Peripheral Arterial Disease Review

What is the resistance equation, and what do the variables represent?

R = 8Lη ÷ πr⁴

• R = resistance

• L = length of vessel

• η = viscosity of blood

• r = radius

Which factor has the greatest effect on vascular resistance?

Radius, because it is raised to the 4th power

What is Poiseuille’s equation for volume flow?

Q = ΔPπr⁴ ÷ 8Lη

Also:

Q = ΔP ÷ R

How do pressure gradient, resistance, and radius affect blood flow?

• ↑ Pressure gradient → ↑ flow

• ↑ Resistance → ↓ flow

• Small changes in radius can cause large changes in flow

What principle does Bernoulli’s equation describe, and what 3 stenosis findings does it help explain?

Conservation of energy.

It explains:

1. Pressure drop across a stenosis

2. Increased velocity across a stenosis

3. Post-stenotic changes

Bernoulli’s equation - PE(1) + KE(1) + GE(1) = PE(2) + KE(2) + GE(2) + bruit

What happens to Doppler velocity at an arterial narrowing?

Velocity increases at the narrowing as blood passes through the reduced area

List the 6 clinical signs of chronic arterial insufficiency.

• Loss of hair growth

• Thickened toenails

• Thin, shiny skin

• Dependent rubor

• Pallor with elevation

• Delayed capillary refill

What do dependent rubor and elevation pallor indicate?

• Dependent rubor: Redness when the limb is lowered

• Elevation pallor: Pallor when the limb is raised

• Both indicate poor arterial inflow

How do arterial and venous ulcers differ in pain, location, and appearance?

Arterial:

• Painful

• Bony prominences/dorsum

• Dry

Venous:

• Painful, but limited

• Gaiter zone/medial malleolus

• Ooze and weepy

Where are arterial ulcers usually located, and what do they look like?

Usually on the toes or distal foot, with:

• Well-defined borders

• Pale or necrotic appearance Peripheral Artery Review 2026

Why do arterial ulcers develop, and what is necessary for treatment?

They result from prolonged ischemia, causing inadequate oxygen delivery, tissue death, and impaired healing.

Treatment requires restoring blood flow; wound care alone is insufficient.

How does acute arterial disease present compared with chronic arterial disease?

Acute:

• 6 P’s

   Pain

   Pallor: “pale”

   Pulselessness

   Paresthesia

   Paralysis

   Poikilothermia

• Emergency

• Sudden occurrence

Chronic:

• Thickened toenails

• Dry, scaly skin

• No muscle tone

• Dependent rubor

• Elevation pallor

• Claudication/rest pain

• Ulcers

What is claudication versus rest pain?

• Claudication: Cramping pain during exercise that is relieved by rest

• Rest pain: Pain at baseline metabolic demand, especially at night, indicating advanced arterial diseas

What is often the earliest symptom of acute arterial occlusion, and what test is commonly used?

• Earliest symptom: Severe pain

• Test: Doppler ultrasound to locate the blockage and assess flow

List the 3 treatment options for acute arterial occlusion.

• Anticoagulation

• Thrombolysis

• Surgery

What are the 3 components of a normal triphasic lower-extremity arterial waveform?

• Forward flow in systole

• Brief diastolic flow reversal

• Late diastolic forward flow

What does a tardus-parvus waveform look like, and what does it indicate?

• Dampened amplitude

• Prolonged systolic upstroke

Indicates delayed flow from an upstream stenosis.

What does a monophasic waveform indicate?

Severe/critical arterial disease with loss of the normal waveform complexity.

What happens to velocity-measurement accuracy as the Doppler angle approaches 90°, and what angle should be used?

• Accuracy decreases as the angle approaches 90°

• Correct angle alignment should be <60°

What is the short-form Doppler equation, and what do positive and negative shifts mean?

ΔDS = Received − Sent

• + = toward the transducer

• − = away from the transducer

What is the long-form Doppler equation for Doppler shift?

ΔDS = 2vf cosθ ÷ c

What is the equation for blood velocity using the Doppler equation, and what is the speed of sound in soft tissue?

V = ΔDS × c ÷ 2f cosθ

Speed of sound = 1540 m/s

List the 3 types/methods of arterial bypass grafts given.

• Gore-Tex

• In-situ venous graft — uses a valvotome

• Reversed venous graft

List the 5 bypass locations given.

• Aorto-bifemoral

• Fem-fem

• Fem-pop

• Axillary-femoral

• Fem-tibial

What velocity findings indicate abnormal bypass-graft function?

• >50% stenosis: Velocities double

• >70% stenosis: Velocities triple

• <45 cm/s: Impending failure

• Absent flow: Abnormal

List the 3 vascular graft types described on the review slide.

• In-situ saphenous vein

• Reversed saphenous vein

• Synthetic graft

Why are graft velocities monitored, and what is the clinical goal of a bypass graft?

• Velocity measurements assess graft patency

• Significant velocity drops may indicate stenosis or failure

• Goal: Restore blood flow and relieve symptoms such as claudication

What is a TIPSS, and where is the shunt created?

A shunt between the:

• RHV

• RPV

List the 3 clinical indications for TIPSS.

• PHTN

• Esophageal varices

• Bridge to transplant

List the 4 normal TIPSS parameters.

• Velocity 90–190 cm/s

• LPV — hepatofugal

• Minimal ascites

• Absent varices

List the 5 abnormal TIPSS parameters.

1. Velocity <90 or >190 cm/s

2. LPV — hepatopedal

3. Ascites

4. Varices

5. Absent flow in the stent

Also abnormal: MPV <30 cm/s.

List the 4 features of angiography.

• Contrast/X-ray dye

• Ionizing radiation

• Invasive

• Can show filling defects

How do CTA and MRA differ according to the slide?

CTA:

• Contrast/X-ray dye

• Ionizing radiation

• Can assess EVAR for endoleaks - GOLD STANDARD

MRA:

• Contrast

• Nonionizing radiation

What is transmural pressure versus intramural pressure?

• Transmural pressure: Difference between intravascular pressure and surrounding tissue pressure — inside vessel compared with outside

• Intramural pressure: Pressure within the vessel-wall tissue

What happens when transmural pressure increases, and what normal situation increases it?

When TMP increases:

1. Vein fully distends

2. Resistance to blood flow decreases

A normal example is standing, which increases transmural pressure.

List the 4 signs and symptoms of venous insufficiency.

• Varicose veins

• Edema

• Ulcers

• Skin discoloration

What happens when venous valves become incompetent?

They allow antegrade and retrograde flow, causing increased distal transmural pressure and:

1. Venous pooling

2. Edema

3. Venous insufficiency