Cardiac Muscle Mechanics

Question 1

What are the 3 independent variables that influence systolic performance..

Answer 1

preload
contractility
afterload

Question 2

What are the best indices of preload?

Answer 2

left ventricular end diastolic volume (LVEDV)
left ventricular end diastolic pressure (LVEDP)

Question 3

What are some other indices for measuring preload that are considered less reliable?

Answer 3

central venous pressure (CVP)
pulmonary capillary wedge pressure (PCWP)
Rt atrial pressure (RAP)

Question 4

What are some indices for contractility?

Answer 4

EF ejection fraction

Question 5

Label the numbers and what this graph is saying.

Answer 5

Question 6

If contractility determines systolic interval; then what determines diastolic interval?

Answer 6

HR

Question 7

What are 3 main situations in which afterload is affected?

Answer 7

when aortic pressure is increased because of HTN

When SVR increased

aortic stenosis

Question 8

How would increasing afterload and decreasing contractility affect a ventricular function curve?

Answer 8

shift curve down and to the right

Question 9

How would decreasing afterload and increasing contractility shift a ventricular function curve?

Answer 9

shift it up and to the left

Question 10

What does the Y axis on a ventricular function curve represent?

Answer 10

systolic peformance

may be also referred to as:
stroke work
stroke volume
cardiac output

Question 11

What does the X-axis on a ventricular function curve represent?

Answer 11

the preload

may be referred to as:
ventricular end-diastolic volume or pressure
RAP, CVP

Question 12

What does A represent in this graph?

Answer 12

decreased performance due to a reduction in preload

Question 13

What does B represent in this graph?

Answer 13

increased performance due to an increased preload

Question 14

What does point N to C represent on this graph?

Answer 14

increased performance due to an increase in contractility or reduction in afterload

Question 15

What do point C, D, E in this graph represent?

Answer 15

different levels of performance due to changes in preload only all three points have the same contractility

Question 16

What does Vector I represent?

Answer 16

loss in preload leading to decreased performance (i.e hemorrhage, venodilators (nitroglycerin)

Question 17

What does Vector II represent?

Answer 17

Question 18

What does Vector III represent?

Answer 18

Question 19

What does Vector IV represent?

Answer 19

Question 20

What is End-diastolic volume (EDV)?

Answer 20

volume of blood in the ventricle at end of diastole

Question 21

What is ESV?

Answer 21

end systolic volume is volume of blood in ventricle at end of systole

Question 22

What is Stroke volume?

Answer 22

volume of blood ejected by the ventricle per beat

Question 23

Formula for SV?

Answer 23

SV = EDV - ESV

Question 24

What is the formula for EF?

Answer 24

ejection fraction is EF = SV/EDV

Question 25

What is EF?

Answer 25

The fraction or percentage of blood pumped out of the heart

Question 26

What is normal EF?

Answer 26

> 55%

Question 27

Systolic dysfunction.

Answer 27

an abnormal reduction in ventricular emptying due to impaired contractility or excessive afterload

Question 28

What is diastolic dysfunction?

Answer 28

a reduction in ventricular compliance i.e the ventricle is stiffer

Question 29

What is dilated cardiomyopathy?

Answer 29

ventricular dilation with only a modest hypertophy leads to systolic dysfunction

Question 30

What is restrictive cardiomyopathy.

Answer 30

is decreased ventricular compliance with diastoic dyfunction

Question 31

What is hypertrophic cardiomyopathy.

Answer 31

septal or left ventricular hypertrophy unrelated to pressure overload

diastolic dyfunction due to increased muscle stiffness and impaired relaxation

hypertrophy may be related to “septal fiber disarray”