2.4.2 Myocardial Performance

Question 1

Peak ventricular systolic pressure?

Answer 1

maximal pressure achieved during ejection

Question 2

What is reduced in ventricular hypertrophy? What is a common cause?

Answer 2

Ventricular compliance (increased contractility w/ decreased filling)

Common cause: chronic systemic HTN

Question 3

What would you expect to be altered in ventricular hypertrophy that isn’t altered by SYM firing?

Answer 3

Diastolic filling curve

Both affect the contractility

Question 4

On Starling’s curve, stroke volume will increase as EDV increases up to a point. Then, the SV will decrease as EDV continues to increase. Why is this?

Answer 4

This is due to overstretching which causes the overlap of thick and thin filaments to become suboptimal.

Question 5

What is the equation for SV?

Answer 5

EDV - ESV

Question 6

Describe how decreased inotropic state would change a P-V loop.

Answer 6

Same aortic DP

Same EDV

Decreased contractile force

Decreased SV (increased ESV)

Reduced ejection fraction (EF)

Question 7

Where do the components of an EKG and heart sounds match up to points on a pressure-volume loop?

Answer 7

Question 8

What is the difference b/t the ionotropic reserve and Starling reserve?

Answer 8

Starling reserve: maximal increase in SV that can be achieved by increasing EDV

Inotropic reserve: the extent that increased contractility can raise SV

Question 9

Answer 9

B

Question 10

How do changes in inotropic state alter the Starling curve?

Answer 10

Increased inotropy: upward shift of curve

Decreased inotropy: downward shift of curve

Question 11

What are some ways that TPR is decreased due to systemic ateriolar dilation (altered afterload)?

Answer 11

1. Vasodilator administration
2. Anaphylactic shock

Question 12

What is true about intracellular calcium contrations at all points along a single Starling curve?

Answer 12

It is the same at all points

Question 13

The area within the P-V loop represents what?

Answer 13

Stroke work

Question 14

How can parasympathetic innervation of the heart affect CO?

Answer 14

Decrease HR by decreasing # of sodium funny channels

Question 15

Answer 15

B

Question 16

How can sympathetic innervation of the heart change CO?

Answer 16

1. Increase HR (increase sodium funny channels)
2. Increase preload (increases SV)
3. Increase afterload (decreases SV)
4. Increase inotropic state (increases SV)

Question 17

Summarize the effects that changes in inotropy, afterload, HR, and venous return can have on the Starling curve.

Answer 17

Question 18

Describe how decreased afterload would affect a P-V loop.

Answer 18

Same inotropic state

Same EDV

Decreased aortic DP

Decreased systolic pressure

Increased SV (decreased ESV)

Question 19

What does inotropic state refer to?

Answer 19

The force of contraction (contractility)

Question 20

What is a third way to alter afterload despite no change in TPR?

Answer 20

Aortic stenosis

Question 21

Answer 21

C

Question 22

Answer 22

A

Question 23

What are the two main determinants of preload?

Answer 23

1. Filling Time (HR)
2. Rate of venous return (venous tone, blood volume, gravity)

Question 24

What are some measures or variables related to preload?

Answer 24

EDV

Venous return

End-diastolic pressure

Question 25

What is afterload?

Answer 25

Defined as ventricular wall tension during ejection. It is the resistance that must be overcome to eject blood.

Question 26

Describe the process in which venous pressure is increased in both types of heart failure (systolic and diastolic dysfunction)

Answer 26

Question 27

What are some of the indices of afterload?

Answer 27

Aortic diastolic pressure (when aorta opens) or aortic systolic pressure

Question 28

What are the two reasons that ventricular filling is impaired in diastolic dysfunction?

Answer 28

Increased stiffness of the ventricular wall Reduced ventricular relaxation during diastole

Question 29

What are some ways to decrease inotropy? (4)

Answer 29

1. Decrease SYM firing 2. Beta antagonist 3. Ca Channel blocker 4. Heart failure

Question 30

What is preload?

Answer 30

Defined as stretch on the myocardial fibers before contraction Related to ventricular filling

Question 31

What is represented by the isovolumic curve?

Answer 31

Maximal pressure that can be developed at any ventricular volume (same shape as the Starling curve)

Question 32

What might be responsible for the shifts from 1 to 3 and 1 to 2 along the starling curve?

