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Vasculature > Week 3 - Lesson 1 (Part 8) > Flashcards

Week 3 - Lesson 1 (Part 8) Flashcards

1
Q

What does biphasic flow indicate if seen in a vessel supplying a high resistance bed?

A

Indicates mild disease

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2
Q

How does a biphasic flow wave appear sonographically? (3)

A
  1. High pulsatility
    - not as much as triphasic
  2. High resistance
  3. 2 points
    - one above and one below the baseline
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3
Q

What happens to the walls during biphasic?

A

They start to become stiff and rigid

- start to see some changes

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4
Q

How does a monophasic flow wave appear sonographically? (3)

A
  1. Flow is all above the baseline
  2. Low pulsatility
  3. Low resistance
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5
Q

What are examples of low resistance? (6)

A
  1. Vertebral arteries
  2. Brain
  3. Distal ICA
  4. Ovaries
  5. Testicles
  6. Kidneys
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6
Q

What is working hard during digestion?

A

SMA

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7
Q

What kind of flow is monophasic? (2)

A
  1. Continuous flow

2. Low resistance

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8
Q

When is monophasic seen abnormal?

A

If seen in a vessel supplying a high resistant bed

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9
Q

Critical stenosis

A

Encroachment on the lumen of an artery by an arteriosclerotic plaque can result in diminished pressure and flow distal to the lesion

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10
Q

Why does encroachment on the lumen have to be relatively extensive before hemodynamic changes are manifested?

A

Because large arteries offer little resistance to flow compared to smaller distal arteries

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11
Q

What are factors that determine the stenosis effect? (7)

A
  1. Length and diameter of the narrowed segment
  2. Roughness of the epithelial surface
  3. Degree of irregularity of the narrowing and its shape
  4. Ratio of the cross-sectional area of the stenotic zone to that of the normal vessel
  5. The rate of flow
  6. The arteriovenous pressure gradient
  7. Peripheral resistance beyond the stenosis
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12
Q

What is the most important factor determining the stenosis effect?

A

Diameter

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13
Q

Tandem lesion

A

One stenotic lesion after another, after another

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14
Q

What is important to recognize about tandem lesions?

A

That two or more stenotic lesions that occur in series have a more pronounced effect on distal pressure and blood flow than does a single lesion of equal total length

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15
Q

What is the result of tandem lesions?

A

Is large losses of energy at the entrance and particularly at the exit of the lesion

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16
Q

What kind of flow patterns do tandem lesions have?

A

Disturbed

- jets, turbulence and eddy formation

17
Q

What happens to the total blood flow to an extremity during a severe stenosis?

A

It can remain normal

18
Q

Why can total blood flow to an extremity during a severe stenosis remain normal?

A

Because of the development of collateral circulation as well as a compensatory decrease in the peripheral resistance

19
Q

What is a better method of assessing the presence and severity of the occlusive disease?

A

Measurement of systolic pressure

- listening to blood flow is very important

20
Q

Where does blood flow appear to have a higher resistance pattern?

A

Proximal to a critical stenosis or occlusion

- due to the pressure drop across the stenosis

21
Q

When does flow reversal disappear?

A

Distal to a stenosis

22
Q

What kind of waveform does doppler have?

A

Single component

- monophasic

23
Q

When does the monophasic signal only occur?

A

During systole

24
Q

What are the factors that contribute to the disappearance of reversed flow distal to the stenosis? (4)

A
  1. The maintenance of a relatively high level of forward flow throughout the cardiac cycle
  2. Resistance to reverse flow created by the stenotic lesion
  3. A decrease in peripheral resistance as a result of ischemia
  4. Damping of the pressure wave by the lesion,resulting in attenuated pressure pulses
25
Q

What is the normal blood flow of arteries? (2)

A
  1. Blood flow velocity increases rapidly to a peak during early systole
  2. Decreases during early diastole when flow reversal can occur
26
Q

What does the shape of the resulting pulse velocity wave reflect on?

A

The pressure gradient

27
Q

How many sounds are heard over normal peripheral arteries?

A

Double or triple sounds

28
Q

What is the second sound that is heard over normal peripheral arteries?

A

Diastolic flow reversal

- biphasic

29
Q

What is the third sound that is heard over normal peripheral arteries?

A

Second forward component

- triphasic

30
Q

What is doppler spectrum critically related to?

A

The detailed variation of velocity within the vessel of interest

31
Q

What does the velocity of blood depend on?

A

Its position within the vessel

- this is the velocity profile

32
Q

What does steady laminar flow demonstrate?

A

A parabolic velocity profile as seen in a long straight tube

- eg. CCA

33
Q

Where is max velocity of a blood vessel?

A

In the centre

34
Q

Where is min velocity of a blood vessel?

A

By the periphery

- walls

Vasculature (45 decks)

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