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My LSS- CVS > CVS3: Mechanical properties of the heart 2 > Flashcards

CVS3: Mechanical properties of the heart 2 Flashcards

1
Q

What are the two main phases of the heart beat?

A 
DIASTOLE= ventricular relaxation during which the ventricles fill with blood
SYSTOLE= ventricular contraction when the blood is pumped into the arteries
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2
Q

What is isovolumetric contraction?

A

You get contraction but no change in volume so you get a build up of pressure in the ventricles

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3
Q

When do you get an expulsion of blood in isovolumetric contraction?

A

The ventricles don’t expel blood until the pressure gets to the point where it overcomes the pressure of the after load.

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4
Q

What is the end diastolic volume?

A

The volume in the ventricles just before the ventricles expel blood

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5
Q

What is the end systolic volume?

A

The volume in the ventricles after the ventricle has completely contracted and expelled as much blood as it can

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6
Q

What is stroke volume?

A

EDV- ESV

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7
Q

What is the ejection fraction?

A

SV/EDV

The proportion of the end diastolic volume that is pumped out of the heart

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8
Q

What are the seven stages of the cardiac cycle?

A
  1. Atrial Systole
  2. Isovolumic contraction
  3. Rapid ejection
  4. Reduced ejection
  5. Isovolumic relaxation
  6. Rapid ventricular filling
  7. Reduced ventricular filling
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9
Q

What happens just before atrial systole in terms of blood flow?

A

Blood flows passively through the open AV valves into the ventricles

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10
Q

What happens during atrial systole in terms of blood flow?

A

The atria contract, topping off the volume of blood in the ventricles

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11
Q

Which part of the ECG indicates atrial systole?

A

The P wave= atrial excitation

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12
Q

Why might you hear a sound during atrial systole?

A

This is an abnormal heart sound called S4 which is caused by valve incompetency which makes the blood flow become turbulent.

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13
Q

When does S4 occur?

A
  • pulmonary embolism
  • Congestive heart failure
  • Tricuspid incompetence
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14
Q

Which pulse might you feel during atrial systole

A

Th jugular pulse- due to atrial contraction pushing some blood back up the jugular vein

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15
Q

When is isovolumic contraction?

A

Between the AV valves closing and the semi-lunar valves opening

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16
Q

What happens during isovolumic contraction?

A

Ventricles are sealed off

Ventricles contract with no change in volume

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17
Q

What happens to the pressure during isovolumic contraction?

A
  • The volume stays the same because the valves are closed but contraction of ventricles => rapid increase in pressure
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18
Q

What is seen on the ECG during isovolumic contraction?

A

The QRS complex= ventricular excitation

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19
Q

Which sound is heard during the isovolumic contraction stage and why?

A

S1 (lub) sound= closing of the AV valves because ventricular pressure> atrial pressure

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20
Q

Is the isovolumic stage isometric or isotonic?

A

Isometric- muscle fibres aren’t changing length but are generating force and increasing the pressure

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21
Q

What causes the rapid ejection phase?

A
  • The ventricles contracting in a closed chamber causes the ventricular pressure to exceed aortic/ pulmonary pressure (after load)
  • so the SL valves open and blood is pumped out
  • and ventricular volume decreases
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22
Q

Why causes the ‘c wave’ seen in the atrial pressure?

A

Right ventricular contraction pushes the tricuspid valve into the atrium and creates a small wave into the jugular vein

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23
Q

What is seen on the ECG and heard during occultation of the rapid ejection phase?

A

No ECG wave- because electrical excitation has already happened
No heart sounds- no closing of valves

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24
Q

What happens to the pressure during the reduced ejection phase?

A

The pressure of the ventricles fall below the arterial pressure

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25
Q

What is the result of the fall in ventricular pressure?

A

Ventricular pressure < Arterial pressure = blood begins to flow back causing the SL valves to begin closing

26
Q

What is seen on an ECG and heard during oscultation of the reduced ejection stage?

A

ECG: cardiac cells begin to REPOLARISE (AP returns to resting potential) = T wave
Sounds: NO SOUND (valves haven’t closed yet)

27
Q

What happens to the valves during isovolumic relaxation?

A
  • aortic/ pulmonary valves close

- AV valves remain closed

28
Q

Why is this stage called isovolumic relaxation?

A

AV valves are closed so no change in volume

29
Q

What happens to the atrial pressure during isovolumic relaxation?

A

Atria fills with blood but AV valves are shut so you get an INCREASE in atrial pressure

30
Q

What causes the v wave in the isovolumic relaxation stage?

