Cardiac performance

Question 1

What is the relationship between afterload and velocity of shortening?

Answer 1

The greater the afterload the slower the velocity of shortening

Question 2

How does preload affect the force-velocity relationship?

Answer 2

If preload is increase there will be a greater velocity of shortening at a given afterload

Question 3

How does preload affect the length-tension relationship?

Answer 3

If preload is increased there is an increase in active tension development

Question 4

Does changing the preload affect Vmax?

Answer 4

No

Question 5

What is directly proportional to the volume of blood in vena cavae and venous tone?

Answer 5

Central venous pressure

Question 6

What will occur to central venous pressure in hypovolemia or venodilation?

Answer 6

It will decrease

Question 7

What will occur with central venous pressure in hypervolemia or venoconstriction?

Answer 7

It will increase

Question 8

What is the use of pulmonary capillary wedge pressure?

Answer 8

It provides an estimate of LV end-diastolic pressure and LA pressure

Question 9

What does a PCWP of >20 mmHg indicate?

Answer 9

Pulmonary edema

Question 10

What are factors that increase preload?

Answer 10

Increased ventricular compliance
Decreased venous compliance/venoconstriction
Increased force of atrial contraction
Reduced HR
Increased aortic pressure
Increased venous return

Question 11

What are factors that decrease preload?

Answer 11

Decreased venous blood pressure from hypovolemia
Impaired atrial contraction
Increased HR
Decreased ventricular afterload
Decreased ventricular compliance
AV valve stenosis

Question 12

What is another name for decreased ventricular compliance?

Answer 12

Ventricular diastolic failure

Question 13

What increases end-systolic volume?

Answer 13

Increased afterload
Decreased contractility

Question 14

What increases end-diastolic volume?

Answer 14

Increased venous return
Increased preload

Question 15

What is the equation for wall stress?

Answer 15

Wall stress = (P x r)/(2 x wall thickness)

Question 16

What is the equation for law of LaPlace?

Answer 16

T = P x r

Question 17

How does the LV compensate for increased afterload?

Answer 17

Hypertrophy

Question 18

What are factors that can increase afterload?

Answer 18

Aortic valve disease
Increased vascular resistance

Question 19

What is the average stroke volume in healthy persons?

Answer 19

70 mL

Question 20

What is the equation for SV?

Answer 20

SV = EDV - ESV

Question 21

What is the most important determinant of stroke volume?

Answer 21

EDV

Question 22

What increases SV?

Answer 22

Increased contractility
Increased preload
Decreased afterload

Question 23

What are the only mechanisms that can alter force generation in the heart?

Answer 23

Changes in fiber length
Changes in inotropy

Question 24

What occurs with increased cardiac inotropy?

Answer 24

Increases velocity of fiber shortening with increases the rate of ventricular pressure development

Question 25

What is a reliable marker for contractility?

Answer 25

Rate of pressure change = deltaP/deltat

Question 26

How does inotropy affect the force-velocity relationship?

Answer 26

Increase in inotropy results in an increase in Vmax and Fmax (maximal isometric force)

Question 27

What is the equation for stroke work?

Answer 27

Stroke work = aortic pressure x SV

Question 28

What is represented by the area within a pressure-volume loop?

Answer 28

Stroke work

Question 29

What is the primary energy source for stroke work?

Answer 29

Fatty acids

Question 30

What will change in a PV loop from exercise?

Answer 30

Increased EDV Decreased ESV Increased SV Increased LV pressure

Question 31

What will change in a PV loop in AV shunts?

Answer 31

Increased EDV Increased SV Decreased LV pressure ESV stays the same

Question 32

What will change in a PV loop associated with aortic stenosis?

Answer 32

Increased LV pressure Increased ESV Decreased SV from increased afterload

Question 33

What is the equation for ejection faction?

Answer 33

EF = SV/EDV = (EDV-ESV)/EDV

Question 34

What is a normal EF?

Answer 34

Greater than or equal to 55%

Question 35

What is EF an index of?

Answer 35

Ventricular contractility

Question 36

What is the difference in EF between diastolic and systolic HF?

Answer 36

EF decreases in systolic HF and stays normal in diastolic HF

Question 37

What factors are directly proportional to EF?

Answer 37

Preload Contractility/inotropy

Question 38

What is the relationship between afterload and EF?

Answer 38

Inversely proportional