tibial vessels remain patent. High-grade stenosis may also progress to occlusion without a change in

ABI.

Table 87-3 Correlation between Ankle Brachial Index and Clinical Severity of

Lower Extremity Arterial Ischemia

Segmental Limb Pressures

Multiple pneumatic cuffs may be used along the lower extremity to determine the arterial blood

pressure at specified levels. These “segmental leg pressures” are compared with the higher brachial

artery systolic pressure, with other locations in the ipsilateral leg and with the corresponding levels in

the contralateral extremity. Three or four cuffs may be used. In the four-cuff technique cuffs are placed:

(1) as far proximal on the thigh as possible; (2) immediately above the knee; (3) just below the knee;

and (4) just proximal to the ankle. Each cuff width should be 20% greater than the diameter of the limb

at the point of application to avoid falsely elevated pressure readings induced by too narrow a cuff.30

For the thigh, this generally necessitates a single, wide, thigh cuff. Use of two cuffs above the knee,

however, can permit assessment of inflow at or proximal to the common femoral artery with the

proximal cuff, and permit evaluation for the presence of superficial femoral artery disease by the distal

thigh cuff. With two thigh cuffs the most proximal thigh cuff is often too narrow. An artificially

elevated pressure in the proximal thigh is then expected. Therefore the high-thigh index, comparing the

proximal thigh pressure to the brachial pressure, is normally about 1.4 with the four-cuff technique and

1.0 to 1.1 with the three-cuff technique (Fig. 87-10).

A hand-held Doppler is used to detect the most prominent Doppler signal at the ankle. Examination

proceeds proximal to distal. First the high-thigh cuff is inflated until the ankle Doppler signal is no

longer audible. The cuff is then deflated and the pressure where there is return of the Doppler signal at

the ankle is the high-thigh pressure. The above-knee, below-knee, and ankle pressures are similarly

determined. If there is no audible ankle Doppler signal, the popliteal artery is insonated with the

Doppler to determine high-thigh and above-knee pressures. Comparison of the pressures measured at

each location permits an estimation of the location of occlusive lesions (Fig. 87-11).

Figure 87-10. Segmental pressures multiple pneumatic cuffs may be used along the lower extremity to determine the arterial

blood pressure at each level. Comparison of the pressures measured at each location permits an estimation of the location of

occlusive lesions. Use of two cuffs above the knee can permit assessment of inflow at or proximal to the common femoral artery

with the proximal cuff, and permit evaluation for the presence of superficial femoral artery disease by the distal thigh cuff. In

many patients, however, the high-thigh cuff is relatively narrow compared to the diameter of the thigh resulting in an artificial

elevation of the high-thigh pressure so that with use of four cuffs the high-thigh pressure will be 30 to 40 mm Hg higher than the

highest brachial pressure.

There are multiple limitations in the interpretation of segmental limb pressures. The high-thigh

pressure is subject to particular interpretation difficulties. A diminished high-thigh pressure can reflect

an occlusive lesion anywhere at or proximal to the common femoral artery bifurcation. Low high-thigh

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pressures therefore may reflect a pressure-reducing stenosis in the ipsilateral common or external iliac

artery, a common femoral artery lesion or tandem pressure-reducing lesions in the profunda femoris and

the proximal superficial femoral artery or any combination of such lesions. The accuracy of segmental

pressures may be affected by mural calcification resulting in artificially elevated pressures. Diminished

proximal pressures may also mask gradients that exist further down the leg. Segmental pressures also do

not allow differentiation between short- and long-segment occlusions, or between occluded and patent,

but highly stenotic arteries.

Figure 87-11. Segmental pressure examination with use of thigh, calf, and ankle cuffs. A drop in pressure of 30 mm Hg between

levels indicates a hemodynamically significant stenosis between the two adjacent cuffs. This study therefore indicates a flowreducing lesion somewhere at or proximal to the common femoral artery bifurcation on the right side and likely superficial

femoral artery/popliteal artery occlusive disease on the left.

Exercise Testing

Doppler-determined pressures can be combined with treadmill exercise testing in patients without a

contraindication to exercise. After determination of resting supine ankle pressures and ABIs, the patient

walks on a treadmill with a predetermined incline at a predetermined rate. The test continues for 5

minutes or until the patient is forced to stop. The type, time-to-onset, and location of symptoms are

recorded. At completion of the test, the patient is immediately placed supine and absolute ankle

pressures and ABIs determined.

In most patients exercise testing serves only to confirm a diagnosis of claudication. It is not required

in a patient with classic symptoms of claudication, absent peripheral pulses and a diminished ABI. In

some cases exercise testing can document a physiologic response to revascularization or provide an

objective assessment of the potential postoperative physiologic benefit.

