Ventricular Function

Front 1

Define stroke volume

Back 1

volume of blood ejected by the ventricle per beat

Front 2

Stroke volume reflects the ability of the ventricular myocardium to develop?

Back 2

Tension and shorten

Front 3

SV is influenced by what three factors?

Back 3

preload, afterload, contractility

Front 4

What is the quantitative index of ventricular function?

Back 4

SV

Front 5

Define preload

Back 5

degree of stretch of myocardial fibers prior to contraction

Front 6

Preload is determined by?

Back 6

VEDV

Front 7

Frank-Starling law of the heart represents?

Back 7

the relationship between preload and SV

Front 8

Define afterload

Back 8

force against which the ventricle must work to eject blood

Front 9

What are components of afterload?

Back 9

PVR and aortic compliance

Front 10

Afterload is usually estimated by?

Back 10

SBP (for the left ventricle)

Front 11

Change in afterload can affect?

Back 11

SV

Front 12

What is one principal determinant of MVO2?

Back 12

Afterload

Front 13

Define contractility

Back 13

index of the force and extent of ventricular contraction

Front 14

Contractility is determined in part by?

Back 14

the chemical environment of the cell

Front 15

Contractility can be evaluated clinically with a?

Back 15

ventricular pressure-volume loop or by measuring EF

Front 16

What are some cardiac reserve mechanisms?

Back 16

Increase HR, preload, contractility, and ventricular hypertrophy

Front 17

Define cardiac output

Back 17

the volume of blood pumped by the heart each minute

Front 18

The afterload on the left ventricle may be considered to be the?

Back 18

aortic blood pressure, and afterload on the right ventricle may be considered to be the pulmonary artery blood pressure

Front 19

The afterload determines how much ______ the ventricular wall must develop before cell shortening and ejection can occur

Back 19

force

Front 20

An increased afterload will result in a decreased?

Back 20

SV

Front 21

When the chamber empties more completely due to an increase in contractility, ______ increases.

Back 21

stroke volume

Front 22

What is one major regulator of myocardial contractility?

Back 22

the activity of the sympathetic nerves that innervate the ventricular muscle cells.

Front 23

Ventricular function curves, plot?

Back 23

some index of ventricular function versus some index of preload, permit one to assess the inotropic state (contractility)

Front 24

Indices of ventricular function include?

Back 24

1. SV
2. SW
3. Rate of pressure development dP/dt

Front 25

Define stroke work

Back 25

is approximated by the product of MAP and SV.
SW= MAP x SV

Front 26

Indices of preload include?

Back 26

1. end-diastolic volume
2. end-diastolic pressure
3. MAP (filling pressure)
4. Muscle length/tension
5. Resting force

Front 27

The ventricular muscle mass increases from?

Back 27

volume overload and/or pressure overload (increased afterload)

Front 28

The ventricular cells tend to elongate when there is ?

Back 28

a volume overload

Front 29

The ventricular cells tend to thicken when there is?

Back 29

pressure overload

Front 30

When muscle cell length is at Lmax, thick and thin filament overlap is?

Back 30

optimal and force development and rate and extent of shortening are maximal

Front 31

At shorter cell lengths, thick and thin filament overlap is?

Back 31

suboptimal and force development and rate and extent of shortening are submaximal

Front 32

Also, at shorter lengths, there appears to be a decrease in?

Back 32

the amount of calcium released to the contractile proteins which may contribute to the reduced contractile function when the preload is reduced

Front 33

When cell length exceeds Lmax and the cells become overstretched, the overlap of thick and thin filaments is?

Back 33

suboptimal and force development and rate and extent of shortening are also submaximal

Front 34

What is a measure of preload?

Back 34

LVEDP

Front 35

Within limits, an increase in preload will lead to an _______ in stroke volume, if other factors remain unchanged.

Back 35

increase

Front 36

When preload changes, does the end-diastolic volume or the end-systolic volume change?

Back 36

End-diastolic volume *

Front 37

What is the Frank-Starling phenomenon?

Back 37

An increase in preload produces an increase in ventricular pump function (SV)

Front 38

With the Frank-Starling law, it is understood that the right and left ventricular output is?

Back 38

equal

Front 39

An increase in preload also leads to a?

Back 39

-increased MVO2
greater work output and elevated energy usage by the left ventricle

Front 40

* Afterload and shortening are _______ related.

Back 40

inversely*

Front 41

An increase in afterload will lead to a _____ in emptying, and, therefore a _______ in SV.

Back 41

decrease, decrease

Front 42

When afterload is increased, the volume ejected by the ventricle is? and what is increased?

Back 42

reduced and the residual (end-systolic) ventricular volume is increased

Front 43

What is the compensatory mechanism with an increased afterload?

Back 43

volume ejected from ventricle is reduced so there is an increase in residual (end-systolic) volume. If volume entering the ventricle during diastole is not changed, the preload for the subsequent contraction is increased and stroke volume tends to return to its original level.

Front 44

This compensatory mechanism is ______ driven.

Back 44

preload

Front 45

When is this preload compensation ineffective?

Back 45

when aortic pressure rises above 180 mmHg (SBP)

Front 46

If the heart muscle is not healthy, this compensation may be?

