Venous Return/ PV Loop Flashcards
Frank starling relationship
An increase in preload increases SV
The cardiac response to changes in venous return depends on __ and doesnt depend on ____
Dependent on intrinsic function
Not dependent on extrinsic neurohumoral mechanisms
Frank starling graph
Normal is an s
Low CO is lower- high afterload or decreased inotropy
High line is decreased afterload or increased inotropy
Non venous blood reservoirs
Heart
Lungs
Specific Reservoirs
Spleen
Liver
Large abdominal veins
Venous plexus beneath the skin largely controls via temperature
2 things that effect MCFP (mean circulating filling pressure)
Total blood volume
Compliance of the circulatory system
Because most blood is in venous system, venous compliance has a greater impact
Venous return- decrease vs increase from resistance change
Increase height by decrease in resistance
Decrease height by increase in resistance
Venous return- decrease vs increase from blood volume change
Graph shifts up or down
Up with more bv
Down with less bv
Venous return graph
straight, then downslope
Moves up and down (parallel) for volume change
Moves up and down (not parallel) but same end point for change in resistance
Why isnt frank starling parallel?
Bc no volume is added, only a change in pressure
MCFP
Mean circulating filling pressure
The pressure when cardiac output is 0
Arterial pressure drops
Venous pressure rises until there is no more flow
Pressure is steady until CO is 0, then it downslopes
VP loop
ACAO
MOMC
right and top- systole/ejection
left and bottom- diastole/ refilling
Ventricular Pressure volume loop determining SV
MC-MO
Each line of ventricular pressure volume loop
L isovolemic relaxation
B diastolic refilling
R isovolemic contraction
T ejections
What does ESV AC on PVL indicate?
inotropy
Further up and left- increased inotropy
Further in and right- decreased inotropy
Decreased EDV causes what to PVL
Makes it skinny by moving r line to the left
Decreased preload
Increased preload does what to LV pressure loop
widens square to the right
How does increased contractility / inotropy effect LV loop?
Increases height and decreases ESV (makes it taller and brings it to the left)
How does decreased contractility effect LV pressure loop
Shorter, higher ESV
moves in and to the right
How does an increase in afterload effect LV pressure loop
Makes pressure go high, but esv doesnt increase like in increased inotropy, esv actually is higher
Taller and skinnier
Decreased afterload in LV pressure loop
Shorter (less pressure from svr), lower esv (gets more blood out of heart bc low pressure to overcome)
Makes it a small little chubby graph
Aortic regurg vs mitral regurg on LV pressure loop
Unsure how to differentiate
Circle blob tall bc
Short blob
Aortic stenosis on LV pressure loop
Cause super high pressure, tall and skinny, high afterload
What is the cardiac function curve?
Frank starling curve
What will increase/ decrease the cardiac function curve?
Increase- decreased afterload or increased inotropy
Decrease- increased afterload or decreased inotropy
Volume/ pressure curve for veins vs arteries
Veins require more volume before they creat a pressure
Arteries create a higher max pressure, and start to create a pressure at lower volumes
What is unstressed volume
The amount of blood in a vein before it creates a pressure
When is unstressed volume decreased?
During hypovolemic states as an attempt to vasoconstrict and increase blood pressure
What is stressed volume
The amount of blood that participates in pressure generation
What can increase Venous return graph parallel vs not parallel
Parallel increase: increased blood volume or decreased venous compliance/ venous constriction
Not parallel increase: Decreased SVR/ arteriolar dilation
What is the PV loop useful for?
Assessing preload, afterload, and inotropy
When is MC pushed to left AND up? Examples?
NOT decreased preload!
During diastolic dysfunction
Chronic htn
Coronary heart disease
Aging
Aortic stenosis
Hypertrophic CMP
Restrictive CMP
How does a decrease in preload affect PV loop?
Shift to the left, also makes loop smaller
espvr reps
inotropy
PV loop acute and chronic HF
Inotropy keeps getting less steep
Graph just keeps shifting right
PV loop aortic regurgitation
Shifted to the right, a blob
Major huge R shift EDV bc the ventricle is getting hella fluid from RA and atrium
PV loop mitral regurg
Like AR but ESV is lower bc it pushes more out bc the floppy mitral valve, so it actually increases SV more than AV but not truly bc that blood is going to RA
