Final Flashcards
In Poiseuille’s Law, what is the most important variable?
Radius (r), as it is to the 4th power
Does Hunter’s canal (mid thigh) have a high or low incidence of atherosclerosis?
High.
What is the cause of a greater ankle pressure than brachial pressure? Is it normal?
Systolic amplification is due to increasing arterial stiffness in smaller vessels, and is normal.
Normal waveform for legs and arms at rest?
Triphasic
How is hemodynamically significant defined?
As a drop in pressure and flow.
What is the most important factor influencing the severity of an obstruction: diameter, length, or degree of irregularity?
Diameter.
Where is the greatest energy loss, before or after a stenosis?
After - exit losses due to turbulence.
How does circulation change as a stenosis develops?
Relaxin released, which dilates vessel.
Collaterals develop.
Peripheral runoff beds dilate to reduce resistance.
What are the three components of collaterals?
Stem arteries (such as ECA, PFA) Midzone collaterals Re-entry vessels (frequently reversed).
What are causes of pulsatility in the lower extremities?
CHF
Tricuspid regurgitation.
Fluid Overload.
What technique can be used to demonstrate patency of the iliacs?
Valsalva maneuver - flow should stop during Valsalva, then resume afterward.
50% diameter reduction is what % area reduction?
75%
60% diameter reduction is what % area reduction?
90%
What is the 2 cm rule?
If proximal portion of AAA is ≥ 2 cm beyond SMA origin, renal arteries are probably not involved.
What resistive index criteria indicates parenchymal disease?
RI > 80
RI = (PSV - EDV)/PSV
How much larger than the rest of the vessel need to be to be considered aneurysmal?
1.5 times
What is the velocity criteria for SMA and Celiac for mesenteric ischemia?
SMA ≥ 275 cm/sec
Celiac ≥ 200 cm/sec
What is the 2 artery rule for mesenteric ischemia?
Two of the three splanchnic arteries need to be stenosed or occluded.
What are the criteria for portal hypertension? (6)
Flow < 15 cm/sec Portal vein diameter > 13 mm Splenomegaly > 13 cm Waveform to-fro or reversed Development of shunts Hepatofugal flow
What are the criteria for renal artery stenosis? (4)
Renal:Aorta velocity ratio > 3.5:1
PSV > 180 cm/sec
Acceleration time > 0.1
Loss of early systolic peak
Size criteria for aortic and iliac aneurysm?
Aorta: > 3 cm
Iliac: > 1.5 cm
After an exercise test, a pressure drop of what is considered diagnostic of PAD?
20 mmHg
For SLP, a drop of what in legs segments is considered significant? Arms?
Legs: 30 mmHg
Arms: 20 mmHg
At what ankle pressure does rest pain begin?
< 40 mmHg
List the four ABI levels for Normal, Claudication, Multi-level, and rest pain.
Normal: > .96
Claudication: < .8
Multi-level: < .5
Rest pain: < .3
When comparing ABI’s from earlier tests, or post exercise, what drop in ABI is considered significant?
0.15
At what velocity ratio is a stenosis considered hemodynamically significant?
2:1
What are the PSV and EDV velocity criteria for an 80-99% carotid stenosis?
PSV > 125
EDV > 100
