Vascular 101 Ms Mac Exam 2 review

What are the 8 branches of the ECA?

1) superior thyroid

2) ascending pharyngeal artery

3) lingual artery

4) facial artery

5) Occipital artery

6) posterior auricular artery

7) maxillary artery

8) superficial temporal artery

Doppler

Evaluation of the presence, velocity (speed), direction and character of blood flow within the vessels

For the CCA and vertebral artery, box is steered to the

right

Beam steering

-steer the color doppler beam in the direction of the vessel

What happens if box is not properly steered?

Color will not fill the lumen of the vessel properly and it could be mistaken for plaque or an occlusion

Keep the box small if

A higher color frame rate is desired

Pulsed Repetition Frequency color scale (PRF)

- controls PRF scale of the color velocity limits

High velocity flow needs

higher PRF/Scale

*and other way around *

If PRF is set too high

Color will not fill the vessel

If PRF is set too low...

color will wrap around vessel (Alias)

What color should be on top of the color bar when the box is steered to the right?

red

What color should be on top of the color bar when the box is steered to the left?

blue

Sample volume gate (SVG)

Represents the area of flow assessed with Doppler

*placed mid stream

* set between 1.5 and 2mm

Steer Doppler angle cursor

controls the angle of the sample volume

what degree is the steer Doppler angle supposed to be set at?

45-60°

When dopplering in our lab class at what angle is the steer Doppler supposed to be at?

60°

Steer beam

Steer will control the direction of your Doppler cursor, Doppler beam line and color box

The steer beam should always be in the

Same direction as your color box and vessel

Doppler effect

Observed frequency change of reflected sound due to reflector movement relative to the sound source of the observer

Doppler shift

mode used to detect blood flow.

Do RBCs emit sound?

No, its considered a moving reflector

We rely on our transducers to

Send sound and recieve thd echo from moving reflectors

If the returning frequency is higher, the Doppler shift is positive. This is known as.

Antegrade flow

If the returning frequency is lower than the transmitted frequency, the Doppler shift is considered a negative shift. This is known as

Retrograde flow

On the Doppler display, the machine plots

Velocity (Y axis shown in CM) over time (X axis)

Puse Repetition Frequency (PRF)

Number of pulse echo cycles occurring in one second

(Hz)

Aliasing/Nyquist Limit

the wrapping around of the spectral waveform that can result from high velocity of blood flow-nyquist limit is exceeded

*try adjusting the baseline and then increase PRF scale to correct*

When does aliasing occur?

When the Doppler shift frequencies exceed 1/2 of the PRF (Nyquist limit)

Pulsed wave Doppler

uses a single element transducer that emits brief pulses of ultrasound energy

PW advantage

Ability to measure velocities at a specific location (range resolution)

PW disadvantage

Aliasing of velocities: inability to measure high velocities accurately.

CW Doppler

allows us to measure blood velocities along an entire line of interrogation

CW advantage

measures high velocities', no aliasing

CW disadvantage

not site specific, lacks range resolution (range ambiguity)

sweep speed

This switch changes the speed of the spectral display

dicrotic notch

represents the closure of the aortic valve and the onset of diastole

Acceleration

The systolic upstroke when the AOV opens and blood enters the carotid

CCA waveform characteristics

-Sharp upstroke and Peak

-Well defined dicrotic notch

-Diastolic flow

-Low Resistance

*color flow will reveal a lighter shade of red during systole and a darker shade of red during diastole*

Which vessels have a low resistance waveforms?

CCA, ICA, Vertebral, renal, splenic and hepatic arteries

High resistance waveform

This waveform is characterized by a sharp rise in flow velocity during systole, a rapid decline toward the baseline, and diminished diastolic flow

Which arteries have high resistance waveforms?

ECA, aorta, subclavian, extremity arteries

What's the normal peak systolic velocity of the CCA?

Less than 125cm/sec (

What's the normal vertebral artery peak systolic velocity?

20-60cm/sec in most pts

The vertebral artery

- Supplies blood to the posterior brain

- flow is antegrade

- low resistance vessel

What is the normal peak systolic velocity for ICA?

Less than 189cm/sec

What's the normal PSV in ECAs?

Less than 200c

Which vessels have a dicrotic notch?

ECA, CCA

What are some characteristics of the ECA?

