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Contractility & Cardiac Output Flashcards

(36 cards)

1
Q

What is preload?

A

aka left ventricular end diastolic volume

-amount of blood ready to be pumped

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2
Q

What is preload directly related to?

A

-fiber length @ end of diastole

–> as ventricle fills with more blood, fibers get longer

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3
Q

How does venous return affect preload?

A

> venous return -> > preload

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4
Q

What is the tension relationship & preload?

A

cardiac output = venous return at a steady state

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5
Q

What is frank starling relat?

A

-volume of blood ejected by ventricle depends od the volume present in the ventricle at end of diastole

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6
Q

What is after load?

A

(for LV) the aortic pressure aka the force opposing contraction

–> pressure required to eject blood by opening the aortic valve

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7
Q

What is the relationship b/w velocity of shorting and after load?

A

-velocity of shortening DECREASES as after load INCREASES

greatest if after load = 0

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8
Q

What is stroke volume and how do you calculate for it?

A

volume of blood ejected by ventricle with each beat

SV = EDV - ESV (~70mL)

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9
Q

What is ejection fraction and how do you calculate it?

What does it measure?

A
  • fraction of EDV ejected in each stroke volume
  • measures efficiency and contractility
  • EF% = SV / EDV (~55%)
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10
Q

What physiological state would cause the ejection fraction to decrease?

A

heart failure

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11
Q

What is cardiac output and how to you calculate it?

A

-total volume of blood ejected by ventricle per minute

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12
Q

What are the two coupling factors that contribute to cardiac output?

A
  • preload
  • afterload

both relate to contractility

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13
Q

What happens to contractility as you increase preload?

A

-increase contractility and increase CO

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14
Q

What happens to CO as you increase after load?

A

decrease in CO

heart must overcome by increasing contractility or HR

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15
Q

What is the positive staircase effect?

A

an auto regulation method by which increased HR increases contractility (via more Ca2+ in cell and into SR)

aka positive chronotropic effect creates a positive inotropic effect

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16
Q

How does sympathetic input affect cardiac output?

activation of what which does what?

A
    • iontropic effect via B-AR activation

- phosphorylation of sarcolemma Ca2+ channels, phospholamban (stimulatory), and troponin 1 (inhibititory)

17
Q

How does parasympathetic input affect cardiac output?

A
  • (-) iontropic effect via muscarinic receptor activation
  • decrease inward Ca2+ current during plateau
  • ACh increased outward flow of K+ current via K+-(-)ACh channels
18
Q

What does administering isoproterenol (B-AR agonist ) do ?

A

increases HR and contractility

treats bradycardia

19
Q

What factors can increase preload?

A
  • increased venous return

- high blood volume

20
Q

What factors can increase after load?

A
  • aortic stenosis

- hypertension

21
Q

What factor can increase contractility directly?

A

adrenergic stimulation

22
Q

What is volume work and how do you calculate it?

A

-cardiac output (SV x HR)

23
Q

What is pressure work?

A

aortic pressure

24
Q

How do you calculate minute work?

A

CO x aortic pressure (SV x HR x aortic pressure)

25
How do you calculate stroke work?
SV x aortic pressure (LV) | -the area within the volume pressure loop?
26
What is the difference b/w volume work (cardiac output) and stroke work?
Stroke work takes into account the pressure in the aorta; volume work factors in HR
27
What is the Fick Principle? (myocardial O2 consumption)
States that he largest % of O2 consumption is pressure work rather than CO (SV x HR) -LV must work proportionally harder than RV due to systemic pressure > aortic pressure
28
What further accents increase LV pressure work ?
- aortic stenosis - systemic hypertension aka the LV myocytes are using more oxygen to accomplish their tasks to overcome a higher after load pressure and thus more "work"
29
How do you calculate Os consumption ?
O2 consumption = CO x ( [O2]pulm v. - (CO x [O2]pulm a.) ) CO = O2 consumption / ( [O2]pulm v. -[O2]pulm a. )
30
What 3 factors play major roles on the cardiac function curve?
- venous return - RA pressure - EDV and end diastolic fiber length
31
What is the relationship of venous return and CO at equilibrium?
- venous return = CO | - aka volume of blood as cardiac output ejected by ventricle matches the volume it reaches in venous return
32
What happens to the RA pressure and venous return when you increase iontropy vs decrease?
increase = RA pressure decreases ; CO/venous return increases Decreases = RA pressure increases ; Venous return decreases
33
What occurs to RA pressure and venous return when you increase TPR vs decrease TPR?
increase : RA pressure remains constant ; venous return decreases decrease : RA pressure remain constant ; Venous return increases
34
What occurs to RA pressure and venous return when you increase blood volume vs decrease blood volume?
increase : RA pressure increases ; venous return increases Decrease : RA pressure decreases; venous return decreases
35
What happens during cardiac failure?
- decrease iontropy (contractility) - decrease vascular compliance - increase BP - increase SVR/TPR
36
What happens to the pressure in the RA and venous return in cardiac failure?
- RA pressure increases - cardiac output decreases -increase in volume, decrease contractility of ventricle , and increase TPR