Lower Extremity Arterial Testing and Evaluation

What is a basal state?

Steady state in metabolism of systemic blood pressure

What is an ABI?

Ankle to brachial index

What are segmental pressures?

Blood pressures obtained from cuffs placed around ankles, calves, and thighs

What is infrainguinal?

Below groin

What are the indirect physiologic tests?

1. Pressure assessment

2. Plethysmography

3. Doppler waveform analysis

4. Exercise stress test

What is a pressure assessment?

1. ABI

2. Segmental pressures

What is plethysmography?

1. Pulse volume recording (PVR)

2. Photoplethysmography (PPG)

What are the different bruit grades?

1. Grade 1+: Mild

2. Grade 2+: Moderate

3. Grade 3+: Severe

What is considered to be a “severe" bruit?

Abnormal blood flow that extends throughout diastole

What is the proper technique for Doppler waveform analysis of the lower arteries?

1. Patient in basal state or warm room

2. High frequency CW transducer

3. Transducer at 40-60 degree angle to skin

4. Obtain clean waveforms

What is analog analysis?

Use of zero crossing frequency meter to display waveforms on a graph or strip chart

What are the disadvantages of analog analysis?

1. Noise

2. Overestimates high frequencies

3. Underestimates low frequencies

4. Angle of insonation is operator dependent

Identify this image.

Analog zero-crossing detector

What is spectral analysis?

Use of FFT to display velocities or frequencies and amplitudes of backscattered signals

What is an advantage of spectral analysis?

Increased sensitivity to display multiple frequencies at once

Identify this image.

FFT color spectrum analyzer

Doppler analysis is…

Qualitative

What is happens to the acceleration time (AT) if there is an obstruction proximal to the probe?

Increased AT or tardus parvus waveform

What is happens to the acceleration time (AT) if there is an obstruction distal to the probe?

No change in AT

Identify this image?

Acceleration time (AT)

(T/F) Degree of obstruction cannot be determined on the basis of waveforms alone.

True; Collateralization of occlusions can restore flow distal to an occluded vessel

(T/F) Monophasic waveforms can only be obtained distal to an obstruction.

False; Monophasic waveforms can be obtained proximal AND distal to an obstruction

What is the segmental pressure principle?

Normal individuals in supine: Ankle systolic pressure ≥ Brachial systolic pressure

What is the proper technique for segmental pressure analysis of the lower arteries?

1. Patient in basal state or warm room

2. Patient in supine position with extremities at level of heart

3. Correct cuff size and placement

What is the correct blood pressure cuff size?

1. 20% greater than diameter of limb

2. 40% of limb circumference

Too tight blood pressure cuffs will…

Overestimate BP

Too loose blood pressure cuffs will…

Underestimate BP

Identify this image.

A. Bladder length

B. Cuff width

What is the recommended amount of inflation to use with the blood pressure cuffs in general?

DO NOT EXCEED 220 mmHg

What is the three cuff method?

Use of one large (17-19 x 40 cm) thigh cuff with normal thigh pressure EQUAL to brachial pressure

What are the normal and abnormal thigh pressure when using three cuff pressure method?

1. Normal: All pressures should be near equal to brachial pressure

2. Abnormal: Thigh pressure is 20-30 mmHg less than brachial pressure

What is the four cuff method?

Use of two smaller (12 × 40 cm) thigh cuffs to provide proximal and distal thigh pressures

What are the normal and abnormal pressure when using the four cuff method?

1. Normal high (proximal) thigh pressure: Thigh pressure is 20 mmHg greater than brachial pressure

2. Abnormal high (proximal) thigh pressure: Thigh pressure less than brachial pressure

3. Abnormal: High thigh and low thigh having a 30 mmHg pressure difference is suggestive of SFA disease

Why is there a pressure artifact when using the four cuff method?

Use of narrow high thigh cuff that elevates pressure 20-30 mmHg

What is the key difference between the three cuff and the four cuff method?

Four cuff method can differentiate between aortic-iliac (AI) and superficial femoral (SFA) disease

In general, what is considered to be a significant pressure gradient or drop in pressure for an abnormal ABI?

30 mmHg

Identify this image.

Abnormal left pressure due to decrease in at least 20 mmHg suggesting subclavian artery disease

What is the formula for finding the ABI?

Bilateral ankle pressures divided by highest brachial pressure

What is the highest ankle pressure marker used for?

Reported for ABI

What is the lowest ankle pressure marker used for?

Marker for PAD

Identify this image.

Normal ABI

What are the normal resting ABI values?

