Cardiac Cycle

Question 1

What are the 2 phases of a heart beat?

Answer 1

Systole + Diastole

Question 2

What is systole?

Answer 2

Ventricular contraction - ventricles generate pressure + eject blood into arteries

Question 3

What is diastole?

Answer 3

Ventricular relaxation - ventricles fill with blood

Question 4

How long does diastole last?

Answer 4

Approx. 2/3 of heart beat

Question 5

How long does systole last?

Answer 5

Approx. 1/3 of beat

Question 6

How many sub phases is diastole split into?

Answer 6

4

Question 7

How many sub phases is systole split into?

Answer 7

3

Question 8

What sub phase does the cardiac cycle start with?

Answer 8

Atrial systole

Question 9

What are the 4 sub phases of diastole?

Answer 9

• Isovolumetric Relaxation
• Rapid Passive Filling
• Slow Passive Filling
• Atrial Systole

Question 10

What are the 3 sub phases of systole?

Answer 10

• Isovolumetric Contraction
• Rapid Ejection
• Slow Ejection

Question 11

What is end-diastolic volume?

Answer 11

the volume of blood in the ventricles before contraction

Question 12

What is end-systolic volume?

Answer 12

the volume of blood in the ventricles after contraction

Question 13

What is stroke volume?

Answer 13

the volume of blood pumped from the left ventricle per beat

Question 14

How is stroke volume calculated?

Answer 14

end-diastolic volume - end-systolic volume

Question 15

What is ejection fraction?

Answer 15

k

Question 16

How is ejection fraction calculated?

Answer 16

(100*stroke volume) / end-diastolic volume

Question 17

What heart sound does atrial systole produce?

Answer 17

4th heart sound, but only abnormally - occurs w/ congestive heart failure, pulmonary embolism, tricuspid incompetence

Question 18

What is isovolumetric contraction?

Answer 18

interval between AV valves closing and SL valves opening + contraction of ventricles with no change in volume

Question 19

What signifies isovolumetric contraction on an ECG?

Answer 19

QRS complex

Question 20

What heart sound does isovolumetric contraction produce?

Answer 20

1st heart sound (“lub”) - due to closing of AV valves and associated vibrations

Question 21

What is rapid ejection?

Answer 21

ventricles contract pressure within them which exceeds pressure in aorta and pulmonary arteries + SL valves open, blood is pumped out and the volumes of ventricles decrease

Question 22

What signifies rapid ejection on an ECG?

Answer 22

gap between QRS complex + start of T wave (opening of SL valves also marks start of this phase)

Question 23

What heart sound does rapid ejection produce?

Answer 23

no heart sounds

Question 24

What is reduced ejection?

Answer 24

• reduced pressure gradient means SL valves start closing
• blood flow from ventricles decreases + ventricular volume decreases more slowly
• as pressures in ventricles < arteries, blood begins to flow back causing SL valves close

Question 25

What is reduced ejection?

Answer 25

- reduced pressure gradient means SL valves start closing - blood flow from ventricles decreases + ventricular volume decreases more slowly - as pressures in ventricles < arteries, blood begins to flow back causing SL valves close

Question 26

What does reduced ejection signify?

Answer 26

end of sytole

Question 27

What heart sound does reduced ejection produce?

Answer 27

no heart sounds

Question 28

What is isovolumetric relaxation?

Answer 28

SL valves CLOSE + atrial pressure continues to rise (AV valves only open when atrial pressure > ventricular pressure)

Question 29

What is the dichrotic notch?

Answer 29

an upstroke in aortic pressure when its descending - due to rebound pressure on the closed aortic valve as distended aortic wall relaxes

Question 30

What heart sound does isovolumetric relaxation produce?

Answer 30

2nd heart sound ("dub") - due to SL valves closing + associated vibrations

Question 31

What is rapid passive filling?

Answer 31

AV valves open + blood rapidly flows from atria to ventricles

Question 32

What signifies rapid passive filling on an ECG?

Answer 32

occurs in the isoelectric (flat) part of ECG after T wave

Question 33

What heart sounds are heard with rapid passive filling?

Answer 33

3rd heart sound - usually abnormal + may signify turbulent ventricular filling

Question 34

What could cause an abnormal 3rd heart sound?

Answer 34

turbulent ventricular filling - could be caused by severe hypertension or mitral incompetence

Question 35

What is reduced passive filling?

Answer 35

ventricular volume fills more slowly, ventricles still fill considerably without contraction of atria

Question 36

What is reduced passive filling also called?

Answer 36

diastasis

Question 37

How does pressure compare from the right to the left of the heart?

Answer 37

can reach a max of 120mg in the left side, can reach a max of 25mg in the right

Question 38

How do patterns of pressure changes compare from the right to the left of the heart?

Answer 38

essentially identical

Question 39

How does stroke volume compare from the right to the left of the heart?

Answer 39

both eject same volume despite lower pressures in the right

Question 40

Why does the right ventricle pump the same amount of blood as the left?

Answer 40

pumps into a lower pressure circuit

Question 41

What is the pressure difference in the systemic circuit vs. pulmonary circuit?

Answer 41

systemic circuit - 120/80 | pulmonary circuit - 25/5

Question 42

Describe a general pressure volume loop shape (from A to D).

Answer 42

From A, heads up to B, curves to the left to C, drops down to D

Question 43

What are graph axis and points ABCD for a general pressure volume loop?

Answer 43

``` x-axis = left ventricular volume y-axis = left ventricular pressure A = end-diastolic volume B = aortic pressure encountered C = end-systolic pressure ```

Question 44

What determines the preload that stretches the resting ventricular muscle?

Answer 44

blood filling the ventricles during diastole

Question 45

What blood pressures represent afterload?

Answer 45

blood pressures in greater vessels (aorta + PA)

Question 46

What blood pressures represent afterload?

Answer 46

blood pressures in greater vessels (aorta + PA)

Question 47

How can stroke volume be measured using the pressure volume loop?

Answer 47

horizontal linear distance between lines AB + CD

Question 48

How does stroke volume change with preload?

Answer 48

increase in preload = increase in stroke volume

Question 49

How does stroke volume change with afterload?

Answer 49

increase in afterload = decreases in stroke volume

Question 50

How is cardiac output calculated?

Answer 50

cardiac output = heart rate x stroke volume

Question 51

What 3 factors affect stroke volume?

Answer 51

preload, afterload, contractility

Question 52

What is contractility?

Answer 52

contractile capability (strength of contraction) of the heart

Question 53

How is contractility measured simply?

Answer 53

ejection fraction

Question 54

How can contractility be increased?

Answer 54

sympathetic stimulation

Question 55

How does increase in contractility affect ESPVR lines?

Answer 55

ESPVR line gets steeper than normal

Question 56

How does decrease in contractility affect ESPVR lines?

Answer 56

ESPVR line gets less steep than normal

Question 57

How does sympathetic stimulation increase contractility?

Answer 57

phosphorylate the Ca entry channel and Ca release channel => more release + more force