cardiac pressure volume loop Flashcards
what is the equation for work done by the ventricle muscle?
work= pressure x volume change
what is occurring during isovolumic contraction in the ventricle?
heart is still contracting without changing volume
what is occurring during isovolumic relaxation in the ventricle?
heart is relaxing without changing volume
what is occurring during the “mitral valve open to mitral valve close” phase in the cardiac cycle?
ventricle is filling with blood
there is an increase in pressure due to increase in passive tension as the ventricle muscle stretches
what is the “increase in passive tension” called?
preload
what is the end-systolic pressure volume relationship (ESPVR)?
the curve that describes that maximal pressure that can be developed by the ventricle at any given LV volume
what is the inverse of compliance?
elastance
what is the equation for compliance?
change in volume/change in pressure
in describing the ventricle filling, what does a high compliance/low elastance mean
that the ventricle is “easy” to fill
what happens to the ESPVR curve as inotropy (contactility) increases?
curve becomes steeper and shifts to the LEFT
what happens to the ESPVR curve as inotropy (contactility) decreases?
becomes flatter and shifts to the RIGHT
what does a steeper EDPVR slope mean regarding compliance
what is an example of when this could happen?
indicates decreased compliance
ex. in ventricular hypertrophy
what does a flatter EDPVR slope mean regarding compliance
what is an example of when this could happen?
indicates increased compliance
ex. dilated cardiomyopathy
what does end diastolic pressure volume relationship curve describe?
the passive filling curve for the ventricle (and thus passive properties of the myocardium)
after the ventricle reaches is end diastolic volume and the mitral valve closes, what occurs?
muscle begins to actively contract and pressure increases rapidly (isovolumetrically) until the aortic valve opens
what is the afterload?
the point when the blood pressure in the ventricle equals or exceeds the blood pressure in the aorta
what word does this definition describe?
“volume of blood ejected by the ventricle in a single contraction”
stroke volume
in what type of situation is stroke volume sensitive to afterload changes?
in a failing heart, normally SV is NOT greatly influenced by afterload
define ejection fraction
fraction of end diastolic volume that is ejected out of the ventricle during each contraction
EF= SV/EDV
in a healthy ventricle, what is the usual ejection fraction?
greater than .55
low EF is usually indicative of what?
systolic dysfunction
if the EF is lower than .2 what is the heart at risk for?
severe heart failure
increased enotrophy does what to the EF?
increases it
define preload
the EDV at the beginning of systole
what is preload and afterload measured in?
preload is in volume
afterload is in pressure mmHg
increasing aortic pressure does what to the amount of work that the heart has to do?
increases it
increasing stroke volumes will do what to the amount of work that the heart has to do?
increase it because they heart has to move more blood
increasing the preload will do what to the tension and stroke volume?
increase it
increasing ventricular afterload does what to stroke volume and ejection fraction?
it decreases stroke volume and ejection fraction
what does norepi do to:
stroke volume
ejection fraction
contractility
increase SV
can increase EF
increase contractility
how does cardiomyopathy and heart failure normally effect CO
decrease it
how does infection and sepsis normally affect CO
increase cardiac output