Back 46

inadequate

Front 47

With the preload compensation(increased afterload), do both EDV and ESV increase?

Back 47

yes

Front 48

T or F. The work of the heart and the oxygen requirements of the heart are increased dramatically by an increase in afterload?

Back 48

True

Front 49

When the contractile function of the myocardium is depressed, the heart cannot adequately respond to an increase in afterload and what falls?

Back 49

SV

Front 50

An increase in contractility produces?

Back 50

an increase in rate of force development (dP/dt), and an increase in the rate and extent of shortening

Front 51

An increase in contractility will tend to also increase?

Back 51

the emptying of the ventricular chamber, thus, increase ESV and SV.

Front 52

When contractility increases, preload (venous return) typically?

Back 52

remains unchanged or is increased.

Front 53

What happens to the pressure-volume loop with increasing SV when contracility is increased?

Back 53

shift to left

Front 54

What is responsible for the increased venous return in response to an increase in contracitility?

Back 54

venoconstriction, sympathetically mediated

Front 55

The sympathetic nerves that terminate on the heart release what neurotransmitter?

Back 55

NE

Front 56

NE does what to the ventricular muscle cells?

Back 56

produce an increase in contractility

Front 57

Activation of SNS leads to?

Back 57

1. Increased contractility
2. Increased diastolic filling (increased preload) which results from venoconstriction
3. Increased HR which results from the action of NE on the SA node.

Front 58

What other factors could increase contractility (5)?

Back 58

1. Increased ECF calcium concentration
2. Increased plasma levels of Epi and NE
3. Increased SNS activity
4. Decreased extracellular hydrogen ion concentration
5. Many drugs (including digitalis)

Front 59

What factors can decrease contractility (6)?

Back 59

1. Decreased ECF calcium
2. Depressed plasma levels of Epi and NE
3. Decreased SNS activity
4. Increased extracellular hydrogen ion concentration
5. Many drugs
6. Decreased O2 supply (hypoxia, hypoxemia)

Front 60

What are the cardiac reserve mechanisms?

Back 60

1. Increased HR
2. Increased SV (Increased EDV=increased preload, decreased ESV=increased contractility)
3. Increased ventricular mass (hypertrophy)

Front 61

Hypertrophy generally occurs in response to a?

Back 61

pathophysiological condition

Front 62

What are the two types of hypertrophy?

Back 62

1. Chamber dilation
2. Wall thickening

Front 63

Chamber dilation occurs when?

Back 63

the ventricle is required to pump excessive quantities of blood (volume overloaded)

Front 64

Wall thickening occurs when?

Back 64

the ventricle is required to pump against a high afterload (pressure overloaded)

Front 65

What can cause chamber dilation?

Back 65

incompetence of either the mitral or aortic valves

Front 66

If the mitral or aortic valve is incompetent, why does this cause hypertrophy?

Back 66

the ventricle is required to pump large quantities of blood per stroke if a significant amount of regurgitation is present

Front 67

In chamber dilation, hypertrophy occurs predominantly as a consequence of?

Back 67

cell elongation (eccentric hypertrophy)

Front 68

Cell elongation, causes the radius of the chamber to?

Back 68

increase

Front 69

With chamber dilation, the ventricular mass may _____, however, there is not generally a ______ in ventricular wall thickness

Back 69

triple, large increase

Front 70

The oxygen requirements of the ventricle may be?

Back 70

elevated markedly, the work of the ventricle is increase, which increases oxygen usage, and there is also more tissue to supply

Front 71

In chamber dilation, diastolic wall tension is?

Back 71

enhanced, T= P x radius

Front 72

Is the normal 1:1 ratio of myocardial fibers to capillaries maintained with chamber dilation?

Back 72

yes, just elongation of fibers and capillaries

Front 73

Concentric hypertrophy

Back 73

occurs as a consequence of cell thickening, diameters of individual fibers increase

Front 74

Wall thickening occurs when?

Back 74

the left ventricle is required to pump against an elevated afterload (pressure overloaded)

Front 75

What can cause concentric hypertrophy?

Back 75

Aortic stenosis or chronically elevated arterial BP (hypertension)

Front 76

Does the radius increase with concentric hypertrophy?

Back 76

not generally

Front 77

The pumping ability of the left ventricle is enhanced because of its?

Back 77

greater wall thickness

Front 78

Do oxygen requirements increase with concentric hypertrophy?

Back 78

yes, and oxygen delivery may be reduced.

Front 79

The greater ventricular mass requires an increased oxygen supply, the diffusion distances for oxygen are?

Back 79

increased, and the work of ejection is increased

Front 80

What occurs from the prolonged or chronic elevation in afterload?

Back 80

eventually it leads to a severe depression in contractility which may be caused by a defect in the cellular handling or calcium ions

Front 81

Which way does the ventricular function curve shift in response to 1. increased contractility and
2. decreased contractility

Back 81

1. Shifts up and to the left
2. Shifts down and to the right

Front 82

Which way does the ventricular function curve shift in response to 1. increased afterload and
2. decreased afterload

Back 82

1. Down and to the right
2. Up and to the left

Front 83

Is it more difficult to maintain a normal stroke volume if afterload is increased or decreased?

Back 83

increased, afterload reduction is a common and important therapeutic measure