Cardiac Muscle Mechanics Flashcards
What are the 3 independent variables that influence systolic performance..
preload
contractility
afterload
What are the best indices of preload?
left ventricular end diastolic volume (LVEDV)
left ventricular end diastolic pressure (LVEDP)
What are some other indices for measuring preload that are considered less reliable?
central venous pressure (CVP)
pulmonary capillary wedge pressure (PCWP)
Rt atrial pressure (RAP)
What are some indices for contractility?
EF ejection fraction
Label the numbers and what this graph is saying.
If contractility determines systolic interval; then what determines diastolic interval?
HR
What are 3 main situations in which afterload is affected?
when aortic pressure is increased because of HTN
When SVR increased
aortic stenosis
How would increasing afterload and decreasing contractility affect a ventricular function curve?
shift curve down and to the right
How would decreasing afterload and increasing contractility shift a ventricular function curve?
shift it up and to the left
What does the Y axis on a ventricular function curve represent?
systolic peformance
may be also referred to as:
stroke work
stroke volume
cardiac output
What does the X-axis on a ventricular function curve represent?
the preload
may be referred to as:
ventricular end-diastolic volume or pressure
RAP, CVP
What does A represent in this graph?
decreased performance due to a reduction in preload
What does B represent in this graph?
increased performance due to an increased preload
What does point N to C represent on this graph?
increased performance due to an increase in contractility or reduction in afterload
What do point C, D, E in this graph represent?
different levels of performance due to changes in preload only all three points have the same contractility
What does Vector I represent?
loss in preload leading to decreased performance (i.e hemorrhage, venodilators (nitroglycerin)
What does Vector II represent?
What does Vector III represent?
What does Vector IV represent?
What is End-diastolic volume (EDV)?
volume of blood in the ventricle at end of diastole
What is ESV?
end systolic volume is volume of blood in ventricle at end of systole
What is Stroke volume?
volume of blood ejected by the ventricle per beat
Formula for SV?
SV = EDV - ESV
What is the formula for EF?
ejection fraction is EF = SV/EDV
What is EF?
The fraction or percentage of blood pumped out of the heart
What is normal EF?
> 55%
Systolic dysfunction.
an abnormal reduction in ventricular emptying due to impaired contractility or excessive afterload
What is diastolic dysfunction?
a reduction in ventricular compliance i.e the ventricle is stiffer
What is dilated cardiomyopathy?
ventricular dilation with only a modest hypertophy leads to systolic dysfunction
What is restrictive cardiomyopathy.
is decreased ventricular compliance with diastoic dyfunction
What is hypertrophic cardiomyopathy.
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”
