Peripheral vascular disease and physiology

Question 1

Blood flow to hand at rest vs exercise

Answer 1

-at rest: low and mostly during systole -exercise: both systolic and diastolic flow increase providing needed oxygenated blood to meet increasing metabolic demands

Question 2

Bernoulli’s Principle states that the the _______ of a moving fluid increases, the _______ within the fluid decreases

Answer 2

-speed -pressure

Question 3

As stenosis severity increases, the blood velocity ______, at approximately 75% stenosis, the flow _______ and the pressure _________.

Answer 3

-velocity increases -flow decreases -pressure decreases downstream

Question 4

3 vascular physiology principles

Answer 4

-diastolic flow is important to maintain adequate tissue perfusion -an increase in blood velocity (NOT FLOW) occurs at a stenosis -at 75% stenosis, flow and P decrease

Question 5

5 areas of artery obstruction discussed

Answer 5

-lower extremity: intermittent claudication -carotid -vertebral -renal -mesenteric

Question 6

Ankle Brachial Index

Answer 6

The ankle-brachial index can indicate health or impairment of arterial function in the lower extremities, aiding in the diagnosis of PAD. The schematic diagram presents a guide to the determination of a patient’s ABI. The index is the systolic blood pressure at the ankle divided by the brachial systolic blood pressure using which ever (PT or DP pressure is higher). brachial p used is whichever is higher, even if not equal on both sides of the body

Question 7

Normal vs abnormal ankle brachial index

Answer 7

-above .91 is normal 0.71-0.9 is mild impairment 0.41-0.70 is moderate impairment 0-0.40 is severe impairment!

Question 8

Stenosis vs Nonstenosis ultrasound velocity signal in femoral artery

Answer 8

-normally: triphasic forward, backward, forward -stenosis: monophasic waveform at really high velocity to try to maintain flow

Question 9

How might a physician tell if there is a borderline block in a patient’s femoral artery?

Answer 9

-fine at rest but if you see ankle brachial index decrease after exercise in pt

Question 10

Therapy for PAD

Answer 10

-exercise!! despite getting intermittent claudication, it is more beneficial in the long run

Question 11

CLEVER study results: patients with claudication due to hemodynamically significant aortoiliac disease randomized to either optimal medical care or stent revasc. or supervised exercise

Answer 11

-pts with mdoerate to severe claudication due to aortoiliac disease benefited the most in treadmill walking time by being on the exercise program, even 18 mos later! -but stenting was associated with the largest increase in QOL

Question 12

Critical limb ischemia

Answer 12

-results when the blood flow to the legs does not meet the metabolic demands of the tissue -this typically occurs when the ABI is <0.35 -pts frequently develop night pain and lay the leg over the edge of the bed to get relief -blood flow restoration is needed for limb salvage!!

Question 13

Approx. 1/3 of strokes are caused by what?

Answer 13

-emboli from atherosclerotic plaque in the carotid or aortic arch -can also come from heart due to other conditions like a fib

Question 14

The internal carotid artery feeds into the ________ in the brain. It’s only branch before this is the ___________. The external carotid artery supplies blood to the face.

Answer 14

-MCA -ophthalmic artery

Question 15

The common carotid artery waveform is a combination of the ICA and ECA waveforms. Describe these two.

Answer 15

-ICA: relatively low resistance signal (higher diastolic velocity) whereas ECA had high resistance with less diastolic velocity -the lower resistance flow in the ICA ensure adequate blood flow to the brain

Question 16

Hollenhorst plaque

Answer 16

-cholesterol embolus from ICA shown in retina due to ophthalmic branch

Question 17

If a physicians seens a bright, refractile, yellow plaque in a blood vessel within the eye, what are they thinking this is clinically?

