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BRS 6: Cardiovascular And Respiratory Medicine > 6.5: Cardiac cycle > Flashcards

6.5: Cardiac cycle Flashcards

1
Q

Systole is

A

Contraction - ventricles generate pressure then eject blood into arteries

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2
Q

Diastole is

A

Relaxation - ventricles fill with blood

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3
Q

Each heart beat is split into two main phases

A

Diastole and systole

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4
Q

Diastole is split into how many phases

A

4 distinct phases

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5
Q

Systole is split into how many phases

A

3 distinct phases

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6
Q

7 stages of the cardiac cycle

A

Atrial systole (D)
Isovolumetric contraction (S)
Rapid ejection (S)
Slow ejection (S)
Isovolumetric relaxation (D)
Rapid passive filling (D)
Slow passive filling (D)

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7
Q

P wave on an ECG signifies

A

Start of atrial systole

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8
Q

In atrial systole

A

Atria are almost full from passive filling, driven by pressure gradient.
Atria contract to “top-up” volume of blood in ventricle

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9
Q

What 3 diseases can cause a 4th heart sound to arise (abnormal)

A

Congestive heart failure
Pulmonary embolism
Tricuspid incompetence

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10
Q

What does the QRS complex mark the start of

A

Ventricular depolarisation

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11
Q

During Isovolumetric contraction

A

[Contraction of ventricles with no change in volume (isometric)]
Interval between AV valves closing and semi-lunar valves opening

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12
Q

1st stage of cardiac cycle

A

Atrial systole

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13
Q

2nd stage of cardiac cycle

A

Isovolumetric contraction

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14
Q

Isovolumetric contraction produces

A

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

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15
Q

What marks the start of the rapid ejection phase

A

Opening of the aortic and pulmonary veins

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16
Q

During the rapid ejection phase

A

Ventricles contact, pressure within them exceeds pressure in aorta and pulmonary arteries
Semilunar valves open, blood is pumped out and volumes of ventricles decrease - isotonic contraction
(No heart sounds)

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17
Q

3rd phase of the cardiac cycle

A

Rapid ejection

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18
Q

4th phase of cardiac cycle

A

Slow ejection / reduced ejection

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19
Q

5th phase of cardiac cycle

A

Isovolumetric relaxation

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20
Q

6th phase of cardiac cycle

A

Rapid passive filling

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21
Q

7th phase of cardiac cycle

A

Slow passive filling

22
Q

Calculation for stroke volume

A

End diastolic volume - end systolic volume = stroke volume (mL)

23
Q

Calculation for ejection fraction (%)

A

100x (stroke volume / end diastolic volume ) = ejection fraction

24
Q

Reduced ejection marks

A

The end of systole

25
Q

During reduced ejection

A

Reduced pressure gradient means aortic and pulmonary valves being to close.
Blood flow from ventricles decreases and ventricular volume decreases more slowly
As pressure in ventricles fall below that in arteries, blood begins to flow back causing semilunar valves to close

26
Q

What produces the T wave on an ECG

A

Ventricular muscle cells repolarizing - during reduced ejection

27
Q

During Isovolumetric relaxation

A

Aortic and pulmonary valves shut,
AV valves remain closed until ventricular pressure drops below atrial pressure.
Atrial pressure continues to rise

28
Q

What causes the Dichrotic notch on an ECG

A

Rebound pressure as distended aortic wall relaxes - Isovolumetric relaxation

29
Q

What is the 2nd heart sound caused by

A

Closure of semi-lunar valves

30
Q

Rapid passive filling on and ECG is represented by

A

Isoelectric (flat) between cardiac cycles

31
Q

During rapid passive filling

A

Once AV valves open blood in the atria flows rapidly into ventricles

32
Q

3rd heart sound can be due to

A

Usually abnormal
May signify turbulent ventricular filling
Can be due to hypertension or mitral incompetence

33
Q

Reduced passive filling is also known as

A

Diastasis

34
Q

During reduced passive filling

A

Ventricular volume fills more slowly
Ventricles are able to fill considerably without the contraction of the atria

35
Q

What are the patterns of pressure changes like in the right heart compared to the left

A

Identical in the right heart as in the left

36
Q

Comparison of heart pressures quantitativley

A

Pressures in right heart and pulmonary circulation are much lower in the right heart but ejects same volume of blood as left

37
Q

Pressures in the systemic circuit

A

High pressure
120/80 mmHg

38
Q

Pressures in the pulmonary circuit

A

Low pressure
25/5 mmHg

39
Q

Preload is determined by

A

Volume of blood returning to the heart (blood filling ventricles during diastole , stretching resting ventricular muscle)

40
Q

Afterload is

A

Pressure heart has to work against

41
Q

What is afterload determined by

A

Diastolic blood pressure (BP in great vessels - aorta, pulmonary artery)

42
Q

What is preload

A

Stretch

43
Q

What do Changes in preload and afterload affect

A

Shape of the PV loop

44
Q

What does increased sympathetic stimulation result in

A

Increased cardiac myocyte [cAMP]
Allows delivery of more Ca2+ to myofilaments

45
Q

Delivery of more Ca2+ by increased sympathetic stimulation results in

A

Activation of sympathetic beta receptors by:
Circulating catecholamines from adrenal gland
Noradrenaline released from nerves

46
Q

What affects the width of the PV loop

A

Changes in preload

47
Q

What affects the height and left border of the PV loop

A

Changes in afterload
Upper left point follows the ESPVR

48
Q

What stimulation is present at rest

A

Parasympathetic

49
Q

What happens to the heart rate at rest

A

Slowing of SA node due to parasympathetic stimulation
From 110bpm to 70bpm

50
Q

How does the sympathetic stimulation increase SA node rate (2)

A

Hormonal : circulating adrenaline from adrenal gland
Neural : noradrenaline released from nerves

51
Q

What is the longest phase of the cardiac cycle

A

TBA…

BRS 6: Cardiovascular And Respiratory Medicine (12 decks)

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