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LSS: cardiovascular system > lecture 3: machanical properties of the heart : episode 2 > Flashcards

lecture 3: machanical properties of the heart : episode 2 Flashcards

1
Q

what are the two main phases of the heart beat?

A

systole

diastole

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2
Q

what is diastole?

A

this is ventricular relaxation during which ventricles fill up with blood

4 sub phases

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3
Q

what is systole?

A

this is ventricular contraction when the blood is pumped into the arteries

2 sub phases

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4
Q

what is the isovolumetric ventricular contraction?

A

the pressure builds up in the ventricles during early systole but the ventricles only expel the blood when the pressure reaches the point where it overcomes the pressure of the after load

this period of time is known as the isovolumetric ventricular contraction

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5
Q

what is the end diastolic volume?

A

this is the volume of the ventricle at the end of ventricular filling
around 130 ml

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6
Q

what is the end systolic volume?

A

this is the volume left in the ventricle at the end of contraction
around 60ml

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7
Q

what is the stroke volume?

A

this is the volume of blood that is ejected by ventricular contraction

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8
Q

what is the ejection fraction?

A
  • this is the proportion of the end diastolic volume that is pumped out

this is normally 65%
heart failure means 35%

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9
Q

what is the heart rate?

A

72 beats / min

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10
Q

what was the cardiac output?

A

heart rate x stroke volume = 5.04 litres/min

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11
Q
  1. what is the anatomy of atrial systole?
A
  • blood has passively been flowing through the valve into the ventricle
  • but as atrial contraction happens this tops up the ventricular volume
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12
Q
  1. what is the pressure change of atrial systole?
A
  • atrial pressure shows a small increase due to the contraction
  • there might also be a small jugular pulse due to the atria contraction pushing some blood back up the jugular vein
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13
Q
  1. what is the ECG change and heart sound of atrial systole?
A
  • P WAVE

during this time we can hear the S4 heart sound which is caused by valve incompetency

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14
Q

what causes valve incompetency ?

A
  • pulmonary embolism
  • congestive heart failure
  • tricuspid incompetence
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15
Q
  1. what is the anatomy of isovolumetric contraction?
A
  • this is the contraction of the ventricles with no change in volume
  • contraction of ventricles against closed valves
  • AV valves closing and the semi-lunar valves opening
  • the ventricles are contracting isometrically so the muscle fibres are not changing length but they are generating force
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16
Q
  1. what is the pressure change of isovolumetric contraction?
A
  • the AV valve will shut as the ventricular pressure overtakes the atrial pressure
  • the ventricular pressure is reaching the aortic pressure
  • when the ventricular pressure is greater than the aortic pressure the aortic valve opens
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17
Q
  1. what are the ECG changes and heart sounds of the isovolumetric contraction?
A
  • QRS complex marks the ventricular depolarisation

- S1 (LUB) is heard due to the closure of atria ventricular vales

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18
Q
  1. what is the anatomy of rapid ejection?
A

the aortic and pulmonary valve opens

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19
Q
  1. what is the pressure change of rapid ejection?
A
  • the ventricles isotonically contract
  • the ventricular pressure rapidly increases and exceeds the aortic pressure so the semilunar valves open and ventricular volume decreases
  • the tricuspid valve is pushed into the atrium which causes a small increase in pressure in the jugular vein - c wave
20
Q
  1. what is the anatomy of reduced ejection?
A

the aortic and pulmonary valve start to close

21
Q
  1. what is the pressure change of reduced ejection?
A
  • as the blood has left the ventricles the ventricular volume and pressure begins to decrease
  • this means the semilunar valves to shut as the pressure gradient means blood starts to blood backwards from the arteries
22
Q
  1. what are the ECG changes and heart sounds of reduced ejection?
A

the T wave is due to ventricular re polarisation

23
Q
  1. what is the anatomy of isovolumetric relaxation?
A
  • the aortic and pulmonary valves have shut
24
Q
  1. what are the pressure changes of isovolumentric relaxation?
A
  • the atria have been filled with blood but due to the atrioventricular valves being shut the atrial pressure starts to rise
  • v wave is due to blood pushing the tricuspid valve which gives the second jugular pulse
  • there is a sharp increase in aortic pressure due to rebound pressure against the aortic valve as the aortic wall relaxes
25
Q
  1. what are the ECG changes and heart sounds of isovolumic relaxation?
A
  • the S2 sound is heard when the aortic and pulmonary valves shut
26
Q
  1. what is the anatomy of rapid ventricular filling?
A
  • atria ventricular valves open and the ventricles fill
27
Q
  1. what are the pressure changes of rapid ventricular filling?
A
  • ventricular volume increases while atrial pressure falls

- this time the filling is passive NOT isometric

28
Q
  1. what are the ECG changes and heart sounds of rapid ventricular filling?
A
  • an abnormal S3 sound might be heard which suggests turbulent ventricular filling
29
Q

what could turbulent ventricular filling be caused by?

A
  • severe hypertension

- mitral incompetence

30
Q

what is the anatomy of reduced ventricular filling?

A

diastasis: where the initial passive filling of the heart’s ventricles has slowed down, but before the atria contract to complete the active filling.

31
Q

what are the pressure changes of reduced ventricular filling?

A

the ventricular volume increases more slowly

32
Q

what is the difference between the left and the right side of the heart in terms of pressure?

A
  • the same pattern of pressure changes occurs in the right side of the heart
  • but the right side of the heart displays lower pressures than the left side of the heart
33
Q

what does the pulmonary artery wedge pressure measure?

A
  • this measures the pressures in the heart by measuring in the pulmonary artery in the right side
  • measure the preload on the left side
34
Q

why does there PAWP become elevated?

A

problems with the left side of the heart

35
Q

what does a pressure volume loop compare?

A

ventricular pressure vs ventricular volume

36
Q

what is the EDV point?

A

this is when the ventricles are full but they haven’t generated any isotonic pressure

37
Q

what is isovolumic contraction?

A

this is when the volume hasn’t changed but they isotonic contraction generates a large increase in pressure

38
Q

why does the pressure fall?

A

this is due to isovolumic relaxation

39
Q

how does increasing pre load affect the stroke volume

A

increase in pre load

increase in SV

40
Q

what relationship does pressure and volume correlate with?

A

the frank starling relationship

41
Q

what does increasing the after load do?

A

this decreases the stroke volume

because increasing the after load decreases the amount of shortening

42
Q

what is the equation for cardiac output?

A

stroke volume x heart rate

43
Q

how do we change the stroke volume in this equation?

A
  • change the preload
  • change the after load
  • change the contractility
44
Q

what is contractility?

A
  • this is how forcefully the heart contracts
45
Q

what is the measure of contractility?

A
  • the simple measure is the ejection fraction
46
Q

what increases contractility?

A

sympathetic stimulation

LSS: cardiovascular system (17 decks)

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