Exercise testing is particularly useful in the infrequent patient with symptoms of claudication and who

has palpable pedal pulses and/or a normal ABI. Patients with exercise-induced leg pain occurring on the

basis of arterial insufficiency will show a decrease in the postexercise ankle pressures and ABI. Exercise

testing can also be used to document an ischemic response to exercise in a patient with PAD and other

conditions that may limit their ability to walk. Patients with COPD, arthritis, venous disease, and PAD

are often more limited in their walking ability by these coexisting conditions than by their PAD. If the

patients cannot complete a treadmill examination, and no ischemic pressure response to exercise occurs,

it is highly unlikely their walking ability would be improved by a revascularization procedure.

The precise endpoints and techniques of exercise testing are controversial. Some laboratories exercise

patients at low speeds with no inclination of the treadmill whereas others utilize various inclines and

graded increases in treadmill speed. Both initial and absolute claudication distances can be determined.

Initial claudication distance is the point where the patient initially experiences claudication-type pain.

The absolute claudication distance is where the patient can no longer continue to walk on the treadmill.

Criteria for a positive exercise test include a decrease in the ankle pressure of 20 mm Hg or 20%, a

decrease in the ABI of 0.2 in the symptomatic extremity, or failure of the ankle pressure to return to

baseline within 3 minutes of completing the treadmill portion of the examination. Because systemic

pressure and therefore arm pressures, depending on work load, will increase with exercise, use of the

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ABI alone to indicate a positive exercise test is incorrect. The ABI decrease should be accompanied by an

absolute pressure drop at the ankle.

7 Failure of the ankle pressure to drop with exercise along with failure of the ABI to decrease 20%

with exercise, combined with a normal resting ABI, substantially rules out arterial insufficiency as the

etiology of the patient’s exercise-induced complaints of leg pain. An exception is the rare patient with

buttock claudication secondary to isolated internal iliac disease.

Neurogenic claudication may be confused with arterial ischemia. Patients present with symptoms of

exercise-induced leg or calf pain. Careful questioning, however, reveals atypical characteristics for

vascular-induced exercise-associated pain. Such characteristics include occurrence of pain with standing,

pain relief when leaning forward, worsening with coughing, and prolonged time for pain to resolve

following exercise. These patients often have normal ankle pressures at rest that do not decrease with

exercise despite onset of symptoms. Failure of the ankle pressures to decrease with exercise may also be

a clue to the presence of other uncommon conditions, such as venous claudication and chronic exerciseinduced compartment syndromes.

Doppler Analog Waveform Analysis

Similar to plethysmographic waveforms, continuous-wave Doppler waveforms may also be analyzed

qualitatively. Normal lower extremity Doppler waveforms are described as triphasic with a sharp

systolic upstroke, an end-systolic reverse flow component followed by low flow forward through

diastole. The shape of the waveform changes with increasing severity of proximal obstruction. Initially,

the reverse-flow component is lost. As proximal stenosis increases, the rate of rise of the systolic

upstroke is decreased, the amplitude of the waveform is diminished, and diastolic flow increases

relative to systolic flow.

Continuous-wave Doppler waveforms are generally used in conjunction with measurement of

segmental Doppler pressures similar to the use of PVRs. Doppler waveform analysis can also be used to

assess iliac artery inflow to the common femoral artery. An attenuated common femoral artery

waveform indicates proximal disease.

Peripheral Artery Duplex Scanning

Arterial duplex scanning provides detailed anatomic and hemodynamic information from the infrarenal

aorta to the distal tibial vessels that cannot be determined by indirect testing. Arterial duplex scanning

has been prospectively compared with angiography to establish standard criteria for normal and

diseased arteries.31 Sensitivity of duplex examination for detecting the presence of a hemodynamically

important lesion (>50%) ranges from 89% at the iliac artery to 68% at the popliteal artery. Overall

sensitivities for predicting interruption of patency are 90% for the anterior and posterior tibial arteries

and 82% for the peroneal artery. The technique is versatile and does not appear to be significantly

influenced by the presence of previous operations or multilevel disease (Fig. 87-12A,B).

Velocity Patterns and Classification of Percent Stenosis

In the absence of arterial stenosis or occlusion triphasic waveforms are maintained throughout the

length of the lower extremity but PSV decreases from the iliac to the tibial vessels. There are no

significant differences in velocity measurements among the three tibial arteries in normal subjects.