1. > 1.35 = Probable calcified arteries

2. 1.0-1.34 = NORMAL

3. 0.9-1.0 = Minimal arterial disease

4. < 0.9 = Abnormal

5. < 0.8 = Probable claudication (leg pain w/ exertion)

6. < 0.5 = Multi-level disease and long segment occlusion

7. < 0.3 = Rest pain, severe disease, ischemia

8. < 0.2 = Tissue loss or gangrene

What occurs when systemic blood pressure is less than 100 mmHg or greater than 200 mmHg?

Ankle pressure is typically 25% lower than brachial pressure

In healthy (normal) people, what is the difference between systolic ankle pressure and systolic arm (brachial) pressure?

Systolic pressure in ankle is normally HIGHER than in arm due to amplified BP as blood travels away from heart

How do you distinguish between the dorsalis pedis artery (DPA) and the posterior tibial artery (PTA)?

1. DPA= Easily compressed and harder to locate

2. PTA= Harder to compress and easier to locate

Identify this image.

DPA for ABI

Identify this image.

PTA for ABI

(T/F) The probe should be held at a 90 degree angle when locating the PTA.

False; 45-60 degrees is best

What are the steps for taking segmental pressures?

1. Inflate cuffs to at least 20 mmHg above systolic arm pressure

   • Narrow high-thigh cuff inflated to 40 mmHg above arm pressure

2. Pause for a moment

3. Slowly lower pressure

4. Record returning systolic pressures

Which of the lower arterial test modalities provides diagnostic quantitative information?

Segmental pressures

What is photoplethysmography (PPG) when discussing segmental pressures?

Measurement of change in SYSTOLIC AND DIASTOLIC blood volume in different parts of body using infrared light to detect RBCs

What are the advantages of PPG segmental pressures?

1. Less operator dependent

2. Bilateral capability

What are the disadvantages of PPG segmental pressures?

1. No audible signal

2. Not able to use with severe disease

3. Motion and ambient light artifact can cause false readings

How do we take toe or digital pressures?

Cuff on toe or other digit that takes small pressures (1.9 or 2.5) alongside use of PPG transducer to display SYSTOLIC blood flow

When are toe pressures used?

1. Evaluating small vessel disease

2. Evaluating calcified, incompressible large vessels in diabetic patients

What is the normal toe / brachial index (TBI)?

Normal > 0.75 (60-80%)

What is the abnormal toe / brachial index (TBI)?

Abnormal < 0.66

What are the limitations of segmental pressure exams?

1. Diabetics medial calcinosis or calcification of arteries

2. Chronic steroid therapy

3. Renal dialysis patients

4. Segmental pressures unobtainable or excessively high (ABI > 1.35) PTA

In those with calcified arteries (medial sclerosis), how must you determine limb perfusion (BP)?

Combination of PVR, Doppler waveform analysis, or toes pressures due to unusable segmental pressures

What are some calcification clues?

1. Incompressible artery

2. Unobtainable pressures

3. Excessively high ABI (> 1.35)

4. High distal limb pressure

What is the correct way to obtain an ABI?

1. Right ankle / Highest arm or brachial

2. Left ankle / Highest arm or brachial

3. Lowest of two = ABI

(T/F) Toe pressures are more reliable than ankle pressures.

True; Toe vessels are less likely to be affected by calcification

When should exercise or stress testing be utilized when measuring ABIs?

1. Patient complains of intermittent claudication

2. ABI of 0.85-0.5

When should exercise or stress testing NOT be utilized when measuring ABIs?

1. Patient on Beta Blockers or Isorobides because they will not allow increase in heart rate

2. Patients with pulmonary or cardiac disease

3. ABI < 0.3

What can be interpreted from an exercise or stress ABI?

1. Ankle pressures that drop to low levels and recover to resting levels within 2-6 minutes post exercise suggest single level obstruction

2. If pressures remain reduced for up to 12 minutes, multilevel obstructions are present

What is the normal ankle pressure response to exercise or stress ABI testing?

No change to slight increase in pressure

What is the exercise or stress pressure value that indicates vascular claudication?

Ankle pressure of 60 mmHg or less

What is a substitution for a treadmill for an exercise or stress ABI?

Toe raises for one minute or until claudication symptoms return

What is assessed during exercise or stress ABI?

1. Exercise tolerance

2. Recovery time

3. Pressure drop

4. Diagnose leg pain

What are the disadvantages of an exercise or stress ABI?

1. Detects hemodynamically significant disease or > 60% stenosis

2. Cannot distinguish stenosis from occlusion

3. Locates general area of disease

What is the alternate test to an exercise or stress test?

