Peripheral Vascular Disease

Question 1

How do flow, velocity, and pressure change in stenosis?

Answer 1

Flow and pressure are decreased.

Velocity (at least across the stenotic area) is increased.

Question 2

About what percentage of stenosis is required to significantly decrease flow and pressure? (at rest?)

Answer 2

75%

Question 3

What’s claudation?

Answer 3

Intermittent ischemic pain in a leg or arm due to atherosclerosis.

Question 4

What’s a very easy way to diagnosis peripheral artery disease (PAD) in a limb?

Answer 4

Measure blood pressures - if it’s decreased in a limb vs. other limbs (at a proportion of s PAD.

Question 5

What does a normal flow velocity waveform of arterial flow in a large peripheral artery (eg. femoral) look like?

Answer 5

Phasic -forward flow with backward reflection, then small forward flow - with each heart beat.

Question 6

Is monophasic low in a larger peripheral artery normal?

Answer 6

Nope, this monophasic velocity waveform is often seen distal to a site of stenosis.

Question 7

What’s the ankle-brachial index (ABI?

Answer 7

The relationship, proportionally, of ankle BP vs. arm BP. Pretty simple.

Question 8

Is it possible for ABI only to be abnormal with exertion?

Answer 8

Yes. A procedure analogous to a stress test can be done to see if ABI changes with exertion.

Question 9

2 main forms of treatment for PAD?

Answer 9

Exercise and stenting.

Exercise seems to work better…. (but a study showed stenting to produce better QoL…)

Question 10

What outcome of PAD are you trying to avoid?

At what ABI might this occur?

Answer 10

Critical limb ischemia (necrosis of the limb)

This can occur at ABIs less than 0.35.

Question 11

What’s the one artery that comes of the internal carotid a. before the brain?

Answer 11

The opthalmic artery.

Question 12

Why does resistance vary between the internal and external carotid arteries?

Answer 12

Resistance is kept low in the ICA so that blood flows more consistently to the brain from the common carotid, even in diastole.

Question 13

Is a cholesterol embolus in the retina concerning?

Answer 13

Yes, because that could have gone up to the brain…

It’s a sign of significant atherosclerosis that needs to be addressed.

Question 14

What sort of lesion causes subclavian steal syndrome, and where must that lesion be?
Why does the syndrome result from this?

Answer 14

Subclavian steno-obstruction.
Flow is altered such that blood is diverted to the subclavian at the expense of blood flow to the vertebral arteries.
Lack of vertebral blood flow -> dizziness, vertigo.
Arm ischemia -> claudication and rest pain.

Question 15

What are the criteria for “moderate” renal artery stenosis? (there are 3)

Answer 15

50-70% stenosis AND
> 20 mmHg peak translesional pressure difference
> 10 mmHg mean translesional pressure difference

(stenosis >70% is “severe”)

Question 16

What’s one physiological consequence of renal artery stenosis?

Answer 16

Decreased flow to kidney -> activation of RAAS -> increased BP, sodium retention etc.

Question 17

4 clinical consequences of renal artery stenosis?

Answer 17

HTN
Chronic kidney disease
End-stage renal disease
Kidney size reduced

Question 18

Does the celiac flow velocity change much with feeding?

Answer 18

Nope.

it has a low-resistance biphasic waveform

Question 19

Does the superior mesenteric artery flow velocity change much with feeding?

Answer 19

Yes.
Fasting waveform: triphasic, high resistance.
Post-prandia: increased velocity and flow

Question 20

3 groups of symptoms of chronic mesenteric ischemia?

Answer 20

Post-prandial abdominal pain
Weight loss (due to food aversion and malabsorption)
Nausea, vomiting, diarrhea, constipation.

Question 21

Review: Why does Laplace’s law say large aneurysms are more likely to burst?

Answer 21

Large diameters require greater wall tension for a given amount of pressure.

Question 22

Can DVTs mess up valves?

Answer 22

Yes.

Question 23

Can DVTs be seen on echo?

Answer 23

Yes.

floating tips are thought to be bad

Question 24

How does the venous flow velocity waveform change in DVT?

Answer 24

the normal pulsatile pattern is replaced by abnormally continuous flow