Arterial Physiology & Fluid Dynamics Flashcards
the arterial system pumps ~ ___ ml of blood into the aorta with every heartbeat
~70ml
what is stroke volume?
amount of blood ejected
blood moves from regions of ___ to ___ energy
high to low energy
what 3 types of energy are there in the vascular system?
kinetic
potential
gravitational
what is the formula for kinetic energy?
KE = 1/2mv²
what is the formula for potential energy?
PE = mgh
two types of laminar flow
parabolic flow
plug flow
describe parabolic flow
highest velocity is in the center of the lumen
describe plug flow
blood travels at the same velocity throughout the lumen
what is viscosity?
thickness of fluid
↑ viscosity causes ↓ ____
↑ viscosity ↓ velocity
___ of the vessel has an even more dramatic effect on flow resistance
diameter
what is the equation for flow resistance?
R = 8ηL / πr⁴
η = fluid viscosity
L = length
r = radius
what is the equation for Poiseuille’s Law?
Q = (P1 - P2)πr⁴ / 8ηL
P1 = pressure at the proximal end
P2 = pressure at the distal end
r = radius
η = fluid viscosity
L = length
what is the equation for Reynolds Number?
Re = Vp2r / η
V = velocity
r = radius
p = density of fluid
η = fluid viscosity
Re > 2000
turbulent flow
turbulent flow may cause the vessel walls to vibrate which is called a ___
bruit
what is Bernoulli’s Principle?
velocity and pressure are inversely related
flow separations are caused by changes in (2)
geometry of the vessel
direction of the vessel
flow seperations help define whether an image is in systole or diastole, during ___ the flow at the vessel wall is stagnant
diastole = stagnant
A = early systole
B = peak systole - aorta walls distend, storing PE
C = late systole - temporary flow reversal
D = early diastole
E = late diastole - vessels recoil, converting PE to KE
unilateral flow alterations suggest ___ and/or ___
vessel disease and/or extrinsic compression
bilateral flow alterations suggest ___
cardiac involvement
stenosis of the aortic valve causes (2)
delay in systolic upstroke
decrease PSVs
regurgitation/insufficiency of the aortic valve cause (2)
double systolic peak (pulsus bisferiens)
diminished diastolic flow or reverse flow
high cardiac output may be evident in ____
younger athletes
high cardiac output may be related to ___
noncardiac source (anemia)
low cardiac output
unilateral - suspect ___
bilateral - extreme case of ___
unilateral - suspect severe proximal occlusive disease
bilateral - extreme case of cardiomyopathy
intra-aortic balloon pump provides temporary assistance with left ventricular contraction by ___
decreasing afterload
intra-aortic balloon pump increases ___ in cases of low cardiac output or cardiac instability
increases coronary artery blood flow
intra-aortic balloon pump is placed in the thoracic aorta via ___
superficial artery
intra-aortic balloon pump is inflated during ___ which increases aortic pressure and coronary artery blood flow
diastole
intra-aortic balloon pump is deflated during ___
left ventricular ejection
ventricular assist device (VAD) assist weakened ventricles by ___
mechanically pumping blood out of the heart
what is LVAD?
continuous flow pump (most commonly used)
what is BiVAD?
pulsatile flow pump that assists both ventricles
what is the most common finding suggestive of a cardiac abnormality?
pulsatile venous Doppler in the lower extremity
what is the best vasodilator of high resistance vessels?
exercise
exercise decreases ___ of the Doppler signal
decreases flow reversal
stenosis causes a major reduction in (2)
volume flow
pressure
stenosis is significant when the cross-sectional area of the arterial lumen is reduced ___% which corresponds to a diameter reduction of ___%
cross-sectional area reduction 75% = diameter reduction 50%
true or false: 2 or more stenotic lesions that occur in series have a greater effect on volume flow and distal pressure than a single lesion of equal total length
true
if there are stenoses in two different. vessels that are parallel, the overall resistance to flow is ___ than the resistance in each individual stenosis
less
velocities usually dampen ___ to stenosis
proximal
the increased range of Doppler frequency shift frequencies is displayed as ___
spectral broadening
___ turbulence is usually seen with stenosis
poststenotic turbulence
