Cardiovascular mechanic II

Question 1

how do you work out stroke volume and ejection fraction?

Answer 1

end-diastolic volume - end-systolic volume = stroke volume.

ejection fraction= stroke volume/ end-diastolic volume * 100

Question 2

State the different phases of the cardiac cycle in order.

Answer 2

Atrial Systole: Atria contract to ‘top-up’ the volume of blood in ventricle
Isovolumic Contraction: Contraction but there is NO CHANGE in volume.
Rapid Ejection:
Reduced Ejection:
Isovolumic Relaxation
Rapid Ventricular Filling: Reduced Ventricular Filling;

Question 3

What is the Ejection Fraction?

Answer 3

SV/EDV - the proportion of the blood in the heart that is pumped out in one contraction

Question 4

What ECG change is seen in atrial systole?

Answer 4

P wave - atrial depolarisation

Question 5

What abnormal heart sound could be heard during atrial systole and what could it be a result of?

Answer 5

S4 - this could be due to tricuspid incompetence, pulmonary embolism or congestive heart failure

Question 6

How does atrial pressure change during atrial contraction?

Answer 6

Atrial pressure shows a small increase - a wave

Question 7

Describe the pressure and volume changes that take place during isovolumic contraction and when does it happen?

Answer 7

happens between the AV valves closing and semi-lunar valves opening.

• The valves are all closed so there is no change in volume but the pressure increases dramatically.
• due to ventricles contracting against closed valves, so NO change in volume which leads to increase in pressure

Question 8

What heart sound will be heard during isovolumic contraction?

Answer 8

S1 - closing of the atrioventricular valves

Question 9

What ECG change is seen during isovolumic contraction?

Answer 9

QRS complex - ventricular depolarisation

Question 10

Describe what happens during rapid ejection.

Answer 10

The ventricular pressure exceeds the aortic and pulmonary pressures (afterload) so the aortic and pulmonary valves open and blood
rapidly flows out into the aorta and pulmonary artery.

Question 11

What causes the ‘c wave’ in atrial pressure during rapid ejection?

Answer 11

The ventricles contracting pushes the tricuspid valve inwards causing a slight increase in atrial pressure - c wave

Question 12

Describe the electrical activity and heart sound heard during rapid ejection.

Answer 12

There is no electrical activity - isoelectric line on ECG. No heart sounds are heard.

Question 13

Describe what happens during reduced ejection.

Answer 13

Marks the end of systole. Ventricular pressure begins to fall T wave on the ECG due to the repolarisation of the ventricles. this is due to aortic and pulmonary pressure exceeding ventricular pressure and so the valves will begin to close.
There are NO heart sounds because none of the valves are shutting.

Question 14

What is the dichrotic notch and when does it occur?

Answer 14

The dichrotic notch is caused by the elastic recoil of the aorta causing a small rise in aortic pressure once ventricular contraction has ended.

Question 15

What changes in pressure occur during isovolumic relaxation?

Answer 15

The atrial pressure increases due to the filling against closed valves - v wave. Volume of the ventricles does not change.

Question 16

What heart sound can be heard during isovolumic relaxation?

Answer 16

S2 - this is due to the shutting of the aortic and pulmonary valves

Question 17

What changes in volume and pressure take place during rapid ventricular filling?

Answer 17

There is a gradual increase in ventricular volume but ventricular pressure remains about the same. Atrial pressure decreases.

Question 18

What abnormal heart sound can be heard during rapid ventricular filling and what could it be a result of?

Answer 18

S3 - can be due to mitral incompetence or severe hypertension

Question 19

What happens during reduced ventricular filling?

Answer 19

Ventricular volume increases more slowly. This is also called diastasis. There are NO changes on ECG and NO heart sounds.

Question 20

What diagram can show all this information?

Answer 20

Wiggers diagram

Question 21

What is the difference between the pressures in the pulmonary circulation and in the systemic circulation?

Answer 21

The pressures in the pulmonary circulation are much lower (though the patterns of pressure changes are the same)

Question 22

State the average pressures of the systemic circulation and of the pulmonary circulation.

Answer 22

Systemic - 120/80 Pulmonary - 25/5

Question 23

What is used to measure preload on the left side of the heart?

Answer 23

PAWP - Pulmonary Artery Wedge Pressure By measuring the pulmonary artery pressure you get an indirect measurement of the left atrial pressure

Question 24

What do points 1-4 on the pressure-volume loop indicate and what graph do you plot?

Answer 24

Plot ventricular pressure against ventricular volume.
1 = End diastolic volume: large ventricular volume
2 = Isovolumic contraction (pressure has increased but volume hasn’t)
3 = End systolic volume:
4 = Isovolumic relaxation (volume doesn’t change but pressure has decreased)

Question 25

Which feature of the pressure-volume loop indicates stroke volume?

Answer 25

Distance between point 2 and point 3

Question 26

Which points on the pressure-volume loop indicate preload and afterload?

Answer 26

Preload = point 1 (because it indicates the venous return to the heart and hence the stretch on the ventricular muscle) Afterload = point 2 (this is the end of isovolumic contraction when the pressure in the aorta and pulmonary artery (the afterload) is first experienced)

Question 27

Draw a diagram of the frank-starling relationship combined with a pressure-volume loop.

Answer 27

Starling’s Law = increased muscle fibres length causes increased ventricular contraction The graph should be force against muscle fibre length (and pressure against volume)

Question 28

How does the pressure-volume loop change if the venous return to the heart is increased?

Answer 28

Points 1 and 2 move further to the right so the distance between 2 and 3 and hence the stroke volume, increases

Question 29

How does the pressure-volume loop change if the afterload is increased?

Answer 29

increase afterload= decrease amount of shortening.

Question 30

What three factors can affect cardiac output?

Answer 30

Preload Afterload Contractility ( how forcefully it contracts)

Question 31

What is a simple measure of cardiac contractility?

Answer 31

Ejection Fraction

Question 32

How does the Frank-Starling Relationship change with increased contractility?

Answer 32

end diastolic volume INCREASES.
increase in stroke volume
point 1 and 2 are pushed to the right
point 3 and 4 pushed further to the left.
The gradient of the ESV line changes, to becoming more steeper