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Cardiology > Cardiac Cycle > Flashcards

Cardiac Cycle Flashcards

1
Q

How long does the cardiac cycle last?

A

0.8 seconds

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2
Q

What are the two main phases of a heartbeat?

A

Diastole

Systole

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3
Q

What are the features of diastole?

A

Lasts approximately 2/3 of each beat

Ventricular relaxation
The ventricles fill with blood

Split into 4 distinct phases

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4
Q

What are the features of systole?

A

Lasts approximately 1/3 of each beat

Ventricular contraction
Ventricles generate pressure then eject blood into the arteries

Split into 3 distinct phases

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5
Q

What are the phases of the systole?

A

Isovolumetric contraction
Rapid ejection
Slow ejection

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6
Q

What is end-diastolic volume?

A

When the heart is filled

108ml

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7
Q

What is end-systolic volume?

A

Volume of blood after contraction

36ml

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8
Q

What is the stroke volume?

A

Difference between end-diastolic and end-systolic volume

72ml

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9
Q

What is ejection fraction?

A

Percentage of blood that is pumped into circulation
Describes the action and contractility of the heart

around 67%

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10
Q

What are the stages of diastole?

A 
Atrial systole
(Systole)
Isovolumetric relaxation
Rapid passive filling
Slow passive filling
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11
Q

What does the cardiac cycle being with?

A

Atrial systole

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12
Q

What is atrial systole on an ECG?

A

P-wave

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13
Q

What occurs during atrial systole?

A

Atria already almost full from passive filling driven by pressure gradient. Atria contract to ‘top-up’ the volume of blood in ventricle

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14
Q

What heart sound is atrial systole responsible for?

A

4th heart sound
Abnormal
Would normally be silent

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15
Q

What does an abnormal 4th heart sounds indicate?

A

congestive heart failure pulmonary embolism

tricuspid incompetence

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16
Q

What is the second phase of the cardiac cycle?

A

Isovolumetric contaction

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17
Q

What is isovolumetric contraction on an ECG?

A

QRS complex marks the start of ventricular depolarisation

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18
Q

What occurs during isovolumetric contraction?

A

This is the interval between AV valves (tricuspid & mitral) closing and semi-lunar valves (pulmonary & aortic) opening

Contraction of ventricles with no change in volume

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19
Q

What heart sound is isovolumetric contraction responsible for?

A

1st heart sound (‘lub’) due to closure of AV valves and associated vibrations

20
Q

What is the third phase of the cardiac cycle?

A

Rapid ejection

21
Q

What marks the start of rapid ejection?

A

Opening of the aortic & pulmonary valves

22
Q

What occurs during rapid ejection?

A

As ventricles contract pressure within them exceeds pressure in aorta and pulmonary arteries. Semilunar valves open, blood pumped out and the volumes of ventricles decrease.

23
Q

What is the heart sound for rapid ejection?

A

No heart sounds are heard for this phase

24
Q

What is the fourth phase of the cardiac cycle?

A

Reduced ejection

25
Q

What does reduced ejection mark?

A

End of systole

26
Q

What occurs during reduced ejection?

A

Reduced pressure gradient means aortic & pulmonary valves begin to close

Blood flow from ventricles decreases and ventricular volume decreases more slowly

As pressures in ventricles fall below that in arteries, blood begins to flow back causing semilunar valves to close

27
Q

What is the fifth stage of the cardiac cycle?

A

Isovolumetric relaxation

28
Q

What occurs during isovolumetric relaxation?

A

The aortic & pulmonary valves shut, but the AV valves remain closed until ventricular pressure drops below atrial pressure.

Atrial pressure continues to rise. Dichrotic notch (green line) caused by rebound pressure against aortic valve as distended aortic wall relaxes.

29
Q

What heart sound is isovolumetric relaxation responsible for?

A

2nd heart sound (‘dub’) due to closure of semilunar and associated vibrations

30
Q

What is the sixth phase of the cardiac cycle?

A

Reduced passive filling

31
Q

What can reduced passive filling also be known as?

A

Diastasis

32
Q

What occurs during reduced passive filling?

A

Ventricular volume fills more slowly

The ventricles are able to fill considerably without the contraction of the atria.

33
Q

What are the difference between the left and right sides of the heart?

A

the pressures in the right heart and pulmonary circulation are much lower (peak of systole – 25mmHg in pulmonary artery)
Left: 120mmHg

34
Q

What are the similarities between the left and right side of the heart?

A

The patterns of pressure changes in the right heart are essentially identical to those of the left

right ventricle ejects same volume of blood as left

35
Q

What determines the preload that stretches the resting ventricular muscle?

A

Blood filling the ventricles during diastole

36
Q

What represents afterload?

A

The blood pressure in the great vessels

aorta and pulmonary artery

37
Q

What does increased preload result in?

A

Increased stroke volume

Frank-Starling relationship

38
Q

What does increased afterload result in?

A

Decreased stroke volume

Decreased shortening

39
Q

What is cardiac output equal to?

A

Heart rate x Stroke volume

40
Q

What affects stroke volume?

A

Preload
Afterload
Contractility

41
Q

Define contractility?

A

Contractile capability (or strength of contraction) of the heart

42
Q

How can contractility be measured?

A

Ejection fraction

43
Q

What increases contractility?

A

Sympathetic stimulation
More calcium release
Increases gradient of pressure and volume relationship
Increased force

44
Q

What does hardening and narrowing of the aortic valve result in?

A

Reduces flow

Increases afterload

45
Q

What does acute blood loss result in?

A

Reduces venous return

Decreases preload

46
Q

What does exercise result in?

A

Venous return increases due to venoconstriction and skeletal muscle pump, and contractility is increased via sympathetic nervous system

Cardiology (16 decks)

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