lecture 3: machanical properties of the heart : episode 2

Question 1

what are the two main phases of the heart beat?

Answer 1

systole

diastole

Question 2

what is diastole?

Answer 2

this is ventricular relaxation during which ventricles fill up with blood

4 sub phases

Question 3

what is systole?

Answer 3

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

2 sub phases

Question 4

what is the isovolumetric ventricular contraction?

Answer 4

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

Question 5

what is the end diastolic volume?

Answer 5

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

Question 6

what is the end systolic volume?

Answer 6

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

Question 7

what is the stroke volume?

Answer 7

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

Question 8

what is the ejection fraction?

Answer 8

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

this is normally 65%
heart failure means 35%

Question 9

what is the heart rate?

Answer 9

72 beats / min

Question 10

what was the cardiac output?

Answer 10

heart rate x stroke volume = 5.04 litres/min

Question 11

1. what is the anatomy of atrial systole?

Answer 11

• blood has passively been flowing through the valve into the ventricle
• but as atrial contraction happens this tops up the ventricular volume

Question 12

1. what is the pressure change of atrial systole?

Answer 12

• 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

Question 13

1. what is the ECG change and heart sound of atrial systole?

Answer 13

• P WAVE

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

Question 14

what causes valve incompetency ?

Answer 14

• pulmonary embolism
• congestive heart failure
• tricuspid incompetence

Question 15

2. what is the anatomy of isovolumetric contraction?

Answer 15

• 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

Question 16

2. what is the pressure change of isovolumetric contraction?

Answer 16

• 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

Question 17

2. what are the ECG changes and heart sounds of the isovolumetric contraction?

Answer 17

• QRS complex marks the ventricular depolarisation

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

Question 18

3. what is the anatomy of rapid ejection?

Answer 18

the aortic and pulmonary valve opens

Question 19

3. what is the pressure change of rapid ejection?

Answer 19

• 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

Question 20

4. what is the anatomy of reduced ejection?

Answer 20

the aortic and pulmonary valve start to close

Question 21

4. what is the pressure change of reduced ejection?

Answer 21

• 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

Question 22

4. what are the ECG changes and heart sounds of reduced ejection?

Answer 22

the T wave is due to ventricular re polarisation

Question 23

5. what is the anatomy of isovolumetric relaxation?

Answer 23

• the aortic and pulmonary valves have shut

Question 24

5. what are the pressure changes of isovolumentric relaxation?

Answer 24

• 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

Question 25

5. what are the ECG changes and heart sounds of isovolumic relaxation?

Answer 25

- the S2 sound is heard when the aortic and pulmonary valves shut

Question 26

6. what is the anatomy of rapid ventricular filling?

Answer 26

- atria ventricular valves open and the ventricles fill

Question 27

6. what are the pressure changes of rapid ventricular filling?

Answer 27

- ventricular volume increases while atrial pressure falls | - this time the filling is passive NOT isometric

Question 28

6. what are the ECG changes and heart sounds of rapid ventricular filling?

Answer 28

- an abnormal S3 sound might be heard which suggests turbulent ventricular filling

Question 29

what could turbulent ventricular filling be caused by?

Answer 29

- severe hypertension | - mitral incompetence

Question 30

what is the anatomy of reduced ventricular filling?

Answer 30

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

Question 31

what are the pressure changes of reduced ventricular filling?

Answer 31

the ventricular volume increases more slowly

Question 32

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

Answer 32

- 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

Question 33

what does the pulmonary artery wedge pressure measure?

Answer 33

- this measures the pressures in the heart by measuring in the pulmonary artery in the right side - measure the preload on the left side

Question 34

why does there PAWP become elevated?

Answer 34

problems with the left side of the heart

Question 35

what does a pressure volume loop compare?

Answer 35

ventricular pressure vs ventricular volume

Question 36

what is the EDV point?

Answer 36

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

Question 37

what is isovolumic contraction?

Answer 37

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

Question 38

why does the pressure fall?

Answer 38

this is due to isovolumic relaxation

Question 39

how does increasing pre load affect the stroke volume

Answer 39

increase in pre load | increase in SV

Question 40

what relationship does pressure and volume correlate with?

Answer 40

the frank starling relationship

Question 41

what does increasing the after load do?

Answer 41

this decreases the stroke volume | because increasing the after load decreases the amount of shortening

Question 42

what is the equation for cardiac output?

Answer 42

stroke volume x heart rate

Question 43

how do we change the stroke volume in this equation?

Answer 43

- change the preload - change the after load - change the contractility

Question 44

what is contractility?

Answer 44

- this is how forcefully the heart contracts

Question 45

what is the measure of contractility?

Answer 45

- the simple measure is the ejection fraction

Question 46

what increases contractility?

Answer 46

sympathetic stimulation