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Cardiopulmonary Exam 2 > Cardiac Output and Contractility > Flashcards

Cardiac Output and Contractility Flashcards

1
Q
  • What is the effect of a positive inotropic agent?
A

Increase in contractility

  • Increase in EDV
  • Increase in CO
  • Increase in SV
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2
Q
  • What is the effect of a positive chonotropic agent?
A
  • Increase in HR
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3
Q
  • What is the effect of a negative inotropic agent?
A
  • Decrease contractility
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4
Q
  • What is the effect of a negative chonotropic agent?
A
  • Decrease HR
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5
Q
  • What is preload? (General sense)
A
  • End Diastolic Volume
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6
Q
  • What is preload in a more detailed sense?
A
  • Amount of wall tension in RV or LV just before contraction is initiated
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7
Q
  • What is afterload (in a general sense)?
A
  • Aortic diastolic pressure
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8
Q
  • What is afterload in a more detailed sense?
A
  • The amount of diastolic pressure in the aorta/pulmonary arteries that must be exceeded for semilunar valves to open
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9
Q
  • How are afterload and velocity related?
A
  • They are inversely related
  • Increase in afterload leads to a decrease in velocity of contraction/shortening of muscle fibers
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10
Q
  • How do you calculate stroke volume ?
A
  • SV=EDV-ESV
  • Note that in normal conditions, this is approx 70 mL
  • Represents volume of blood ejected by ventricle with each beat
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11
Q
  • How do you calculate ejection fraction?
A
  • EF%=SV/EDV
  • Usually around 55%
  • Represents the fraction of EDV that is ejected in each stroke volume
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12
Q
  • How do you calculate cardiac output?
A
  • CO=HR x SV
  • Volume of blood ejected by the ventricle per minute
  • Normal=5 L/min
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13
Q
  • What does the Frank Starling relationship tell us?
A
  • The volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole (EDV)
  • Note that EDV relates to venous return (more venous return, larger EDV)
  • In a steady state CO=venous return
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14
Q
  • Will a chonotropic effect have an inotropic effect?
A
  • Yes
  • Positive chonotropic effect will have positive effect on inotropy and vice versa
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15
Q

What is represented by points 1-2 in the following pressure volume curve?

A
  • Isovolumetric contraction
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16
Q
  • What is represented by points 2-3 in the pressure volume loop?
A
  • Ejection of blood
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17
Q
  • What is represented from points 3-4 in the pressure volume loop?
A
  • Isometric relaxation
18
Q
  • What is represented by points 4-1 in the pressure volume loop?
A
  • Ventricular filling
19
Q
  • Which point on the curve represents preload?
A
  • 1
  • Remember preload=EDV
20
Q
  • Which point on the loop represents afterload?
A
  • 2
  • Remember that afterload is the aortic pressure that must be exceeded in order for the aortic valve to open and blood to be ejected from the ventricle
21
Q
  • On which points of the loop are the AV valves opening and closing?
  • On which points of the loop are the semilunar valves opening and closing?
A
  • AV valves open during 4
  • AV valves close during 1
  • Semilunar valves open at 2
  • Semilunar valves close during 3
22
Q
  • What are the effects of increased pre-load on the pressure volume loop?
A
  • Increase in EDV
  • Afterload and contractility remain constant
  • Increased stroke volume
23
Q
  • What are the effects of increased afterload on the pressure volume loop?
A
  • Greater pressure in aorta
  • Reduced SV
  • Reduced EF%
24
Q
  • What are the effects of increased contractility on pressure volume loop?
A
  • Increased SV
  • Increased aortic pressure
  • Decreased ESV
25
Q
  • What type of effect does sympathetic stimulation have on CO?
  • Via what receptors does this act?
  • Via what NTX does this act?
  • What are the biochemical effects that occur as a result of sympathetic stimulation?
A
  • Positive inotropic effect
  • Beta 1 adrenergic receptors
  • NE
  • Phosphorylation of sarcolemma Ca2+ channels (leads to increased intracellular Ca2+ concentrations)
  • Phosphorylation of phospholamban (increased sequestering of Ca2+ in the SR; important for subsequent contractions)
  • Phosphorylation of Troponin I (Inhibits troponin i so that troponin c can bind to Ca2+ and help enable cross bridge formation)
26
Q
  • What type of effect does the parasympathetic nervous system have on cardiac output?
  • Through which receptor does it work?
  • What biochemical events occur as a result?
A
  • Negative inotropic effect in ATRIA ONLY
  • Muscarinic receptor activation
    • ​Decreases inward Ca2+ current during plateau
    • AcH increases outward K+ current via K+-ACh channel (hyperpolarizes membrane)
27
Q
  • How does increasing HR affect contractility?
A
  • Positive chonotropic effect increases HR and increased HR increases contractility (positive inotropic effect)
  • Positive staircase effect (Bowditch staircase)
    • ​More Ca2+ enters into cell and taken up into SR
  • Postextrasystolic potentiation (arrythmia, extra beat)
28
Q
  • What is volume work equivalent to?
  • What is pressure work equal to?
  • Which is greater?
A
  • Cardiac output
  • Aortic pressure
  • Pressure work
29
Q
  • What is minute work?
A

Minute work=CO x aortic pressure (pressure work)

30
Q
  • What is stroke work?
A
  • Performed by the LV
  • Stroke Work=SV X aortic pressure
  • Represents the area within the pressure volume loop
31
Q
  • What is the Fick principle?
A
  • Cardiac output=O2 consumption/([O2]pulmonary vein-[O2]pulmonary artery)
32
Q
  • What is the relationship between CO and venous return at a steady state?
A
  • At a steady state, the volume of blood ejected by Lv (CO)=venous return
33
Q
  • Changing what factor will shift which part of the cardiac curve ONLY?
A

Inotropy

34
Q
  • Changes in what parameter will change the vascular function curve only?
A
  • Changes in blood volume
35
Q
  • What parameter affects both Cardiac and Vascular function curves?
A

TPR

36
Q

What is represented by the blue dot in the following figure?

A

Equilibrium-where CO=venous return

37
Q

What is represented by the arrows in the following diagram?

A
  • 1st arrow=equilibrium where CO=venous return
  • 2nd arrow=Mean systemic pressure; proportional to blood volume and preload**
38
Q
  • What parameter is causing the changes in the cardiac function curve?
A
  • Left represents a positive inotropic effect (increased inotropy, increased HR, increased afterload)
  • Left represents a negative inotropic effect (decreased inotropy, decreaed heart rarte, increased afterload)
39
Q
  • Changing what parameter has caused the shifts in the following figures?
A
  • Right
    • Increasing blood volume
    • Decreasing systemic vascular resistance (SVR)
    • Decreasing mean circulatory filling pressure/mean systemic pressure
  • Left
    • Decreasing blood volume
    • Increasing systemic vascular resistance
    • Increasing mean circulatory filling pressure/mean systemic pressure
40
Q
  • What parameter has been changed to cause the shifts in the diagrams below?
A
  • TPR
  • Left diagram shows an increase in TPR which leads to a right shift of the cardiac function curve and a left shift of the vascular function curve
  • Right diagram shows a decrease in TPR which leads to a left shift of the cardiac function curve and a right shift of the vascular function curve
41
Q
  • What is the relationship between CO and venous return in an individual with heart failure?
A
  • Decreased inotropy
  • Decreased vascular complaince
  • Increased blood volume
  • Increased SVR

Cardiopulmonary Exam 2 (18 decks)

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