Taylor- Cardiac Output Flashcards
3 ways the body can alter stroke volume
contractility, aortic pressure, venous pressure
cardiac output of the heart=
stroke volume x HR
cardiac output of vasculature=
MAP/SVR
increasing volume increases _____ of contraction
strength (Starling’s law)
A, B, C, D
ejection loop
A: diastolic filling
B: isovolumetric contraction
C: ejection
D: isovolumetric relaxation
ejection fraction=
SV/LVEDV
normal ejection fraction
above 0.50
real ejection loop has rounded top since bp changes during ejection
auxotonic beat
increased contractility does what to stroke volume; what about LVESV
increases it (can eject more blood out); LVESV is lower
decreasing contractility does what to SV and LVESV
decreases SV; LVESV is higher (less blood ejected)
raising aortic pressure does what to emptying of the heart (increases afterload)
opposes emptying of the heart
increasing aortic pressure does what to SV and LVESV
SV decreases; LVESV higher (can’t empty contents of heart well)
lowering aortic pressure (reducing afterload) allows ventricle to do what
empty more completely
decreasing aortic pressure does what to SV and LVESV
increases SV; LVESV lower
increasing venous pressure does what to SV and LVEDV
increases SV; LVEDV is higher (increased preload)
decreasing venous pressure does what to SV and LVEDV
SV lower; LVEDV lower
how much arterial pressure the heart works against during systole
afterload
how hard the heart contracts during systole
contractility
how much blood fills the heart from venous side during diastole
preload
fundamental determinant of stroke volume and cardiac output; determines preload
central venous pressure
what happens to LVEDV and SV when ventricular hypertrophy is present
LVEDV decreased due to reduced diastolic compliance; SV decreases
what happens at high HR’s to CO and why
decreases; less filling time b/t beats
why does CO increase with increasing HR during EXERCISE
sympathetics speed up both contraction and relaxation (more diastolic filling time)
what happens if heart is
NOT pumping
no flow and bp constant at 7mmHg
heart and circulation relationship
interdependent
heart SV increased, venous pressure would ____ in response
decrease; heart pulling more blood out from venous side reducing venous pressure
increase volume and pressure provides more ____ to the heart and the more you get out
load
meaning of this
only 1 cardiac output and venous pressure that can satisfy the system (it’s self-correcting)
3 things that can alter cardiac output
contractility
venous tone or blood volume
arteriolar tone (SVR)
increasing contractility will do what to CO and venous pressure
CO will increase; venous pressure will fall
decreasing contractility does what to CO and venous pressure
CO decreases; venous pressure increases
one of the reasons venous pressure rises in heart failure
contractility decreased and CO decreased
increasing blood volume (hypervolemia) will do what to CO
CO increases
decreased blood volume will do what to CO
CO decreases
best guide for adjusting blood volume in patients
venous pressure
venous constriction does what to CO
CO increases
venous dilation does what to CO
CO decreases
if the heart is stopped, increasing or decreasing resistance has what effect on CO
no effect
when the heart is pumping, increasing resistance has what effect on arterial and venous pressure
raise arterial (upstream) and lower venous (downstream)
decreasing arteriolar tone (SVR) does what to aortic pressure and SV and CO
aortic pressure decreases
SV increases
CO increases
increasing arteriolar tone (SVR) will have what effect on CO
CO decreases
exercise’s effect on CO
increased CO
2 main things that happen during exercise that increase CO
high sympathetic drive (increase contractility and venoconstriction)
arteriolar dilation in active muscle
ACTIVE HYPEREMIA
reduced contractility of heart increases_____ and lowers ______ in heart failure
venous pressure
CO
during heart failure w/ poor perfusion, body will retain fluid and _____ blood volume (restoring CO but further raising venous pressure); what is this called
increases; compensated heart failure
main cause of elevated venous pressure in heart failure
fluid retention
contractility of heart continues to degrade and can’t restore CO; venous pressure rises until edema occurs
congestive heart failure
