Cardiac output and Venous Return

Question 1

What is a cardiac function curve?

Answer 1

Left ventricular cardiac output plotted as a function of right atrial pressure

Question 2

What does the plateau of a cardiac function curve represent?

Answer 2

There is a maximum cardiac output regardless of increasing venous return at some point

Question 3

What conditions can cause a hypereffective heart?

Answer 3

Sympathetic stimulation

Athletic conditioning

Question 4

What conditions can cause a hypoeffective heart?

Answer 4

Decreases ympathetic stimulation

Inefficient pumping

Reduced filling

Increases afterload

Question 5

What is the relationship between cardiac output and peripheral resistance?

Answer 5

Cardiac output varies inversely with peripheral resistance

Question 6

What is a venous return curve?

Answer 6

Show the effect of right atrial pressure on venous return

As right atrial pressure increases, venous return decreases

Question 7

What is the reason for the plateau in a venous return curve?

Answer 7

Large veins in the thoracic cavity collapse as BP falls below atmospheric pressure, impeding flow of blood to the heart and causes venous return to level off

Question 8

What factors affect venous return to the heart?

Answer 8

Right atrial pressure

Mean systemic filling pressure

Resistance to flow between peripheral vessels and righ atrium

Question 9

What is the mean systemic filling pressure (Psf)?

Answer 9

The pressure at which the venous pressure and arterial pressure are equalized at when the heart is stopped

The point at which the venous return curve intersects with the right atrial pressure axis

Question 10

What is the mean systemic filling pressure dependent on?

Answer 10

Blood volume and vascular compliance

Question 11

What conditions directly alter the venous return curve?

Answer 11

Change in blood volume - direct

Change in venous tone - direct

Resistance to venous return

Question 12

How do changes in resistance affect the venous return curve?

Answer 12

It effects the slope of the graph

Decreases resistance increases the slope and vice versa

Question 13

What is the equilibrium point when a cardiac output and venous return curve a plotted together?

Answer 13

The point at which CO is equal to venous return

Anything that shifts either of the curves will shift the equilibrium point

*Study the various examples in the slides