A

Blood pushing the the tricuspid valve giving a second jugular pulse

31
Q

What causes the dichrotic notch in atrial pressure?

A

Rebound pressure against the aortic valve as the distended aortic wall relaxes

32
Q

What are the key events in the rapid ventricular filling stage?

A
  • AV valves opening
  • blood flow from atria to ventricles (passive- no contraction)
  • increase in ventricular volume
  • decrease in atrial pressue
33
Q

What might be heard during the rapid ventricular filling stage? and what does this indicate

A

S3 might be heard= abnormal heart sound.

Caused by turbulent ventricular filling

34
Q

What is S3 also called?

A

Ventricular gallop

35
Q

Which conditions cause S3?

A
  • severe hypertension

- mitral incompetence

36
Q

What happens during the reduced ventricular filling stage?

A
  • Slow filling of ventricles

- gradual increase in volume of ventricles

37
Q

What is the reduced vetricular filling stage also known as?

A

Diastasis

38
Q

Which diagram can be used to present the cardiac cycle information?

A

The Wiggers diagram

39
Q

Compare and contrast the pulmonary and systemic circulation

A

SAME:

  • same pattern of pressure changes
  • same volume of blood ejected

DIFFERENT:
- On the right side, have lower pressures than left

40
Q

What is the pulmonary artery wedge pressure?

A
  • lodging a balloon catheter into the pulmonary artery
  • blocking off the artery so no blood can go past
  • by measuring pressure on right side of the heart, you can measure preload on left side of the heart
41
Q

What are the x and y axes of the pressure- volume loops?

A 
x= ventricular volume
y= ventricular pressure
42
Q

What is the first point on the pressure-volume loop?

A

End diastolic volume= high volume in ventricles but hasn’t generated any pressure

43
Q

What is the second point on the pressure- volume loop?

A

Isovolumic contraction= volume doesn’t change but pressure generated increases

44
Q

What is the third point on the pressure volume loop?

A

End systolic volume= ventricles have contracted and start to expel blood. The volume of blood in the ventricles begins to fall and the ventricular pressure rises then falls

45
Q

What is the fourth point on the pressure volume loop?

A

Isovolumic relaxation= pressure in ventricles decreases but volume stays the same

46
Q

How do you calculate the stroke volume from a pressure volume loop?

A

Volume of Point 2 - volume of point 3

47
Q

What determines preload?

A

Preload= determines the stretch on muscles. Blood filling ventricles during diastole determines the preload.

48
Q

How can we determine preload from a pressure-volume loop?

A

Point 1 (EDV) gives an idea of preload because it is the volume of blood filling the ventricles and stretching the resting ventricular muscle

49
Q

What determines after load?

A

Its is the pressure in the aorta that the ventricle has to overcome to eject blood

50
Q

How can after load be determined from a pressure volume loop?

A

Afterload is JUST AFTER point 2 when the left ventricle encounters the aortic pressure when the aortic valve begin to open

51
Q

What form the axes for the Frank-Starling relationship in vivo?

A

x-axis: Instead of muscle fibre length we have volume

y-axis: Instead of force we have pressure

52
Q

What happens to stroke volume if we increase preload?

A

Points 1 and 2 are higher so distance between P3 and P2 increases= SV increases and EDV increases.
Greater preload= more contraction

53
Q

What happens to stroke volume if we increase afterload?

A
  • Increasing afterload= decreases the amount of shortening.
  • More pressure needed to open the aortic valve so P2 moves up the graph (in y-direction)
  • So stroke volume decreases
54
Q

When might after load increase?

A

If you have high blood pressure (hypertension)

55
Q

Which three factors affects stroke volume?

A

Changing the amount of blood that returns to the heart:
1. Preload
2. Afterload
Altering how forcefully the heart contracts (by using adrenaline)
3. Contractility

56
Q

Define cardiac contractility

A

Contractile capability (strength of contraction) of the heart

57
Q

Which measure can be used to determine cardiac contractility? And what increases cardiac contractility?

A

Ejection fraction

Sympathetic stimulation

58
Q

What happens to the in vivo Frank Starling relationship when contractility is increased?

A

More blood is pumped out
SV increases
P3 moves further to the left

59
Q

What happens to contractility and EDV during exercise?

A
  • contractility increases because of an increase in sympathetic activity
  • venoconstriction and muscle pump means EDV increase and more blood is returned to the heart
60
Q

What happens to the Frank Starling relationship during exercise?

A
  • P1 and 2 move further to the right because EDV increases
  • P3 and 4 move further to the left because of the increase in contractility
  • Difference between P2 and P3 increases= increase in SV

My LSS- CVS (21 decks)

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