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Cardiovascular > Cardiac cycle > Flashcards

Cardiac cycle Flashcards

1
Q

What is dystole?

A

Lasts approximately 2/3 of each beat

Ventricular relaxation
The ventricles fill with blood ( from atriums into ventricles on both right and left )

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2
Q

What is systole?

A

Lasts approximately 1/3 of each beat

Ventricular contraction

Ventricles generate pressure then eject blood into the arteries ( aorta and pulmonary )

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3
Q

How many phases is diastole split into?

A

4

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4
Q

How many phases is systole split into?

A

3

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5
Q

How to calculate stroke volume?

A

end diastolic Volume - End systolic volume

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6
Q

What are the phases on Diastole?

A

Isovolumetric relaxation –> rapid passive filling –> slow passive filling –> atrial systole

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7
Q

What is the end systolic volume?

A

Amount of blood in heart after contraction is completed - residual volume

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8
Q

What is end diastolic volume?

A

The maximum volume of blood in the heart just before the ventricles start to contract. So at maximum relaxation

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9
Q

What are the phases of systole?

A

Isovolumetric contraction –> rapid ejection –> slow ejection

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10
Q

How to calculate Ejection fraction?

A

( Stroke volume / End-diastolic volume ) x 100

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11
Q

Normal range of Ejection fraction?

A

52-72 %

  • clinical indicator of heart function
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12
Q

What is the Mitral valve?

A

Bicuspid valve - left side of heart between atrium and ventricle

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13
Q

What on the ECG signifies the start of atrial systole?

A

P-wave

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14
Q

Why do the atria contract?

A

To ‘top up’ the volume of blood in the ventricle so there is more than what is passively filled.

  • Atrial contribution to ventricular filling varies inversely with the duration of diastolic period. e.g. when diastolic interval is small the ventricular filling is aided by atrial contraction
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15
Q

What may a 4th heart sound be?

A

abnormal = congestive heart failure, pulmonary embolism, valve incompetence. ( heard during atrial systole )

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16
Q

What on the ECG signifies the start of ventricular depolarisation?

A

QRS complex

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17
Q

What is the isovolumetric contraction interval?

A

Interval between AV valves closing and semi-lunar opening

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18
Q

What is the contraction of ventricles with no change of volume?

A

Isovolumetric contraction

Because both valves have closed

But pressure of ventricles increase to the extent of aortic pressure

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19
Q

What is the 1st heart sound attributed to?

A

‘lub’

closure of AV valves and their vibrations

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20
Q

What marks the start of rapid ejection?

A

Opening of aortic and pulmonary valves.

= ejection begins when intraventricular pressure exceed aorta and pulmonary arteries. Causing valves to open

  • as blood is pumped out ventricular volume falls
21
Q

Is there a heart sound for rapid ejection?

A

No - valves opening doesn’t cause sound

22
Q

When is maximum blood velocity reached in the ejection phase

A

Very early on

23
Q

What does reduced ejection represent?

A

The end of the systole, T wave on the ECG = ventricular repolarisation occuring

24
Q

What does the ventricular repolarisation do?

A

Decline in ventricular active tension and pressure. So rate of ejection and ventricular emptying falls.

As this falls aortic and pulmonary valves close. and blood flow slows.

25
Q

What causes the semi-lunar valves to close

A

As pressure in ventricles falls below arterial pressure, blood begins t flow back closing the valves.

26
Q

What causes the second heart sound?

A

‘dub’

closure of semilunar valves

27
Q

What happens to the AV valves when the aortic and pulmonary valves shut?

A

( isovolumetric relaxation )

Remain closed until ventricular pressure drops below atrial pressure * volume does not change

28
Q

What is the dichrotic notch?

A

Caused by rebound pressure against aortic valve as distended aortal wall relaxes, increasing aortic pressure for a few msecs before lowering.

  • notice on graph
29
Q

What on the ECG signifies the rapid passive filling?

A

No electrical activity : flat area after T wave

30
Q

What occurs during rapid passive filling?

A

AV valves open and blood flows from atrium to ventricles

31
Q

What may a 3rd heart sound be?

A

usually abnormal and may signify turbulent ventricular filling

Can be due to severe hypertension or mitral incompetence

32
Q

What is Reduced passive filling?

A

Also known as diastasis

Ventricular volume fills more slowly. To a considerable amount before atrial contraction.

  • End of diastole
33
Q

The patterns of pressure changes in the right heart are ( x ) to those of the left

A

Identical

34
Q

The pressure in the right heart and pulmonary circulation are ( x ) than left

A

Much lower

  • despite lower pressure right ventricles ejects same volume of blood as left
35
Q

What does measuring pulmonary capillary wedge pressure give a clinical measurement of?

A

Left atrial pressure

  • Gives an idea of left ventrical failure and mitral valve stenosis. These are due to increase in left atrial pressure. This tends to lead to increased pulmonary oedema
36
Q

Why cannot we put a catheter in the left atrium to measure its pressure?

A

Although left ventricular pressure can be directly measured by placing a catheter within the left ventricle, it is not feasible to advance this catheter back into the left atrium.

37
Q

Referring to pressure volume loops; what happens when aortic pressure is encountered?

A

Left ventricular volume decreases and this is represented by the top curve towards end-systolic volume

38
Q

Referring to pressure loops, what does a larger preload do?

A

More blood moved into the L ventricle so more stretch occurs. And pressure increases ( larger Y axis value ) towards afterload.

39
Q

The blood pressure in the aorta represent the preload or afterload?

A

Afterload

40
Q

Affects of increased afterload?

A

less shortening of muscle fibres and so less able to expel blood from ventricles.

When afterload increases, there is an increase in end-systolic volume and a decrease in stroke volume.

Because a greater pressure is required to open the aortic valve.

  • slide 21
41
Q

What is the ESPVR?

A

End systolic PV line.

maximal pressure that can be developed by the ventricle at any given volume

42
Q

Increases in preload result in what change in stroke volume?

A

Increases ( Frank-starling relationship )

Venous return increase = left ventricular volume increase

43
Q

How to calculate cardiac output?

A

Heart rate x Stroke volume

Stroke volume affected by preload, afterload and contractility.

44
Q

What is Contractility?

A

strength of contraction of the heart

Increased by: Sympathetic stimulation

Extrinsic mechanism: Changes Ca2+ delivery to myofilaments

45
Q

Cardiac contractility affects ( x ) of the Frank starling relationship?

A

Steepness

Can produce a ‘family’ of ESPVR lines

46
Q

As contractility increases, ESPVR lines?

A

Increase steepness

Generates more force due to more calcium to myofilaments and vice versa

47
Q

During exercise, an (a) in end systolic volume and (b) in end diastolic volume leads to a (c) stroke volume

A

a - decrease
b - increase
c - greater

48
Q

What can happen to the end diastolic volume is heart rate is increased a lot?

A

Can lower it because less time is spent filling during diastole

Cardiovascular (7 decks)

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