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CVS Revision > 4 - The Heart as a Pump > Flashcards

4 - The Heart as a Pump Flashcards

1
Q

The heart is two pumps acting in ………..

A

Series

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2
Q

The systemic circulation is under …….. pressure

The pulmonary circulation is under …….. pressure

A

Systemic - high pressure

Pulmonary - low pressure

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3
Q

Overtime, ……….. ………… of the left and right sides of the heart is equal

A

Cardiac output

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4
Q

What is systole?

A

Contraction and ejection of blood from the ventricles

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5
Q

What is diastole?

A

Relaxation and filling of the ventricles

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6
Q

What is the average stroke volume?

A

~70ml blood per beat

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7
Q

Heart muscle cells operate in a …………. ………….. as they are electrically coupled by ……. junctions.

A

Functional syncytium

Gap

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8
Q

How long is a cardiac action potential?

A

~280 ms

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9
Q

How do the cusps of the mitral and tricuspid valves attach to the ventricular wall?

A

Valve cusps attached to papillary muscles on the ventricular wall via the chordae tendineae

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10
Q

What is the benefit of attachment of the AV valve cusps to the ventricular wall?

A

Prevent inversion of the valves and regurgitation of blood on systole

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11
Q

Where is the sinoatrial node?

A

In the wall of the right atrium - of muscular origin, not neuronal

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12
Q

How long is the conduction delay at the AV node?

A

~120 ms

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13
Q

Electrical excitation spreads through the ventricular myocardium from the …………….. surface to the ……………….. surface

A

Endocardial (inner) to epicardial (outer)

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14
Q

How long is systole at rest?

A

~0.35 s

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15
Q

How long is diastole at rest?

A

~0.55 s

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16
Q

What are the 7 phases 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

How do the relative durations of systole and diastole change during exercise?

A

Heart rate increases by decreasing the length of diastole, the time for systole is constant.

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18
Q

What wave of the ECG signifies atrial contraction?

A

The P wave

- Onset of atrial depolarisation

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19
Q

The small increase in pressure in the atria and ventricles associated with atrial contraction produces what section of the Wiggers diagram curve?

A

The A wave

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20
Q

Atrial contraction accounts for the final …….% of ventricular filling. The body can survive without this (e.g. in ………. ………………….)

A

10%

Atrial fibrillation

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21
Q

At the end of diastole, the ventricular volume is at its maximum, what is this called? What is the typical value in ml?

A

End-Diastolic Volume (EDV)

~120 ml

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22
Q

What occurs in isovolumetric contraction?

A
  • Ventricle begins to contract causing rapid rise in ventricular pressure
  • Mitral/tricuspid valve closes as the ventricular pressure exceeds atrial pressure
  • No change in volume (isovolumetric) as all valves are closed
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23
Q

What heart sound is caused by closure of the tricuspid and mitral valves?

A

S1

24
Q

During what phase of the cardiac cycle does the QRS complex of the ECG occur? What does it signify?

A

Isovolumetric contraction

Onset of ventricular depolarisation

25
Q

What wave is seen on the atrial pressure curve of a Wiggers diagram when then mitral valve closes?

A

C wave

- Small and transient increase in atrial pressure as the valve snaps shut

26
Q

What occurs during the rapid ejection phase of the cardiac cycle?

A
  • Ventricular pressure exceeds the aortic pressure and causes the aortic valve to open
  • Rapid decrease in ventricular volume as blood is ejected into the aorta
27
Q

There is a small drop in atrial pressure during the rapid ejection phase (X descent), what causes this?

A

The atrial base is pulled down toward the apex of the heart during ventricular contraction creating negative pressure in the atria

28
Q

What occurs in the reduced ejection phase?

A
  • Repolarisation of the ventricle leads to a decrease in tension
  • Rate of ejection falls
29
Q

During reduced ejection the atrial pressure gradually rises. What wave does this produce on a Wiggers diagram? Why does this occur?

A

V wave

- Atrial pressure rises due to venous return into the atria

30
Q

What ECG wave depicts ventricular repolarisation?

A

T wave

31
Q

What occurs during isovolumetric relaxation?

A
  • Ventricular pressure falls below aortic pressure
  • Brief backflow of blood closes the aortic valve
  • Rapid decline in ventricular pressure but all valves are closed so volume remain constant (isovolumetric)
32
Q

What part of the aortic pressure curve is caused by aortic valve closure?