Important changes in the velocity waveforms that signify disease include the absence of an endsystolic reverse flow component and elevation of the PSV. A 50% reduction in arterial luminal diameter

(equivalent to a cross-sectional surface area reduction of 75%) is associated with a pressure drop across

the lesion. The University of Washington criteria for classification of peripheral arterial stenosis are

shown in Table 87-4.32

Table 87-4 University of Washington Duplex Criteria for Determination of

Stenosis in Lower Extremity Arteries

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Figure 87-12. A: Duplex images/waveforms and corresponding angiogram of an abrupt popliteal artery occlusion. B: Duplex

waveforms and angiographic images in a patient with severe in-stent stenosis of superficial femoral artery stents.

A PSV ratio, comparing the velocity within the stenosis to the velocity just proximal to the stenosis, is

also useful for grading degree of stenosis. PSV ratios are independent of changes in blood pressure,

cardiac output, and vascular compliance. Grading stenosis using the PSV ratio has been found to be

highly reproducible.33,34 Fifty percent stenosis in lower extremity arteries correlates with a PSV ratio

from 1.4 to 3.0.31,35–38 A velocity ratio of 2.0 is a reasonable compromise and is used by many vascular

laboratories as indicative of a 50% peripheral arterial stenosis.

Lower extremity duplex scanning can serve as an alternative to contrast arteriography in the

preoperative assessment of candidates for arterial intervention. In selected centers, successful lower

extremity revascularization either by open arterial bypass grafting or with catheter-based techniques has

been reported using only arterial duplex in a high percentage of cases.39–41 The limiting factor with

preoperative arterial duplex is the ability to accurately identify the best site for the distal anastomosis

of a bypass graft, especially when the distal anastomotic site is below the knee.42

The role of duplex ultrasound scanning in the surveillance of lower extremity vein grafts has been

well documented (Fig. 87-13A,B). Detection and repair of a graft-threatening stenosis detected by

duplex scanning appears to improve secondary graft patency.43–46 Twenty to thirty percent of vein

grafts will develop a severe enough stenosis that revision is recommended.47 Approximately 80% of

these graft stenotic lesions develop in the first postoperative year. However, graft threatening lesions

can develop at any time. Surveillance is therefore generally recommended for the life of the graft. A

widely utilized protocol for vein graft duplex surveillance is every 3 months for the first year and every

6 months to yearly thereafter. The examination involves point-to-point insonation of the proximal

inflow artery, proximal anastomosis, midgraft, distal anastomosis, and the distal outflow artery. A PSV

ratio of 4, or a PSV above 300 cm/s, indicates a critical graft stenosis, and repair of the lesion by open

or catheter-based techniques should be considered.48 If the PSV ratio is between 2 and 4, the patient

should be evaluated again in 3 months with a duplex examination.

Aneurysms and pseudoaneurysms of lower extremity arteries are also readily identified and

characterized with duplex scanning with particular attention to the diameter of the aneurysm and the

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presence or absence of intraluminal thrombosis (Fig. 87-14A,B).

Figure 87-13. A and B: Duplex ultrasound images and velocity waveforms of normal (A) and stenotic (B) proximal anastomoses of

femoral tibial bypass grafts. The abnormal study has a severe elevation in flow velocity of 558 cm/s indicating a high-grade

stenosis.

Figure 87-14. A: Native popliteal artery aneurysm with intraluminal thrombus. B: Large pseudo aneurysm of the right common

femoral artery resulting from arterial infection from intra-arterial injection of street drugs.

Upper Extremity Arterial Evaluation

Upper extremity arterial disease is a small but important component of vascular surgical practice. Both

ultrasound and plethysmographic techniques are important in the evaluation of upper extremity arterial

disease.

SEGMENTAL ARM PRESSURES

Upper extremity segmental pressures are obtained by measuring blood pressure with pneumatic cuffs

above the elbow, below the elbow, and above the wrist while insonating the radial or ulnar artery at

the wrist using a continuous wave Doppler. Doppler-derived or plethysmographic waveforms can also

be recorded at the different levels. Abnormal waveforms or pressures will help diagnose arterial disease

proximal to the wrist.

A 12-cm blood pressure cuff is usually sufficient for measuring the brachial artery pressure, whereas a

10-cm blood pressure cuff is used at the wrist to measure the systolic pressure from the radial and ulnar

arteries. A systolic pressure measurement is taken from the upper arm (brachial artery) and at the wrist

(radial and ulnar arteries). Normally, there is not a recordable gradient between any of these sites and a

normal wrist/brachial blood pressure ratio is 1.0. If there is a blood pressure difference between the

two arms of more than 15 mm Hg, it is likely that there is a stenosis or occlusion somewhere on the

side of the lower pressure. Abnormal waveforms and decreased pressures at the above-elbow cuff site

indicate axillary, subclavian, or brachiocephalic arterial occlusive disease. Similarly, abnormalities at

the below-elbow and above-wrist sites indicate brachial and proximal ulnar/radial arterial occlusive

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disease, respectively. If there is a blood pressure difference between levels, or between the radial and

ulnar arteries, of more than 15 mm Hg it is likely caused by a stenosis or occlusion (Fig. 87-15).

