pressure as the ventricle contracts the aortic valve opens. This causes rapid ejection of the blood from the ventricle to the aorta. This causes a rapid decrease in the volume of the ventricle.

40
Q

What is x-descent?

A

The atrial pressure initially decreases because as the ventricle contracts the atrium is pulled downwards.

41
Q

What happens at the T wave?

A

Ventricle starts to repolarise.

42
Q

Explain phase 4: reduced ejection.

A

In the repolarisation of the ventricle and therefore the relaxation of the ventricle and rate of ejection begins to fall. Mitral/tricuspid is closed, aortic/pulmonary is open.

43
Q

What is the V wave?

A

When the atria gradually fills up with blood and the pressure increases due to the continuous returns from the lungs.

44
Q

Explain phase 5: Isovolumetric relaxation.

A

When the ventricular pressure falls below the aortic pressure there is a brief back flow of blood that causes the aortic valve to close. Although there is a rapid decline in the pressure of the ventricle, the ventricular volume will still be the same because all valves are closed.

45
Q

What is the dicrotic notch?

A

The aortic pressure slightly increases due to the closing of the aortic valve.

46
Q

What is stroke volume?

A

The amount of blood the pumped out of a ventricle per beat. End diastolic volume - End systolic volume. Usually around 120-40 -> 70-80 ml.

47
Q

How does S2 (second sound) come about?

A

When the aortic/pulmonary valves close.

48
Q

Explain phase 6: Rapid filling.

A

The mitral valve opens again causing a slight fall in atrial pressure (Y-descent). The mitral valve opens again because the ventricular pressure falls below the atrial pressure. Mitral and tricuspid are open but aortic and pulmonary are closed.

49
Q

What is S3?

A

The ventricular filling is normally silent from the mitral valve opening. However this can be heard sometimes. This is normal in children but it can be a sign of pathology in adults.

50
Q

Explain phase 7: reduced filling.

A

The rate of filling slows down called diastasis because the ventricle reaches its inherent relaxed volume. Further filling is driven by venous pressure.
At rest the ventricles are filled to 90% full by the end of phase 7.

51
Q

What is stenosis?

A

When the valves do not open enough.

52
Q

What is regurgitation/incompetence/insufficiency?

A

When the valves don’t close all the way.

53
Q

What are some causes of aortic valve stenosis?

A

Degenerative such as senile calcification or fibrosis.
Congenital such as a bicuspid formation of the valve instead.
Chronic rheumatic fever -> inflammation -> commissural fusion.

54
Q

Why are stenoses most common in the left side of the heart?

A

Because the pressure in the left side is higher than the right side.

55
Q

Explain aortic valve stenosis, the consequences of it.

A

Less blood can pass through the valve. This causes increased LV pressure and can also cause left sided heart failure. Increased LV causes LV hypertrophy. Left sided heart failure causes syncope (fainting) and angina (not enough blood to coronary arteries).
Also shear stress from cells being squeezed through the valve can cause shearing of the cells which is called microangiopathic haemolytic anaemia. This gives haemoglobinuria.

56
Q

How can you detect aortic valve stenosis?

A

Between S1 and S2 there will be a murmur in a shape of a diamond called the crescendo to decrescendo murmur.

57
Q

What are some causes of aortic regurgitation?

A

Aortic root dilation (leaflets pulled apart)

Valvular damage from usually endocarditis rheumatic fever.

58
Q

What happens at aortic regurgitation?

A

Blood flows back into LV during diastole.
This increases the stroke volume.
Systolic pressure increases.
Diastolic pressure decreases.
There’s a bounding pulse e.g. Quinke’s sign where the nail beds blush and get pale at the beat of the heart.
This also causes LV hypertrophy.

59
Q

How can you detect aortic valve regurgitation?

A

There’s an early decrescendo diastolic murmur meaning it’s from S2 to S1 and a bit in S1.

60
Q

What are some causes of mitral valve regurgitation?

A

This is usually a cause of the chordae tendineae muscle may not work properly to prevent prolapse in systole.
Damage to papillary muscle after heart attack
Left sided heart failure leads to LV dilation which can stretch valve.
Rheumatic fever can lead to leaflet fibrosis which disrupts seal formation.

61
Q

What is preload?

A

The end diastolic volume that stretches the right or left ventricle of the heart to its greatest dimension.

62
Q

How does preload release to mitral valve regurgitation?

A

As blood leaks back into LA this increases preload since more blood enters LV in subsequent cycles which can cause LV hypertrophy.

63
Q

How can you detect mitral valve regurgitation?

A

It’s a holosystolic murmur which means it’s a low volume sound that occurs between S1 to S2 (systole) but can sometimes somewhat spill over S2.

64
Q

What is the main cause of mitral valve stenosis?

A

The main cause is rheumatic fever which is around 99% of the cases. This causes commissural fusion of valve leaflets so its harder for blood to flow from left atrium to left ventricle.

65
Q

What are the consequences of mitral valve stenosis?

A

Increased LA pressure. This in its turn can cause LA dilation, pulmonary oedema, dyspnea and pulmonary hypertension which in their turn can cause right ventricular hypertrophy.
LA dilation can cause atrial fibrillation and oesophagus compression as well.
Atrial fibrillation can cause thrombus formation and oesophagus compression can cause dysphagia.

CVS (18 decks)

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