Exam #2: Cardiac Output

Question 1

What is cardiac output?

Answer 1

Heart Rate x Stroke Volume

CO=HR x SV (LVEDV- LVESV)

Question 2

What are the determinants of cardiac output?

Answer 2

1) Preload
2) Contractility
3) Afterload
4) Heart rate

*1-3= SV 
4= HR

Question 3

Draw the cardiac length-tension curve.

Answer 3

Y= Tension
X= Length 

Increased length= increased tension

Question 4

Draw the Frank-Starling Curve.

Answer 4

X= End diastolic volume 
Y= Intraventricular systolic pressure 

Increased EDV= increased developed tension & intraventricular systolic pressure

Question 5

Pathophysiology of heart failure.

Answer 5

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Question 6

What is the effect of decreased HR on Frank-Starling curve?

Answer 6

Decreased rate= increased EDV
Increased SV

CO maintained

Question 7

What is the effect of increased HR on Frank-Starling curve?

Answer 7

Increased HR= decreased EDV= decreased SV

CO maintained

Question 8

Draw the left ventricular volume & pressure curve.

Answer 8

N/A

A= mitral valve filling (ESV) 
B= mitral valve closed (EDV) 
C= Isovolumic contraction & aortic semilunar valve opens
D= Blood ejected into periphery & aortic valve closes

Question 9

What is preload?

Answer 9

End diastolic pressure when ventricle has become filled

- Venous return

Question 10

What is afterload?

Answer 10

Aortic pressure

• TPR
• Pressure the heart has to pump into/against

Question 11

Draw the Frank-Starling Curve on Pressure-Volume.

Answer 11

N/A

Question 12

What is the effect of increased preload on SV?

Answer 12

Increased SV

Question 13

Draw the Effect of Preload.

Answer 13

N/A

Question 14

What is the effect of afterload on SV?

Answer 14

Decreased SV

Question 15

Draw the effect of afterload on SV.

Answer 15

N/A

Question 16

Draw the Sarnoff curve of the heart.

Answer 16

N/A

Contraction curve

Question 17

Draw the effect of contractility with pressure-volume curve.

Answer 17

N/A

Question 18

What does a positive ionotropic agent do to the afterload curve?

Answer 18

Shifts the afterload curve upward

Question 19

What will a decrease in contractility to do to afterload curve?

Answer 19

Shift downward

Question 20

What is the difference between a systolic dysfunction & a diastolic dysfunction?

Answer 20

Systolic= unable to contract efficiently

Diastolic= unable to relax

Question 21

What is the Frank-Starling’s law of the heart?

Answer 21

Increased stretch of the sinus node, increases heart rate

Question 22

Draw the venous return curve. What happens when there is a sudden drop in venous return/ volume?

Answer 22

Decreased right atrial pressure & decreased systemic filling pressure

Question 23

Draw the venous return curve. What happens when there is a change in TPR i.e. vasodilation or vasoconstriction?

Answer 23

Changes in ateriolar resistance change what is coming back to the heart, but NOT overall pressure of systemic filling

Question 24

Draw cardiac function curves.

Answer 24

N/A

Question 25

Draw the cardiac function curves with autonomic control: maximal SNS, normal, sympathetic withdrawal, & PNS.

Answer 25

N/A

Question 26

How the sympathetic input effect CO?

Answer 26

Increases the force & rate of contraction

Question 27

How does SNS increase the force of cardiac contraction?

Answer 27

- Increased slope of phase 4 depolarization in nodal cells= increased HR - Alteration of Ca++ permeability (more inward)= increased contraction - Glyogenolysis= breakdown of glycogen (energy) BOTH= large increase in CO *Note that the SNS innervates the SA/AV nodes & cardiac myocytes

Question 28

How does parasympathetic input effect CO?

Answer 28

Massive decrease in heart rate

Question 29

Physiologically, what happens during systole with acute exercise because of sympathetic activity?

Answer 29

- Increased glycogenolysus leads to energy mobilization & enhanced substrate for contraction - Increase contractility via increasing Ca++ permeability during Phase 2 - Increased heart rate All leads to an increase in CO

Question 30

Physiologically, what happens during diastole with acute exercise because of sympathetic activity?

Answer 30

- Increased HR leads to decreased filling time - Changes in Ca++ permeability go BOTH ways i.e. enhanced efflux (Na+ -Ca++ exchanger) & sequestration Shorter relaxation & filling time but increased contractility & efficiency

Question 31

Draw the cardiac output & venous return curves.

Answer 31

N/A

Question 32

What is the equilibrium point of the cardiac output and venous return curves?

Answer 32

Right atrial pressure

Question 33

Draw the change that occurs with cardiac output and venous return with increases SNS innervation.

Answer 33

N/A

Question 34

How is cardiac output measured?

Answer 34

Fick Principle

Question 35

What is the Fick Principle?

Answer 35

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Question 36

What is the Indicator Dilution Method used to measure cardiac output?

Answer 36

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Question 37

List some factors that increase CO.

Answer 37

Reduced TPR - AV shunt - Hyperthyroidism - Anemia

Question 38

List some factors that decrease CO.

Answer 38

Heart damage - Ischemia - Valvular disease Decreased blood volume Acute venous dilation or obstruction Decreased tissue mass or tissue metabolism