Answer 32

1 to 3: Increased HR or decreased venous return 1 to 2: Decreased HR or increased venous return

Question 33

What are the three key components seen in a P-V loop due to L ventricular systolic dysfunction?

Answer 33

The P₀ curve is shifted downwards Same passive filling curve Increased EDV

Question 34

Distinguish b/t preload and afterload.

Answer 34

Preload: ventricular filling which occurs prior to contraction Afterload: force the ventricle has to overcome during ejection, so it involves factors after ventricular contraction begins

Question 35

How do skeletal muscle and cardiac muscle differ in regards to their inotropic state?

Answer 35

Skeletal muscle: cytosolic Ca++ levels are supramaximal during contraction Cardiac muscle: cytosolic Ca++ levels are subramaximal for cross-bridge activation (Thus, altering Ca++ levels in contracting myocytes will result in formation of more cross bridges and increased contractile force)

Question 36

What are some ways that TPR is increased due to systemic ateriolar constriction (altered afterload)?

Answer 36

1. Administer a vasocontrictor 2. Some forms of HTN (chronic)

Question 37

What are two ways that force of contraction is enhanced?

Answer 37

Sympathetic nerves and cardiac glycosides (these block Na/K ATPase causing the sodium/calcium exchanger to pump Na out while pumping in Ca causing increased contractility)

Question 38

Describe how increased inotropic state would change a P-V loop.

Answer 38

Same aortic DP Same EDV Increased contractile force Increased SV (decreased ESV) Increased SP

Question 39

If aortic DP was increased (everthing else remains the same), how would the ejection rate change?

Answer 39

The ejection rate would decrease b/ there would be a smaller difference in P₀ - DP

Question 40

What two curves are used to to contruct a pressure-volume loop?

Answer 40

End-systolic pressure volume curve, P_o, and Diastolic filling curve aka isovolumic and filling curves, respectively

Question 41

Answer 41

D

Question 42

What differentiates systolic dysfunction from diastolic dysfunction

Answer 42

Systolic dysfunction decreases EF compared to normal

Question 43

What is the ventricular end-diastolic pressure?

Answer 43

Pressure at the end of filling at the time that the QRS complex occurs

Question 44

Decribe how increased preload would change P-V loop.

Answer 44

Same inotropic state Same aortic diastolic pressure Increased EDV Increased systolic pressure Increased SV

Question 45

Draw out a pressure-volume loop and label its key elements.

Answer 45

Question 46

Describe how diastolic dysfunction would alter a P-V loop.

Answer 46

Question 47

Where is edema located in each of the forms of heart failure? (R and L)

Answer 47

R: edema in the systemic organs L: pulmonary edema due to increased pulmonary venous pressure

Question 48

Describe how decreased preload would change a P-V loop.

Answer 48

Same inotropic state Same aortic DP Decreased sytolic pressure Decreaed EDV **Decreased SV**

Question 49

What are some ways to increase inotropy?

Answer 49

1. SYM nerve firing 2. Beta agonist 3. Cardiac glycoside

Question 50

What can used to determine the rate of ejection?

Answer 50

P₀ - Aortic DP

Question 51

Why is looking at a starling curve in terms of SV versus EDV limiting as compared to stroke work versus EDV?

Answer 51

In a SV v. EDV curve, increased inotropy cannot be distinguished from decreased afterload. The stoke work versus EDV curve is unaffected by afterload, so it can distinguish b/t an inotropic change and a change in afterload.

Question 52

Why does contractile force increase at greater preloads?

Answer 52

The stretch results in more favorable overlap of thin and thick filaments.

Question 53

What does Starling's Law of the heart state?

Answer 53

Stoke volume increases when preload is increased.

Question 54

Answer 54

D

Question 55

Describe how increased afterload would change a P-V loop.

Answer 55

Same inotropic state Same EDV Increased Aortic DP Decreased SV (increased end-systolic volume)

Question 56

Describe how ventricular hypertrophy would change a P-V loop.

Answer 56

Increase inotropy Increase aortic DP Decrease EDV Increase EDP

Question 57

How do changes in inotrophy shift a Starling curve that is based off stroke work verses EDV?

Answer 57

It is the same as looking at SV vs. EDV

Question 58

How do changes in afterload affect the Starling curve?

Answer 58

Decreased afterload: Shift Starling curve up (increased SV) Increased afterload: Shift Starling curve downward (decreased SV)