Answer 17

-Hollenhorst plaque: cholesterol embolus seen in BV of the retina -caused by an embolus lodged within the retinal vessel that originated from an athermatous plaque is a more proximal vessel, usually the ICA -sign of severe atherosclerosis

Question 18

Subclavian Steal Syndrome cause

Answer 18

-Subclavian steno-occlusive disease produces neurologic symptoms when compensatory flow to the subclavian artery from the vertebral artery diverts too much flow toward the arm and away from intracranial structures. The quality of collateral blood supply and the capacity to increase collateral flow to the intracranial circulation (brainstem in particular) may be the principle determinant as to which patient develops neurologic symptomatology.

Question 19

Subclavian Steal Syndrome symptoms

Answer 19

-symptoms that occur (dizziness, vertigo) are most typically related to vertebro-basilar and posterior cerebral circulation ischemia -arm ischemia occurs, causing arm claudication and rest pain

Question 20

Renal Artery Stenosis Anatomical Criteria

Answer 20

-moderate lesion: 50-70% stenosis AND >/ 20mmHg peak translesional gradient, >/10 mmHg mean translesional gradient -severe lesion: >70% stenosis

Question 21

Renal Artery Duplex waveform indicating high grade stenosis

Answer 21

-A significant stenosis in the renal artery results in both increased systolic and diastolic blood velocities (220 cm/sec when usually 20-30) -increased diastolic as well to maintain flow to kidney

Question 22

Why is renal artery stenosis always seen in a hypertensive patient?

Answer 22

-RAS causes activation if the RAAS which causes HTN -called renovascular HTN -The result is profound angiotensin-mediated vasoconstriction and aldosterone-induced sodium and water retention. In the 2-kidney 1-clip model, where the clinical correlate is unilateral renal artery disease, sodium and water handling via pressure diuresis of the contralateral kidney may be sufficient to prevent a volume component to the hypertension. In the setting of a solitary kidney (experimentally, the 1-kidney 1-clip model), sodium and water handling is compromised, sodium and water retention ensues, and volume-mediated hypertension occurs.In unilateral

Question 23

Clinical consequences of Atherosclerotic renal artery stenosis

Answer 23

• hypertension
• chronic kidney disease
• end-stage renal disease
• kidney size is reduced in response to critical stenosis

Question 24

Celiac vs SMA artery blood flow waveform

Answer 24

• celiac: biphasic, low resistance, little change with meal
• SMA: triphasic, high resistance fasting waveform that increases in PSV and EDV (velocities) significantly with a meal!

Question 25

Clinical presentation of chronic mesenteric ischemia

Answer 25

• postprandial abdominal pain
• weight loss: “food fear”, malabsorption
• nausea, vomiting, diarrhea, and constipation

Question 26

Rupture risk of an aneurysm and diameter, which famous old guy do we have to thank for this?

Answer 26

• higher the diameter, higher the rupture risk
• La Place: T=P x r^2 First, wall tension is proportional to vessel radius, according to Laplace’s law: T = P x r, where T is circumferential wall tension, P is transmural pressure, and r is mean vessel radius. Second, increased tension stress from blood pressure results in progressive vessel dilatation and weakening of aortic media, which lead to enlargement of aortic aneurysm. Third, when mechanical stress on wall exceeds strength of wall tissue, aortic aneurysm ruptures.

Question 27

Pascal’s principle and LaPlace’s Law

Answer 27

Pascal’s principle requires that the pressure is the same everywhere inside a balloon at equilibrium. But, there are great differences in wall tension on different parts of the balloon. The variation is described by LaPlace’sLaw. So places with greatest diameter, have highest wall stress at a given pressure

Question 28

Deep venous thrombosis velocity waveform: normal vs abnormal

Answer 28

• normal: normal phasic flow
• DVT: abnormal continuous flow

Question 29

Pressure in leg abnormally _______ with PAD. Blood velocity ______ with stenosis. The bigger the aneurysm, the _____ the risk of rupture. DVT causes loss of normal _______ and becomes ________.

Answer 29

• decreases
• increases
• higher
• normal phasic flow, becomes continuous flow