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CVS > Mechanics 2 > Flashcards

Mechanics 2 Flashcards

1
Q

What are the in vivo correlates of Frank Starling relationship?

A

force –> pressure

length –> volume

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2
Q

How are PV loops used clinically?

A

show contractility

give idea of filling pressure of ventricles

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3
Q

What does the cardiac cycle consist of?

A

diastole
2/3 ventricular relaxation - 4 subphases

systole
1/3 ventricular contraction - 2 subphases

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4
Q

What is isovolumetric ventricular contraction?

A

pressure builds up in ventricles in early systole until pressure exceeds pressure of afterload

increase tension, no change in volume

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5
Q

What is EDV?

A

volume of blood in ventricle at end of ventricular filling just before contraction

approx 130ml
ESV = 60ml, 40ml added in atrial diastole, 30ml added in atrial systole

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6
Q

What is ESV?

A

volume left in ventricle at end of contraction

approx 60ml

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7
Q

What is stroke volume?

A

volume of blood ejected by ventricular contraction
approx 70ml
SV = EDV - ESV
= 130-60

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8
Q

What is ejection fraction %?

A

proportion of EDV pumped out of heart

= SV/EDV x 100%

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9
Q

What is normal heart rate?

A

72bpm or 0.8s per beat of heart

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10
Q

What is cardiac output?

A

HR x SV

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11
Q

What is MAP?

A

DBP + 1/3PP

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12
Q

What is pulse pressure?

A

DBP - SBP

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13
Q

What affects stroke volume?

A

preload (venous return)
afterload (arterial pressure)
contractility (influenced by autonomic NS and adrenaline - sympathetic branch)

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14
Q

What is contractility?

A

strength of contraction of heart
measured by ejection fraction
increased by sympathetic stimulation (exercise)

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15
Q

What is the last stage of diastole?

A

Atrial systole
P wave
atrial depolarisation
initiated by pacemaker potential emanating from the SAN

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16
Q

Describe the process of atrial systole?

A

final phase of diastole
atria contract to fill the ventricles (EDV)
AV valves open
atrial pressure increases

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17
Q

Why are atria almost full before atrial systole?

A

passive filling of atria driven by pressure gradient

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18
Q

What happens as the atria contract?

A

jugular pulse as blood is pushes back up the jugular vein

19
Q

What can be heard abnormally during atrial systole? What are the causes?

A 
S4 heart sound - lub lub dub
due to valve incompetency (bad shutting)
1. pulmonary embolism
2. congestive heart failure
3. tricuspid incompetence
20
Q

Step 1 of systole?

A

isovolumic contraction
QRS is the start - ventricular depolarisation
AV valves shut

21
Q

Describe isovolumic contraction?

A

GOAL: to reach pressure that exceeds arterial pressure

  • contraction of ventricles with no change in volume
  • no change in fibre length
  • SI sound heart ‘lub’ which is the AV valve shutting
22
Q

Step 2 of systole?

A

rapid ejection

start marked by opening of aortic/pulmonary valves

23
Q

Describe rapid ejection?

A

ventricles contract isotonically
ventricular pressure rapidly rises to exceed aortic pressure (afterload) so SL valves open
ventricular volume decreases
no ECG or heart sounds

24
Q

What is the a wave?

A

increase atrial pressure due to passive filling

25
Q

What is the c wave?

A

pushing of tricuspid valve into atrium which increases pressure in the jugular vein due to ventricular contraction

26
Q

Step 3 of systole?

A

Reduced ejection
Marks the end of systole
T wave - ventricular repolarisation (positive to negative potential)

27
Q

Describe reduced ejection?

A

Aortic and pulmonary valves begin to close - pressure gradient causes backflow from arteries
Blood flow from ventricles decreases because blood has left ventricles so ventricular volume and pressure decrease more slowly

28
Q

Stage 1 of diastole?

A

isovolumic relaxation
aortic and pulmonary valves close
S2 heard when valves close - ‘dub’

29
Q

What is the dichrotic notch?

A

small sharp increase in aortic pressure due to rebound pressure against aortic valve as distended aortic wall relaxes

30
Q

Describe isovolumic relaxation

A

atria are filled with blood
AV valve shuts
atrial pressure increases

31
Q

What is the v wave?

A

second jugular pulse

blood pushes back on tricuspid valve

32
Q

Stage 2 of diastole?

A

Rapid/passive ventricular filling

AV valves open

33
Q

Describe rapid/passive ventricular filling

A 
atrial pressure falls as ventricular volume increases 
passive 
during flat (isoelectric) ECG between cycles
34
Q

What might be heart during rapid/passive ventricular filling?

A

abnormal S3
due to turbulent ventricular filling
= ventricular gallop lub dub dub
Caused by severe hypertension/mitral incompetence

35
Q

Stage 3 of diastole?

A

Reduced ventricular filling

= diastasis

36
Q

Describe reduced ventricular filling?

A

ventricular volume increases more slowly

aortic pressure gradually decreasing

37
Q

What defines the preload?

A

how much ventricles fill

the stretch in turn defined contractility on-top of the heart own intrinsic control of contraction

38
Q

Where is there shorter insulation?

A

L than R

39
Q

Why must the ventricular septum depolarise first?

A

to allow heart to have an anchor to contract around and eject blood

40
Q

What is normal systemic BP?

A

120/80

41
Q

What is normal pulmonary BP?

A

25/5

42
Q

What is pulmonary wedge pressure?

A

measure pressure in pulmonary artery (RHS) to measure the preload on the left as sides are linked by the pulmonary circuit

an increase in PAWP is indicative of LEFT heart failure

43
Q

What does pulmonary circuit pressure do?

A

changes

44
Q

Describe extrinsic heart stimulation

A

PNS at rest slows HR from SAN from 110 to 70 bpm
SNS increases HR by
- hormonal control (adrenaline from adrenal gland)
- neural control (noradrenaline released from nerves)

CVS (16 decks)

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