Starling Curve Flashcards
pressure work
work needed to move blood from low pressure veins to high pressure arteries. 99% of energy used (volume pressure work or external work)
kinetic energy of blood flow
work needed to accelerate blood to its ejection velocity 1% of total work ( can increase to 50% during aortic stenosis). proportional to mass of blood ejected times velocity of ejection.
work load of right heart
1/6 of left heart
stroke work output
amount of energy converted to work during each beat
minute work output
total energy converted to work per minute (stroke work x HR)
are within vol. pres. curve
proportional to net external work. since kinetic work is usually small can consider it the stroke work output of heart .
total energy
stroke work output plus potential energy
potential energy
additional work heart could do if it were able to contract enough to empty ventricle.
cardiac efficiency
ratio of energy that is converted to work vs total energy consumed. work output/ total energy used. rest is lost as heat
normal cardiac efficiency
20-25%. Heart failure can go as low as 5-10%
optimal filling of heart
120-170. after that get increase in diastolic pressure.
max pressure generation
250-300 mmHg (60-80 for RV)
EDV and EDP
120 mls. 5-7 mmHG
ESV AND ESP
50 MLS 2-3 mmHg
max CO
15L/min
factors affecting HR
para/sympathetic tone of heart
factors changing SV
intrinsic contractility (preload), afterload, extrinsic contractility
1 mmHg change in preload changes ventricular vol. by…
25 mls
1 mmHg change in afterload reduces SV by…
.5 ml
fiber cannot shorten as much with increased afterload because…
at end of systole the fibers have to support higher tension which requires longer end systolic length
increased contractility affect on graph
left movement of ESV/ESP relationship, same systolic pressure at lower systolic volume. increases slope of line
estimation of contactility based on slope of line
change in pressure/ change in volume
energy production from heart
70-90% from oxidative metabolism of fatty acids, 10-30% from lactate and glucose (fetal hearts use mostly lactate and glucose to make ATP)
myoglobin
heart protein that binds with O2 making it easier for heart to extract O2 (venous sat at 25%)
only way to increase o2 supply to heart
increase coronary blood flow
basal metabolism of heart
25% of overall o2 use. maintains active transport mechanisms in cell
muscle contraction o2 consumption
75% ATP use associated with cross bridges . sequestration of calcium
isovolumetric contraction
50% of overall O2 use larget consumer. o2 use related to afterload. related to tension not pressure
law of laplace
tension= pressure x radius reduction of preload will decrease o2 use
stroke work
volume x pressure. increases in pressure more costly than volume .
afterload vs preload. contractilty vs HR on O2 USE
AFTERLOAD AND CONTACTILITY HAVE GREATER EFFECT ON O2 USE