- A lighter shade of red will be seen during systole. The normal color flow pattern will decrease during diastole and may disappear at the end diastole (no flow - flashes)

- more pulsatile Doppler signal

- flow pattern is a characteristic of flow patterns seen in high resistance distal vascular beds such as the face and scalp

ECA spectral waveform will oscillate with...

temporal tap

How to obtain the ECA and ICA?

Transducer is moved slightly anteriorly and posteriorly

Arteries and veins are both made up of what three layers?

Tunica intima: innermost layer

Tunica media: middle layer

Tunica adventita: Outer layer

The íntima of an artery is in contact with

Moving blood flow

The media of an artery is

The muscular layer that consists mostly of smooth muscle cells and allows rhythmic changes in the arterial size during cardiac cycle

Where is elastin and collagen found?

Media of an artery

What layer of the artery contains vasa vasorum?

adventitial layer

Large arteries

Elastic arteries with less smooth muscle, aorta and its largest branches

Small arteries

Approx 4mm in diameter, well developed smooth muscle layers. Include all arteries EXCEPT aorta and major branches

Arterioles

- smallest arteries

- Known as "stopcocks" of the vascular system

- circular smooth muscle layers control contraction and resistance

Capillaries

- Smallest blood vessels

- Place where nutrient exchange occurs

Venules

smallest veins

Small veins

1-10mm in diameter

- all veins EXCEPT portal vein, vena cava and their main branches

- walls are mainly connective tissue

large veins

- portal vein, vena cava and its branches

- thick adventitial layer w fibrous and elastic tissues

Veins

- thinner walls

- same laminate structures as artery but not as muscular

- have more elastic fibers and collagen than muscle fibers

Which vessels have valves?

veins

What's the purpose of venous valves?

Prevents retrograde movement of blood

systemic circulation pathway

Blood leaves the LV:

Aorta, arteries, arterioles, capillaries, venules, veins, and vena cava to enter the RA of the heart

Hemodynamics

the study of blood moving through the circulatory system

Laminar flow

normal blood flow

- consists of many laminae (layers)

- blood layers slide concentric

Disturbed flow

occurs when the parallel stream lines are disturbed (at the bifurcation)

Flow Separation

occurs when there is a sudden widening of a tube or vessel which causes the flow to reverse along the walls (at the bulb)

- known as the boundary layer

Turbulent flow

an irregular, mixing flow patter usually due to pathology in the artery

-occurs distal to a stenosis in a vessel

Plug flow

occurs when all of the layers and blood cells travel at the same velocity

- known as blunt flow

- occurs at branching origins and proximal to stenosis

Turbulent flow is characterized by

- chaotic flow patterns in many different directions and at many speeds

- often associated with pathologies and increased blood velocity, and beyond a stenosis

- spectral broadening on wave form

- May have a feathered appearance on wave form

Eddy currents or random vortices

appear as small hurricane like swirling rotational patterns

Proximal to a stenosis

velocity and pressure are baseline

Within the stenosis

velocity is high and pressure is low

Immediately distal to the stenosis

velocity will begin to decrease again and pressure will rise higher than in the stenosis

Tardus Parvus

a waveform of low amplitude and delayed rise to systole

When does turbulent flow occur?

When Reynold's number is greater than 2000

An increase in flow speed

Increases Reynolds number

Reynolds number (Re)

RE= (average flow x density x tube diameter) / viscosity

Bernoulli's Principle

describes the relationship between area, velocity, and pressure at a stenosis

When there is high velocity

There is low pressure

When there is low velocity

There is high pressure

Examples of Bernoulli's Principle

Areas of flow separation and stenotic (narrowed) vessels

Velocity and pressure share an

Inverse relationships

Pressure gradient

Pressure difference between two points

*there must be a pressure gradient present for flow to move*

What elements will flow from a higher pressure to a lower pressure?

Blood, air, and gas

Blood will move from an area of ___________ pressure to an area of ___________ pressure

higher, lower

Poiseuille's Law

describes the relationship between resistance, pressure, and volume flow

*gives insight into the complex task of regulation blood flow to different parts of the body*

Vasodilation by 19% will

double the blood flow

Vasoconstriction by 16% will

cut blood flow in half

The process of vasodilation and vasoconstriction offer

Powerful control mechanisms

Resistance to flow

-Due to changes in size of vessels (length & diameter).

-Influenced by length of tube, viscosity and radius (primary influence).

Collateral blood flow

heart makes new branches of blood vessels as we age so that damaged areas of the heart get good blood flow