A

Dicrotic notch

33
Q

There is always some residual blood left in the ventricles after contraction, what is this called?

A

End-Systolic Volume (ESV)

34
Q

What can the End-Diastolic Volume (EDV) and End-Systolic Volume (ESV) be used to calculate?

A 
Stroke volume (SV)
SV = EDV-ESV
35
Q

What heart sound is caused by closure of the aortic and pulmonary valves?

A

S2

36
Q

What occurs during the rapid filling phase of diastole?

A
  • When ventricular pressure falls below the atrial pressure the atrioventricular valves open
  • Rapid ventricular filling begins
37
Q

When the atrioventricular valves open, a small drop in atrial pressure occurs, what does this produce on the Wiggers diagram?

A

The Y descent on the atrial pressure curve

38
Q

Ventricular filling is usually silent. What heart sound can sometimes be heard? What causes this?

A

S3

Caused by rapid entry of blood from atria to ventricles (not a valve)

39
Q

When is the presence of S3 more likely to be pathological?

A
  • S3 is normal in children

- A sign of pathology (heart failure) in adults

40
Q

What occurs during the reduced filling phase of diastole?

A
  • Rate of filling slows down (diastasis)

- Ventricle reaches its relaxed volume with further filling driven by venous pressure

41
Q

At the end of the reduced filling phase the resting ventricles are …… % full. How does the remaining blood fill?

A

90%

- Remaining 10% from atrial contraction in the next cycle

42
Q

What is stenosis?

A

Obstruction to blood flow as the valve does not open enough

43
Q

What is regurgitation?

A

Valve doesn’t close all the way leading to backflow of blood when it should be closed

44
Q

What side of the heart is more likely to get abnormal valve function?

A

Left side - under higher pressures

45
Q

What causes aortic valve stenosis?

A
  • Degeneration with age (senile calcification/fibrosis)
  • Congenital (bicuspid form of valve)
  • Chronic rheumatic fever (inflammation and commissural fusion)
46
Q

What effect does aortic valve stenosis have on the heart?

A
  • Increased LV pressure = LV hypertrophy

- Left heart failure = syncope and angina

47
Q

What effect does aortic valve stenosis have on blood cells?

A
  • Shear stress due to turbulent flow moving through the aortic valve
  • Microangiopathic haemolytic anaemia
48
Q

What murmur can be heard due to aortic stenosis?

A

Crescendo-decrescendo murmur during systole (between S1 and S2)

49
Q

What causes aortic valve regurgitation?

A
  • Aortic root dilation (leaflets pulled apart)

- Valvular damage (e.g. endocarditis, rheumatic fever)

50
Q

What are the effects of aortic valve regurgitation on the heart?

A
  • Blood flows back into LV during diastole
  • Increases the stroke volume
  • Systolic pressure increases, diastolic pressure decreases (increase PP)
  • Bounding pulse
  • LV hypertrophy
51
Q

What murmur can be heard due to aortic valve regurgitation?

A

Decrescendo murmur in diastole (immediately after S2)

52
Q

What occurs in mitral valve regurgitation?

A
  • Chordae tendineae and papillary muscles fail to prevent prolapse of valve leaflets in systole
  • Blood leaks back into LA, increases preload as more blood will enter LV in the next cycle - leads to LV hypertrophy
53
Q

What causes mitral valve regurgitation?

A
  • Myxomatous degeneration - weakens leading to prolapse
  • Damage to papillary muscle after heart attack
  • Left heart failure = LV dilation - can stretch the valve
  • Rheumatic fever can lead to leaflet fibrosis
54
Q

What type of murmur can be heard is mitral valve regurgitation?

A

Holosystolic murmur (between S1 and S2)

55
Q

What occurs in mitral valve stenosis?

A
  • Commissural fusion of valve leaflets
  • Flow impaired between LA and LV
  • Increased LA pressure leads to pulmonary oedema, dyspnoea and pulmonary hypertension = RV hypertrophy
  • LA dilation leads to atrial fibrillation and oesophagus compression (dysphagia)
56
Q

What is the main cause of mitral valve stenosis?

A
  • Rheumatic fever (99.9% cases)
57
Q

What murmur is heard due to mitral valve stenosis?

A

Snap as the mitral valve opens and diastolic rumble

CVS Revision (8 decks)

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