Pressure-Volume relationship - Cardiovascular Phys. Flashcards
What 4 things affect cardiac output?
- Heart rate
- Contractility
- Preload
- Afterload
What is the equation for cardiac output?
SV X HR
What is stroke volume?
Volume of blood ejected by ventricle with each beat
What is the equation for stroke volume?
EDV - ESV
end diastolic volume - end systolic volume
What is ejection fraction?
Fraction of EDV ejected in each stroke volume
What is cardiac output?
Total volume of blood ejected by ventricle per minute
Normal value for SV?
70 mL
Normal value for ejection fraction?
55%
Normal value for cardiac output?
5 L
What is preload?
Amount of blood ready to be pumped out – EDV
At steady state, what should cardiac output be equal to?
Venous return
What is afterload?
Force opposing contraction during ejection
– pressure required to eject blood
EDPVR
End diastolic pressure volume relationship
ESPVR
End systolic pressure volume relationship
For EDPVR, increases in volume ____ increase pressure
Do not greatly
For ESPVR, increases in volume ___ increase pressure
DO
ESPVR curve is used to illustrate?
CONTRACTILITY
On the pressure-volume graph, what occurs at point A?
Mitral (bicuspid) valve opens and ventricular filling begins (diastole)
On the pressure-volume graph, what occurs at point B?
Mitral (bicuspid) valve closes and isovolumetric contraction begins
On the pressure-volume graph, what occurs at point C?
Aortic valve opens and ejection begins
On the pressure-volume graph, what occurs at point D?
Aortic valve closes and isovolumetric relaxation begins
On the pressure-volume graph, point A is what volume?
ESV
On the pressure-volume graph, point B is what volume?
EDV
On the pressure-volume graph, the length of point A to point B represents what volume?
Stroke volume
Decreased preload, would affect the pressure-volume graph how?
Less blood to be pumped out = DECREASED EDV
Increased afterload, would affect the pressure-volume graph how?
Increased pressure to overcome to eject blood = INCREASED pressure to open aortic valve (point C)
INCREASED ESV - decrease SV
Decreased afterload, would affect the pressure-volume graph how?
Decreased pressure to overcome to eject blood = DECREASED pressure to open aortic valve (point C)
DECREASED ESV - increased SV
Increased contractility _____ ESV
DECREASES
Decreased contractility _____ ESV
INCREASES
Increased contractility ____ stroke volume
Increases
