Cardiovascular mechanics 2

Question 1

What are the two main phases of the heart beat

Answer 1

Systole and Diastole

Question 2

What are the approximate time lengths of each phase

Answer 2

diastole = 2/3 of each beat
Systole = 1/3 of each beat

Question 3

How many phases is diastole split into

Answer 3

4

Question 4

How many phases is systole split into

Answer 4

3

Question 5

What are the three stages of systole

Answer 5

Isovolumetric contraction
Rapid ejection
Slow ejection

Question 6

What occurs during isovolumetric contraction

Answer 6

Interval between the AV valves closing and the semi-lunar valves opening.
Isometric contraction of the ventricles

Question 7

What occurs during rapid ejection

Answer 7

Aortic and pulmonary valves open

Ventricles contract. Pressure exceeds that in the aorta and the semilunar valves open and blood is pumped out

Question 8

What occurs during slow ejection

Answer 8

Reduced pressure gradient as the semilunar valves begin to close
Blood flow from the ventricles decreases and volume decreases slowly
Semilunar valves close

Question 9

Describe a typical ECG trace

Answer 9

P - atrial systole

QRS complex - ventricular depolarisation

Question 10

What are the 4 phases of diastole

Answer 10

isovolumetric relaxation
Rapid passive filling
Slow passive filling
Atrial systole

Question 11

Which diastolic phase is the longest

Answer 11

Slow passive filling

Question 12

What occurs during isovolumetric relaxation

Answer 12

Semilunar valves shut. Atrial pressure continues to increase, isometric relaxation of the ventricles (volume does not change)

Question 13

What occurs during rapid passive filling

Answer 13

The AV valves open and blood form the atria flow rapidly into the ventricle

Question 14

What occurs during slow passive filling

Answer 14

Ventricular volume fills more slowly but considerably

Question 15

What occurs during atrial systole

Answer 15

Atria are full from passive filling (pressure gradient) and the atria contract to top up the ventricular blood volume

Question 16

Explain the ‘Lub dub’ sound of the heart

Answer 16

Lub is from the atrioventricular valves closing (isovolumetric contraction)
Dub is from the semi-lunar valves closing (isovolumetric relaxation)

Question 17

What causes an abnormal third heart sound

Answer 17

Turbulent ventricular filling (severe hypertension or mitral incompetence) AKA ventricular gallop
Rapid filling phase

Question 18

What causes an abnormal fourth heart sound

Answer 18

Congestive heart failure, pulmonary embolism or tricuspid incompetence
Atrial systole phase

Question 19

What is the normal end diastolic volume

Answer 19

108 mL

Question 20

What is the normal end systolic volume

Answer 20

36 mL

Question 21

What is the normal stroke volume

Answer 21

72 mL

Question 22

What is the normal range of ejection fraction

Answer 22

60-70%

Question 23

How do you calculate stroke volume

Answer 23

End diastolic volume - end systolic volume

Question 24

How do you calculate ejection fraction

Answer 24

Stroke volume/end diastolic volume

Question 25

What is ejection fraction used for

Answer 25

Clinical sign of the vitality of the heart as it indicates how well the ventricles are contracting (heart failure 30-40%)

Question 26

How does patterns of pressure changes in the right and left of the heart relate

Answer 26

Right and left are identical

Question 27

How does pressure relate in the right and left of the heart

Answer 27

Pressure in the right heart and pulmonary circulation are much lower

Question 28

What is the difference in volume of blood ejected by the two sides of the heart

Answer 28

No difference, same volume despite the pressure difference

Question 29

Draw and label a pressure volume loop

Answer 29

A- end-diastolic volume B- C- end-systolic volume D

Question 30

What occurs from points A to B on a pressure volume loop

Answer 30

Isovolumetric contraction

Question 31

What occurs from points B to C on a pressure volume loop

Answer 31

Semi-lunar valves open as blood drains into the aorta. Slight pressure increase Rapid ejection

Question 32

What occurs from point C to D on a pressure volume loop

Answer 32

Isovolumetric relaxation, end systolic volume

Question 33

What occurs from point D to A on a pressure volume loop

Answer 33

Slow passive filling as the ventricles fill with blood

Question 34

Where is afterload encountered on a pressure volume loop

Answer 34

B

Question 35

What is the effect on a pressure loop when afterload increases

Answer 35

There is less shortening against the afterload, but a greater pressure generated to open the valve Width decreases and remains to the right while height increases

Question 36

Which factors affect stroke volume

Answer 36

Preload Afterload Contractility

Question 37

Define contractility

Answer 37

Contractile capability or strength of contraction of the heart

Question 38

What can increase contractility

Answer 38

SNS

Question 39

How is cardiac output calculated

Answer 39

Heart rate x Stroke Volume

Question 40

Draw the pressure volume loop for a heart with a hardened and narrowed aortic valve

Answer 40

Reduced width to the right and greater height as afterload is greatly increases

Question 41

Draw the pressure volume loop for a heart with a reduced venous return

Answer 41

Decreased preload so greater height and reduced width to the left

Question 42

Describe the pressure volume loop for a heart with SNS stimulation for venoconstriction and contractility

Answer 42

Much greater width and height