Physio - Cardio output + Venous return

Question 1

Effects of Blood Volume, Venous Compliance, and Vascular Resistance related to

Venous Return: Summary

Answer 1

VR is additionally affected by…

• muscle contraction
• respiratory activity
• vena cava compression
  
  • (e.g. Valsalva, pregnancy), gravity

Notes:

• MSP = Mean systemic pressure
• VR = Venous return

Question 2

Effects on Cardiac Performance: Summary

Answer 2

Question 3

Cardiac Cycle

Answer 3

Basics:

• sequence of electrical & mechanical events occuring in a single heart beat

Timing:

• Occure more/less simulataneously in left/right heart
• Difference = left heart everything is at a HIGHER pressure

Note:

• New regulation = 130/80 is now hypertensive

Question 4

What does the cardiac loop look like for Aortic Regurgitation?

Answer 4

Question 5

What does the cardiac loop look like for Aortic Stenosis?

Answer 5

• Increased preload
• Increased afterload
• Decreased SV

Question 6

What does the cardiac loop look like for Mitral Stenosis?

Answer 6

• Increased SV
• Increased EDV

Question 7

What is the importance of a Cardiac and Vascular function curve?

Answer 7

Basics:

• Cardiac function curve = CO depends on EDV
• Vascular function curve = VR & relationship to right atrial pressure

Equilibrium point:

• CO = VR
  
  • dot on graph

How to change CO:

• alter…
  
  • VR curve
  • CO curve
  • or change both simultaneously

Question 8

Inotropic Effects alter the Cardiac Function Curve

Answer 8

Positive inotropic agents

• ex: digitalis (Foxglove)
• Causes: ↑ contractility & ↑ CO
  
  • EQ = shifts to ↑ CO & ↓ RAP

Negative inotropic agents

• ex: ACh
• Causes: ↓ Contractility & ↓ CO
  
  • EQ = shifts to ↓ CO & ↑ RAP

Note:

• Intracellular Ca
  
  • only affects artery output!
• Increased in RAP
  
  • leads to ↑ SV & CO

Question 9

Changes in Blood Volume and Venous Compliance

Answer 9

Changes in Blood Volume & Venous Compliance

• alter Mean Systemic Pressure –> hence affect the
  Vascular Function Curve

Basics:

• MSP is ↑ by an ↑ in blood volume
• MSP is ↑ by a ↓ in venous compliance (stiffer vessels) ->
  
  • shift of blood towards stressed volume
• ↑ mean systemic pressure shifts curve to the right

Question 10

How do Changes in TPR affect Cardiac
Function & Venous Return Curve?

Answer 10

Basics:

• Slope of VR = TPR
  
  • primarily from arterioles
• Change in TPR affects both CO & VR

Effect on Cardiac Function & VR:

• ↑ TPR = CCW rotation in vascular function
  
  • ↓ VR & ↓ CO

Note:

• Changing peripheral resistance CAN cause the CO to shift w/o changing the RAP

Question 11

Explain the left ventricular & aortic pressure changes of a patient
with aortic valve stenosis.

Answer 11