Heart as a Pump

Question 1

what is cardiac ouptut

Answer 1

volume of blood pump per min (5 L/min at rest)

Question 2

equation for cardiac output

Answer 2

CO = HR x SV

Question 3

what is stroke volume

Answer 3

amount of blood pump per beat

Question 4

what controls heart rate

Answer 4

set by SA node

affected by autonomic NS

Question 5

what affects stroke volume (3 things)

Answer 5

1) preload (venous return)
2) afterload (resistance to flow - aortic pressure)
3) strength of contraction

Question 6

For LV what is preload ~ to?

Answer 6

end diastolic volume

Question 7

factors that affect preload

Answer 7

1) blood volume
2) filling pressure and time (HR)

3) resistance to filling
- RA pressure
- AV stensosis
- ventricular compliance

Question 8

Graph of EDPVR

what does graph mean

Answer 8

incr LV volume, incr LV pressure

Question 9

Graph of EDPVR

what does slope mean

Answer 9

inverse of ventricular compliance

steeper slope = decr compliance b/c harder for ventricle to fill (hypertrophy)

Question 10

how does hypertrophy affect EDPVR?

how does dilation affect EDPVR?

Answer 10

hypertrophy = steep slope = decr compliant

dilation = shallow slope = very compliant

Question 11

for LV what is afterload ~ to?

Answer 11

aortic pressure

Question 12

factors affecting afterload

Answer 12

1) aortic pressure
2) wall stress so wall thickness and radius (T= dP * R / u(thickness))
3) aortic stenosis

Question 13

what is inotropy

Answer 13

contractility - force of contraction independent of fiber length

describes systolic fxn of heart

Question 14

what is the biggest factor affecting inotropy

Answer 14

sympathetic tone

Question 15

what is shown on EDPVR

Answer 15

P-V relationship during filling of heart BEFORE CONTRACTION

Question 16

what does EDPVR slope mean

Answer 16

passive elastic properties of heart

slope = inverse of compliance
steeper = less complaint

Question 17

EDPVR represents the ___ on the left ventricle

Answer 17

PRELOAD

Question 18

what is shown on systolic pressure-volume relationship

Answer 18

P-V relationship at PEAK OF ISOMETRIC CONTRACTION

Question 19

compare slopes of EDPVR vs. systolic PV relationship

Answer 19

Systolic P-V relationship is steeper (pressure incr a lot for small change in volume

Question 20

what properties are included in systolic PV relationship

Answer 20

ACTIVE + PASSIVE

Question 21

how do you create the Starling (ventricular function) curve

Answer 21

subtract SPVR from EDPVR

Question 22

what does starling curve represent?

Answer 22

active tension

Question 23

what are all the possible y axes for Starling curve

Answer 23

ventricular fxn on y-axis = tension, CO, stroke volume

Question 24

what are all the possible x axes for Starling curve

Answer 24

preload on x-axis = length, pressure, or EDV

Question 25

what does frank-starling law of heart describe (3 things)

Answer 25

1) heart ALWAYS ON ASCENDING LIMB OF STARLING CURVE
2) heart responds to incr in EDV with incr in force
3) what goes in heart must come out

Question 26

what does a violation of frank starling law lead to?

Answer 26

HEART FAILURE

Question 27

HOW DOES incr preload affect PV loop?

Answer 27

shift EDV to the right

more EDV, so heart contract with more force to ensure same end systolic volume

–> INCR STROKE VOLUME

Question 28

How does incr afterload affect PV loop?

Answer 28

shift end systolic volume to the right and shift top pressure line up

incr aortic pressure = heart work harder to eject, less time
incr end systolic volume (can’t empty)

–> DECR STROKE VOLUME

Question 29

How does incr inotropy affect PV loop?

Answer 29

new Starling curve

shift top line up and shift end systolic volume to the left

peak pressure higher
–> INCR STROKE VOLUME (until return to original)