Arterial Vascular Hemodynamics Flashcards
____ describes Normal situation in arterial system
Pressure gradient between heart and venous system
Heart pump creates alternating high pressure states, “pulses” (Systole – left ventricular contraction, high pressure and Diastole – left ventricular relaxation, low pressure)
pulsatile flow
acceleration =
deceleration =
flow speed increasing, systole
flow speed decreasing, diastole
_____ is the Characteristic of vessel to Expand during systole and Contract during diastole
Your “pulse” felt
Help to maintain flow in diastole
Known as Windkessel effect
Effect lost with atherosclerosis – “hard” or stiff vessel wall
compliance
the ____ effect can result in
Continued forward flow
Flow reversal
Windkessel
______ is Dependant on vascular resistance downstream
Low resistance – continued flow
High resistance – flow reversal
compliance
______ determine vascular resistance
how?
distal arterioles
Vasoconstricted – higher resistance b/c smaller diameter
Vasodilated – lower resistance b/c larger diameter
Vessels of your face are ____ “at rest”, your normal state
Flow in the vessels would be high resistance
Vessels of your face ______ with emotional stress, when you are embarrasses and you “blush”
Flow in the vessels would be low resistance
vasoconstricted
vasodilate
what is the difference in these 2 waveforms?
lt is high resistance w/ little diastolic flow
rt is low resistance w/ a lot of disatolic flow
tissues demand for blood varies by tissue type.
what do muscles require?
how about organs?
what is flow state dependent upon?
Generally muscles at rest require less blood – High resistance, Flow only in systole
Examples – legs, arms, face
Generally organs need continuous supply of blood - Low resistance, Flow in systole and diastole
Examples – kidneys, brain, liver
Flow states can change based on tissue demand in normal situations or with pathology
the below are examples of _____
Peripheral arteries at rest; Upper and lower extremities, Face (ECA)
Organs at “rest”
SMA when fasting
Ovarian artery to non- dominant ovary
Nongravid uterus
What are its Flow characteristics?
high resistance
Diastolic reversal
“triphasic”
when would high resistance change to low?
Peripheral arteries will vasodilated with abnormal and normal situations: Smoking, exercise, Body heating
Emotional reaction - autoregulation
Induced hyperemia with inflated blood pressure cuff
Distal to stenosis
Organs that are not working are in ____ resistance?
e.g.
high
SMA (feeding the bowel) in a fasting state
Ovarian artery feeding a non-dominant ovary
Uterine artery feeding a non-gravid uterus
when organs are working they require ___ blood so they go to ___ resistance
e.g.
what happens to diastolic flow at this time?
more, low
SMA post prandial
Ovarian artery feeding a dominant ovary
Uterine artery during pregnancy
it increases
most organs require ____ blood and stay in ___ resistance?
e.g.
continuous, low
Brain (ICA)
Kidneys
Liver
flow changes to organs that require continuous blood indicates _____
e.g
this change to high resistance may be a result of (3)
pathology
For example, it is NEVER normal for a kidney to be high resistance
Changes to organ parenchyma from disease
Distal stenosis
Poor cardiac perfusion
_____ has dramatic effect on flow in the arterial system
Determines the volume of blood entering the system
Determines the pressure
cardiac status
poor cardiac otput can be caused by (3) …
abnormal flow is result os (2) …
Congestive heart failure
Aortic valve stenosis
Coarctation of aorta
Slow acceleration
Lower velocity
what does the continuity rule say?
what is the volume calculation?
The volume of flow through a stenosis remains constant:
Blood not lost
Whatever comes into stenosis must go out
(volume calculation) Q = Vessel Area x Average Velocity
Area = 3.14r2
Average Velocity – measured over one cardiac cycle
with a focal stenosis the velocity will ___ to ______.
increase, maintain volume of flow
to maintain volume, if diameter decreses, ___ must _____
velocity, increase
Think of a garden hose – if you cover ½ the hole at the end the water comes out faster….
You’ve decreased the AREA of the tube so the flow is FASTER to maintain the same VOLUME of flow!
what happens after a stenosis?
Velocity decreases after stenosis
Vessel widens – increasing the area
Turbulence of flow develops
Bruit can be heard with a stethoscope
____ describes relationship between pressure gradient and velocity, the preservation of energy (Potential, Kinetic)
and says that as kinetic energy increases (velocity), potential energy decreases (pressure)
Bernoulli Effect
based upon the Bernoulli Effect, at stenosis, pressure ___ and velocity ____.
how is this predicted?
decreases, increases
this is a predicatable relationship –> P1 -P2 = 4 V2
Knowing the proximal pressure (P1)
Use Doppler to measure the velocity
Calculate the distal pressure (P2)
based on this…
you can say…
Systole
Acceleration (aka) Acceleration time
Rise time
upstroke
Peak velocity
Diastole
Dicrotic notch
Diastolic flow
End diastolic velocity
the below describe what?
Vessel area is slightly reduced
Flow velocity is slightly increased
No pressure drop
Little to no turbulence
mild stenosis
the below describes what?
Vessel area is severely reduced
Flow velocity increases 2-3 x
Pressure drop distal to stenosis
Post stenotic turbulence
servere stenosis
what can you tell based upon this?
what the pressure gradient is. P1 -P2 = 4V2
If the pressure is 120 mmHg proximal to stenosis, the pressure will be 104 mmHg distal to stenosis)
_____ will result in ____ velocity through the stenosis in attempt to _____ flow volume. There will be a pressure ____ distal to disease, because much of the energy is ____ to heat upon exiting of the stenosis.
Significant disease, increased, maintain, drop, lost
___ % greater diameter stenosis is “hemodynamically significant”
what are the variables that affect this?
60
* Length of stenosis
* Flow volume
what does this show?
Velocity proximal to the stenosis is 51 cm/s
what does this show?
Velocity in the stenosis is 467.9 cm/s
This is an increase in velocity of 9x!!!! (from below image)
The pressure gradient is 4(4.6 m/s)2 = 85 mmHg. This is a critical stenosis.
____ results from pressure changes within the vessel
Causes the flow to come turbulent
This happens anywhere the vessel widens
Happens after a stenosis when vessel widens – Some natural ares of widening, i.e. carotid bulb
flow separation
this demonstarted ____ stenosis b/c _____
mild, arterioles downstream unchanged in diameter, still vasoconstricted
this demonstartes ___ senosis b/c ____
moderate, Arterioles dilated, creating lower resistance flow
image below: Rt CFA distal to
severe aortic stenosis
this demonstrates ___ disease b/c ____
severe disease, Arterioles very dilated,
creating lower resistance flow
below: Left SFA occlusion,
no iliac disease
this demonstrates ___ disease b/c ____
very severe, Insufficient diastolic pressure to maintain flow
Arterioles very dilated but not receiving flow
Proximal to stenosis:
normal acceleration time
decrease diastolic flow
very high resistance
At the stenosis:
increased velocity
Distal to stenosis:
turbulence
Lower velocity
Slow upstroke
Increased diastolic flow
