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CPR Midterm > CPR Contractility & Cardiac Output > Flashcards

CPR Contractility & Cardiac Output Flashcards

1
Q

What is cardiac output dependent on?

A

Heart rate
Contractility
Preload
Afterload

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2
Q

How do cardiac glycosides work?

A

used to treat heart failure by

inhibition of K+ binding on Na/K ATPase
increases Na+ conc
decreases Ca2+ efflux thru Ca2+/Na+ exhanger
increases intracell Ca2+
positive inotropic effect
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3
Q

How do you calculate cardiac output?

A

CO=HR x SV

SV relates to myocardial contractility

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4
Q

What is left ventricular end-diastolic volume?

A

amount of blood ready to be pumped

wall tension in LV just before contraction is initiated

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5
Q

What is the Frank-Starling relationship?

A

volume of blood ejected by ventricle depends on volume present in ventricle @ end of diastole

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6
Q

How do CO & venous return relate?

A

CO=venous rate (steady state)

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7
Q

What is afterload?

A

for LV, is related to aortic pressure

the force opposing contraction/pressure required to eject blood from LV

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8
Q

Preload v Afterload w/ in cardiac cycle

A

Preload=LV end-diastolic volume (fiber length from where muscle contracts)

Afterload=aortic pressure (what is needed to open aortic valve)

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9
Q

What is stroke volume?

A

volume of blood ejected by ventricle w/ each beat

SV=EDV - ESV
Usually about 70ml

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10
Q

What is ejection fraction?

A

fraction of EDV ejected in each stroke volume
(measure of efficiency and contractility)

EF = SV/EDV, approx 55%

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11
Q

What is cardiac output?

A

total volume of blood ejected by ventricle per min

CO (Q) = SV x HR

usually is 5 L/min

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12
Q

What happens to CO if preload increases?

A

increases CO & contractility in a healthy heart

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13
Q

What happens to CO if afterload increases?

A

decrease CO (must increase contractility or increase HR)

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14
Q

What is the effect of HR on contractility?

A

increased HR increases contractility (more Ca2+ enters cells & taken up into SR)

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15
Q

What is the effect of sympathetic stimulation on CO?

A

positive ionotropic effect

inhibits troponin I & stimulates phospholamban & sarcolemma Ca2+ channels

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16
Q

What is the effect of parasympathetic stimulation on CO?

A

negative ionotropic effect in ATRIA only (no influence on ventricular myocytes)

activation of muscarinic receptor decreases inward Ca+ current & increase K+ efflux

17
Q

What does phase 1 to 2 on vent pressure-volume loop represent?

A

isovolumetric contraction

18
Q

What does phase 2 to 3 on pressure volume loop represent?

A

ventricular ejection

19
Q

What does phase 3 to 4 on pressure volume loop represent?

A

isovolumetric relaxation

20
Q

What does phase 4 to 1 on pressure volume loop represent?

A

ventricular filling

21
Q

What compensation occurs with increased preload?

A

more venous return, more blood volume

increased SV

22
Q

What compensation occurs with increased afterload?

A

aortic stenosis, hypertension

greater pressure needed w/ reduced SV & EF%

23
Q

What compensation occurs with increased contractility?

A

adrenergic stimulation

increased SV & EF%

less blood left in heart

24
Q

What is pressure work?

A

aortic pressure

25
Q

What is minute work?

A

CO x aortic pressure

26
Q

What is stroke work?

A

performed by LV (area w/ in pressure-volume loop)

stroke volume x aortic pressure

27
Q

What is the Fick Principle?

A

describes O2 consumption

O2 consumption= CO x (O2 in pulmonary vein - (CO)(O2 in pulmonary artery))

28
Q

What does the cardiac function curve describe?

A

relationship between CO & venous return

as venous return increases, RA pressure increases & EDV & end-diastolic fiber length increases

29
Q

What does equilibrium on cardiac function curve indicate?

A

CO = venous return (will vary depending on state of CV system)

30
Q

What is a vascular function curve?

A

mean circulatory filling pressure

when there is no CO & depends entirely on vascular compliance & blood volume

31
Q

Cardiac Failure

A

decreased ionotropy
decreased vascular compliance
increased blood volume
increased SVR/TPR

CPR Midterm (20 decks)

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