CVS 3 - Mechanical properties of the heart 2 Flashcards

1
Q

What are the two main phases of the heart beat?

A

Systole - 2 subparts

Diastole - 4 subparts

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2
Q

State the phases of the cardiac cycle

A

(Diastole)
1. Slow filling (of atria and ventricules, AV valves opened)
2. Atrial systole
(Systole)
3. Isovolumetric ventricular contraction -
(unchanged volume, all valves closed isometric contraction)
4. Ventricular ejection - semilunar open
(Diastole) - rapid ejection + reduced ejection
5. Isovolumetric ventricular relaxation
6. Rapid filling then back to reduced filling (step 1)

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3
Q

What happens during slow ventricular filling?

A

Phase: Atria and ventricles relaxed, blood filling ventricles slowly
Valves: AV open, semilunar closed

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4
Q

What happens during atrial systole?

A

Phase: Atria contract, top off ventricles with blood
Valves: AV open, semilunar closed
P wave: atrial depolarisation

S4: Abnormal heart sound

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5
Q

What happens during isovolumetric ventricular contraction?

A

Phase: Contraction of ventricles with no change in volume
Valves: AV closes as pressure in ventricles exceeds atria
QRS: Ventricular depolarisation
S1: “lub” from the closure of the AV valves

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6
Q

What happens during ventricular ejection (aka ‘rapid ejection’ + ‘reduced ejection’)?

A

Rapid ejection:
Phase: Ventricles contract –> pressure within exceeds aortic and pulmonary artery
Valves: Semilunar open –> blood leaves heart
RV contraction pushes tricuspid valve into atrium –> creates wave in jugular vein – “C” wave
The ventricular pressure exceeds the aortic and pulmonary pressures so the aortic and pulmonary valves open and blood rapidly flows out into the aorta and pulmonary artery.

Then reduced ejection:
Phase: Blood flow from ventricles decreases
Valves: SL BEGIN to close because blood starting to flow back from arteries due to lower ventricular pressure
T wave: Ventricular repolarisation
Marks the end of systole. Ventricular pressure begins to fall
T wave on the ECG due to the repolarisation of the ventricles. There are NO heart sounds because none of the valves are shutting.

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7
Q

What happens during isovolumetric ventricular relaxation?

A

Phase: Atria filling with blood
Valves: SL shut, AV shut (Shutting of atrial valve creates dichrotic notch in atrial reading)
S2: “dub” from SL valves closing

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8
Q

What happens during rapid ventricular filling?

A

Phase: Ventricles filling
Valves: AV valve open
S3: Abnormal, due to mitral incompetence

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9
Q

What is ejection fraction?

A

SV/EDV - the proportion of the blood in the heart that is pumped out in one contraction

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10
Q

What ECG change is seen in atrial systole?

A

P wave - atrial depolarisation

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11
Q

What abnormal heart sound could be heard during atrial systole and what could it be a result of?

A

S4 - this could be due to tricuspid incompetence, pulmonary embolism or congestive heart failure

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12
Q

How does atrial pressure change during atrial contraction?

A

Atrial pressure shows a small increase - a wave

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13
Q

Describe the pressure and volume changes that take place during isovolumic contraction.

A

The valves are all closed so there is no change in volume but the pressure increases dramatically.

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14
Q

What heart sound will be heard during isovolumic contraction?

A

S1 - closing of the atrioventricular valves

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15
Q

What ECG change is seen during isovolumic contraction?

A

QRS complex - ventricular depolarisation

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16
Q

Describe the electrical activity and heart sound heard during rapid ejection.

A

There is no electrical activity - isoelectric line on ECG. No heart sounds are heard.
Depolarisation of heart happens before this

17
Q

What is the dichrotic notch and when does it occur?

A

The dichrotic notch is caused by the elastic recoil of the aorta causing a small rise in aortic pressure once ventricular contraction has ended.

18
Q

What changes in pressure occur during isovolumic relaxation?

A

The atrial pressure increases due to the filling against closed valves - v wave. Volume of the ventricles does not change. (the AV and SL valves are closed)

19
Q

What heart sound can be heard during isovolumic relaxation?

A

S2 - this is due to the shutting of the aortic and pulmonary valves

20
Q

What changes in volume and pressure take place during rapid ventricular filling?

A

There is a gradual increase in ventricular volume but ventricular pressure remains about the same. Atrial pressure decreases. This is just before reduced filling then atrial systole

21
Q

What abnormal heart sound can be heard during rapid ventricular filling and what could it be a result of?

A

S3 usually abnormal and can signify turbulent ventricular filling
Can be due to severe HT or mitral incompetence

22
Q

What diagram can show all this information?

A

Wiggers diagram

23
Q

What is the normal pressure in the pulmonary circulation?

A

25/5 mmHg

24
Q

What do points 1-4 on the pressure-volume loop indicate?

A

1 - EDV
2 - Aortic pressure encountered –> pressure has been build up but same volume
3 - ESV –> pressure is the same, lower volume
4 - same volume (low) and smaller pressure
Then heart fills again but same pressure and no contraction so this is EDV then contracts blabla pressure increases but same volume (2) etc.
In clinic this is used to see how heart is working, in transplants for example.

25
Q

Which feature of the pressure-volume loop indicates stroke volume?

A

The length between point 3 and 2 ie between just before contraction so max volume and just after systole - ESV so volume that stayed in ventricles.
pressure is the same and volume has been ejected so the difference in volume in the heart is the volume ejected so stroke volume

26
Q

Which points on the pressure-volume loop indicate preload and afterload?

A

Afterload is after point 2 as it is when the aortic pressure is encountered
Preload is point 1 as point 1 is EDV

27
Q

What effect do preload and afterload have on pressure-volume loops?

A

If preload increases, diagram becomes larger on the right –> because SV increases
If afterload increases, diagram becomes thinner on the left –> because SV decreases (point 1 remains the same as EDV is the same)

28
Q

What effect do afterload and preload have on stroke volume?

A

Afterload decreases SV as the more afterload there is, the greater the pressure you have to work against
Preload increases SV
This will have an effect on CO

29
Q

What is contractility? What is its effect on the pressure volume loop?

A

It is the contractile capability of the heart.
Measure of contractility is ejection fraction.
Contractility is increased during sympathetic stimulation so during exercise.
This will make the pressure volume loop wider ! (also the fact that EDV changes with exercise because of changes in peripheral circulation - vasoconstriction - venous return is bigger)