Cardiac cycle Flashcards

1
Q

What is a Wiggers diagram?

A

Shows changes in pressure, volume, electrical activity, sound
during the cardiac cycle

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2
Q

How does a Wiggers diagram of the left side of the heart compare to that of the right side of the heart?

A

Very similar

except left side is at higher pressures

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3
Q

What are the phases of the cardiac cycle?

A

Systole

Diastole

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4
Q

What is systole?

A

Contraction and ejection of blood from ventricles

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5
Q

What is diastole?

A

Relaxation and filling of ventricles

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6
Q

What are the phases of systole?

A

Isovolumetric contraction
Rapid ejection
Reduced ejection

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7
Q

What are the phases of diastole?

A

Isovolumetric relaxation
Rapid filling
Reduced filling
Atrial contraction

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8
Q

What happens in atrial contraction?

A

P wave on ECG - atrial depolarisation

A wave in atrial pressure - atrial pressure increases

EDV in ventricular volume - ventricular volume increases to EDV

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9
Q

Atrial contraction accounts for what percentage of ventricular filling?

A

10%

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10
Q

What is EDV?

A

End diastolic volume

volume in left ventricle at end of diastole

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11
Q

What is the average EDV?

A

120ml

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12
Q

What happens in isovolumetric contraction?

A

QRS complex in ECG - ventricular depolarisation

Increase in ventricular pressure - ventricle contracting

S1 sound - closure of mitral valve (tricuspid valve too) as intraventricular pressure exceeds atrial pressure

C wave in atrial pressure - atrial pressure increases due to closure of mitral valve, slight inversion into atria

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13
Q

What is meant by isovolumetric in isovolumetric contraction/relaxation?

A

Both valves are closed

no change in volume of blood in left ventricle

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14
Q

What happens in rapid ejection?

A

Increase in ventricular pressure - ventricle contracting

Aortic valve opens - intraventricular pressure exceeds aortic pressure

Increase in aortic pressure - filling with blood from ventricle

Decrease in ventricular volume - ventricle ejecting blood into aorta

X descent in atrial pressure - atrial pressure decreases as base of atria pulled down

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15
Q

What happens in reduced ejection?

A

T wave on ECG - ventricular repolarisation

Decrease in ventricular pressure - ventricle relaxing

Decrease in aortic pressure - less blood entering it from ventricle, blood begins to leave it

V wave in atrial pressure - atrial pressure increases as it fills with blood from venous return

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16
Q

What hapens in isovolumetric relaxation?

A

Decrease in ventricular pressure - ventricle relaxing

S2 sound - aortic valve closure as aortic pressure exceeds intraventricular pressure, backflow of blood, valve closes

Dicrotic notch in aortic pressure - increase in aortic pressure, walls of aorta pulled inwards as valve closes

ESV in ventricular volume - end systolic volume, volume of blood in ventricles at end of systole

17
Q

What is the average ESV?

A

40ml

18
Q

What happens in rapid filling?

A

Mitral valve opens - atrial pressure exceeds intraventricular pressure

Y descent in atrial pressure - atrial pressure decreases as it empties of blood

Increase in ventricular volume - increases as ventricle fills with blood from atria

S3 sound - ventricular filling

19
Q

How do the ventricles fill with blood from the atria in rapid filling?

A

Passively

20
Q

When is the S3 sound normal? When is it a sign of pathology?

A

Normal in children

Sign of pathology in adults

21
Q

What happens in reduced filling?

A

Increase in ventricular volume - slowly increases called diastasis, reach 90% of EDV

22
Q

What is the pressure in the left atrium?

A

8-10mmHg

23
Q

What is the pressure in the LV?

A

120/10mmHg

24
Q

What is the pressure in the aorta?

A

120/80mmHg

25
Q

What is the pressure in the right atrium?

A

0-4mmHg

26
Q

What is the pressure in the pulmonary artery?

A

25/10mmHg

27
Q

What is the pressure in the RV?

A

25/4mmHg

28
Q

How do the pressures of the systemic and pulmonary circulations compare to each other?

A

Systemic circulation at high pressure

Pulmonary circulation at low pressure

29
Q

If the cardiac cycle is 0.9s long, how long is systole? How long is diastole?

A

Systole = 0.35s

Diastole = 0.55s

30
Q

A change in heart rate is accommodated by change in duration of systole or diastole or both?

A

Diastole