Reactive hyperemia (PORH)

What is reactive hyperemia testing (PORH)?

Alternative method for stressing peripheral circulation system by inflating cuffs 20-30 mmHg above brachial pressure for 3-5 minutes

What is the result of a reactive hyperemia test (PORH)?

1. Ischemia and vasodilation distal to cuff

2. Single vessel disease seen as < 50% pressure drop in ankle

3. Multi-level disease seen as > 50% pressure drop in ankle

What is pulse volume plethysmography (EVR or PVR) when discussing segmental pressures?

Measurement of change in SYSTOLIC blood volume in different parts of body using pneumo-plethysmography, Doppler waveforms, and segmental pressures

What is the recommended amount of inflation to use with the blood pressure cuffs during PVR studies?

65 mmHg

What are the advantages of pulse volume plethysmography (EVR or PVR)?

1. Differentiates arterial claudication from nonvascular sources

2. Detects true arterial disease

3. Locates general area of obstruction

What are the disadvantages of pulse volume plethysmography (EVR or PVR)?

1. Cannot be specific to a single vessel

2. Cannot differentiate between major arteries and collateral obstruction

3. Not best with obese patients

4. Tremor or motion artifact

(T/F) PVR can be used alone to diagnose arterial disease.

False; Collateralization of an obstruction can produce a normal PVR when segmental pressure of same region indicates severe disease

Which of the following conditions would cause an abnormal pulse volume recording (PVR) at the high-thigh location?

Significant aortoiliac disease

What is strain gage plethysmaography (SGP)?

Measurement of change in blood volume in different parts of body using a mercury-filled plastic tube

What is duplex scanning?

Combination of b-mode and PW Doppler to create images and measure blood flow

What are the advantages of duplex scanning?

1. Localizes arterial stenosis and occlusion

2. Evaluates degree of stenosis

3. Determines presence of aneurysms

4. Evaluates arterial bypass grafts and hemodialysis access grafts

5. Detects AV fistulas

What are the disadvantages of duplex scanning?

1. Presence of dressings, open wounds, skin staples, sutures limits visualization of vessels

2. IV sites and other puncture sites in groin inhibit visualization

3. Obese patients difficult to image

(T/F) Normal PW Doppler signal should show triphasic flow.

True; Biphasic and monophasic patterns are abnormal

What is the blood supply to the penis?

1. Hypogastric artery to base of penis

2. Internal pudendal artery to base of penis

What is the blood supply within the penis?

1. Cavernosal arteries that supply main erectile tissue (corpora cavernosa)

2. Bulbourethral artery

3. Dorsal artery

With erection, flow resistance in the corpora cavernosa…

Increases

Normal erectile function requires… and…

Sufficient arterial inflow; Decreased venous outflow

What is a major cause of penile impotence?

Insufficient veno-occlusive mechanism from a venous leak

What are the risk factors of penile impotence?

1. Diabetes mellitus

2. HTN

3. PAD

4. Tobacco abuse

5. Arterial bypass surgeries

6. Prostatectomy

What is the indication for a penile arterial exam?

Determine if impotency or failure to maintain an erection is due to peripheral vascular insufficiency

What are possible reasons for vascular insufficiency to the penis?

1. Pelvic steal

2. Arterial vasospasm

3. Arterial occlusive disease

What size blood pressure cuff is used for a penile arterial exam?

1. 2.5 × 12.5 cm

2. 2.5 × 9 cm

What is the equation for a penile brachial index (PBI)?

Penile systolic pressure / Brachial systolic pressure

What are the values for PBI?

1. Normal= ≥ 0.75 (or 0.7-1.0)

2. Marginal or Borderline Normal = 0.65-0.74 (or 0.6-0.7)

3. Abnormal = < 0.65 (or less than 0.6)

How do you perform penile imaging?

1. Scan flaccid penis in trans and long views to identify plaque and locate corpora cavernosa and cavernosal arteries

2. Record Doppler waveforms (PSV & EDV)

3. Prostaglandin E-1 or Pavaparine injection

4. Rubber band applied to base for two minutes

5. Doppler PSV and EDV measurements are taken from the proximal cavernosal arteries at 5, 10, 15 and 20 minutes post injection

6. Normal erectile response should occur within 10 minutes and erection should be maintained for 30 minutes

What are the normal PSV and EDV values during erectile state?

1. PSV > 35 cm/sec

2. EDV > 5 cm/sec

What are the abnormal PSV and EDV values during erectile state?

1. PSV < 25 cm/sec

2. PSV > 35 cm/sec, but EDV is > 6 cm/sec (venous leak)

3. Vessel diameter increases less than 75%