P-V curve Flashcards
Frank Starling relationship is based on ____ relationship. Why?
length-tension relationship in the ventricle
incr in EDV, incr ventricular fiber length, incr tension
What is the mechanism that matches CO to venous return
Frank starling relationship,
greater venous return, greater CO
Incr in contractility shift Frank Starling curve ____
shift upward, increasing CO for any RA pressure or EDV
Diastolic/systolic pressure Curve is the relationship between ____
diastolic/systolic pressure and diastolic/systolic volume in the ventricle
LV cycle loop
1–> 2 (isovolumetric contraction)
1) LA fills LV with blood (~140 mL= EDV)
low LV pressure because muscle is relaxed
2) on excitation, LV contracts and ventricular pressure incr
Mitral valve closes (LV pressure > LA pressure)
Since no blood ejected from ventricle= isovolumetric
LV cycle loop
2–> 3 (ventricular ejection)
3) Aortic valve opens when LV pressure > aortic pressure
blood eject into aorta and LV volume decr
–> STROKE VOLUME (LV ejected)
4) volume leftover in LV = end systolic volume
How do you measure stroke volume
width of the Pressure volume loop
LV cycle loop
3 –> 4 (isovolumetric relaxation)
5) LV relaxes
Aortic valve closes because LV pressure < aortic pressure
6) since all valves closed, LV volume constant
LV cycle loop
4–> 1 (ventricular filling)
7) when LV pressure < LA pressure, mitral valve opens and LV fills
8) LV fills to 140 mL (end-diastolic volume)
Changes in LV cycle loop
Increased preload
INCR WIDTH OF P-V LOOP
Increased EDV (incr venous return b/c incr blood volume or decr venous capacitance)
incr Stroke volume (more blood ejected from LV)
Changes in LV cycle loop
Increased afterload
DECR WIDTH OF P-V LOOP
due to increased aortic pressure
so LV ejecting blood against higher P –> decr in stroke volume
increased end-systolic volume
Changes in LV cycle loop
Increased contractility
LV has greater tension during systole
incr stroke volume
decrease in end-systolic volume
