Contractility & Cardiac Output

Question 1

Define SV and its equation

Answer 1

The vol of blood ejected by LV in a single beat

SV = EDV - ESV

Question 2

Define EF and its equation

Answer 2

Fraction of the EDV ejected with each SV

EF = SV/EDV

Question 3

What is a normal EF

Answer 3

55%

Question 4

Define CO and its equation

Answer 4

Total vol. ejected by the ventricle per unit time

CO - SV x HR

Question 5

An increase in afterload means what in terms of velocity of contraction

Answer 5

Decreased velocity and more ESV

Question 6

Define the FSL

Answer 6

Col. of blood ejected by the LV is = to the vol. present in the ventricle at the end of diastole (EDV)

Question 7

An increase in VR means what

Answer 7

An increase in EDV and an increase in SV and pressure on LV

Question 8

Positive inotropic stimulation means what in terms of SV and LVEDV

Answer 8

Increased SV and increased EDV

Question 9

What is the most accurate definition of EDV? What is another way of determining this

Answer 9

The amount of wall tension in LV just before contraction

Another way is the pressure in the chamber just before contraction

Question 10

Increased VR means what in terms of EDV and pressure and SV

Answer 10

Increased EDV and increased P and increased SV

Question 11

What happens in increased after-load

Answer 11

LV must generate higher pressure in IV Contraction to overpower Ao. Pressure and open AoSLV

LV become hypertrophic which leads to heart failure and increased ESV

Question 12

Does EDV increase with increased contractility

Answer 12

Yes

Question 13

Cardiac work is directly proportional to what

Answer 13

Pressure work

Question 14

Define stroke work and give the equation

Answer 14

Work done per each beat

SW = SV x AoP

Question 15

Define cardiac minute work and give the equation

Answer 15

Work per unit time

CMW = CO x AoP

CO is considered external work while AoP is considered internal (pressure) work

Question 16

Myocardial O2 consumption correlates directly with what

Answer 16

CMW

Question 17

Pressure work (AoP) is what compared to external work

Answer 17

More costly in O2 demand than in CO

So we burn more O2 in OV Contraction than in actual ejection of blood from the heart

Question 18

How would Ao. Stenosis affect myocardial O2 demand

Answer 18

Ao. Stenosis means increased Aop which means an increased O2 demand

Question 19

What receptor innervates the myocytes for sympathetic innervation

Answer 19

B1

Question 20

The parasympathetic N.S innervates which part of the heart only

Answer 20

The atria

Question 21

Atrial systole takes place when in the EKG

IV Contraction

Rapid Ven. EJ

IV Relaxation

Rapid Vent Filling

Answer 21

PR

QRS with S1

ST segment

Post T wave with S2

Way post T wave

Question 22

A decreased mean systolic pressure means what in terms of CO

Answer 22

A decreased CO

Question 23

What is indicated at the equilibrium point

Answer 23

CO = Preload = EDV = VR

Question 24

At extremely high pressures, what happens to CO

Answer 24

It levels off and does not increase anymore

Question 25

Define the mean systemic pressure

Answer 25

RA pressure where VR = 0

Question 26

What two things influence MSP

Answer 26

Blood volume

Distribution of blood between unstressed and stressed volumes

Question 27

If Blood Vol is higher than normal, unstressed vol. is already “full”, so what happens to remaining volume and what does this mean for MSP and intersection point

Answer 27

Shifted to the stressed volume

MSP is increased, and intersection point shifts R causing a higher CO

Question 28

If blood volume is decreased, what does this mean for the stressed and unstressed volume and the equilibrium

Answer 28

A decreased MSP and a shift left, causing a decreased CO

Question 29

What does a positive and negative inotropic effect cause in terms of the equilibrium and the MSP and CO and pressure

Answer 29

Positive:
Left shift due to increased contraction and thus an increased SV

Negative:
Right shift with a decreased SV

Question 30

What happens in cardiac failure in regards to inotrpoy, compliance, and Blood volume

Answer 30

Decreased inotropy which means decreased vascular compliance, but increased blood volume and increased resistance