DIGITAL PRESSURES AND PLETHYSMOGRAPHY

Digital pressure measurements and digital plethysmography are extremely useful in the diagnosis of

upper extremity arterial disease and can be as accurate as arteriography in assessing patients with hand

ischemia.49 Photo plethysmography (PPG) or strain-gauge plethysmography can be used to measure

digital blood pressure and to obtain pulse waveforms. PPG is preferred because the equipment is easier

to use and more durable. An additional advantage of PPG is that it is possible to record the volume

pulses from the tips of the digits. This may also be useful in documenting obstruction within the digit

arteries themselves.

The photo cell is attached to the fingertip pulp with double-sided tape or small strain gauges are

placed around the fingertip. One-inch (2.5 cm) blood pressure cuffs are placed around the proximal

phalanx. Waveforms are recorded using pulse tracings obtained at high speed to evaluate the shape of

the waveform. Waveforms are normal if the upstroke time is less than 0.2 seconds (Fig. 87-16A). They

may or may not have a dichotic notch. An abnormal obstructive waveform will have a rounded peak, as

opposed to the normal notched peak. Upstroke time is prolonged. The amplitude of the waveform is not

important. Finger PPG waveforms are not quantitative. The amplitude of the waveform is primarily

dependent on the gain setting, not blood flow.

Patients with vasospasm will often have an abnormally shaped waveform termed a “peaked pulse,”

which is thought to represent abnormal elasticity and rebound of the palmar and digital vessels (Fig. 87-

16B).

Finger blood pressures are measured by inflating the cuffs placed at the base of the fingers. At

reduced chart recorder speed the pulsations are recorded while the blood pressure cuffs are inflated.

When digit pulsations are obliterated, the cuff is slowly deflated until the pulsation returns. The

pressure reading at this point is recorded and represents the digital artery pressure.

It is extremely important to measure and record finger temperature before performing digital

plethysmography and obtaining finger blood pressures. If the finger temperature is less than 28 to 30°C

false-positive results may be obtained secondary to cold-induced vasospasm. It is recommend that hand

and/or whole-body warming be performed in patients with low finger temperatures.

Digital blood pressure is normally within 20 to 30 mm Hg of brachial pressure. A ratio of finger

systolic pressure to brachial systolic pressure of greater than 0.80 is normal but does not necessarily

rule out digital artery occlusive disease. It is important to remember that there are occasional patients

with very distal digital artery occlusive disease with normal finger pressures since the digital cuff is

around the proximal phalanx. Also, occlusive disease in a single digital artery can be missed if the other

digital artery in that finger is normally patent.

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Figure 87-15. Upper extremity segmental pressures and Doppler waveforms. The findings are normal on the right and suggest

radial and ulnar artery or distal brachial artery occlusive disease on the left.

COLD CHALLENGE TESTING

The simplest cold intolerance test is to measure the digital temperature recovery time after immersion

of the hand in ice water for a short time period. Preimmersion digital temperatures must be above 30°C.

Hand and body warming may be required prior to immersion.

Using a thermistor probe to measure finger temperatures, the patient’s hand is immersed in a

container of ice water for 30 to 60 seconds. After the hand is dried, the fingertip pulp temperatures are

measured every 5 minutes for 45 minutes, or until the temperature returns to preimmersion levels.

Normal individuals will have a recovery time to preimmersion levels of less than 10 minutes. This test is

very sensitive for detecting cold-induced vasospasm but is nonspecific, with approximately one-half of

patients with a positive test having no clinical symptoms of cold sensitivity.50 Cold immersion testing is

also uncomfortable and poorly tolerated by patients with significant Raynaud syndrome symptoms.

Pressures often fall to unrecordable levels in such patients.

A better, but infrequently utilized, test for cold sensitivity is the digital hypothermic challenge test as

described by Nielsen and Lassen (Fig. 87-17).51 This test involves placing a finger cuff around the

proximal phalanx on the test finger and perfusing the cuff with progressively cooler fluid. The pressure

in the test finger is then compared with that in a reference finger that is not cooled. The Nielsen test is

interpreted as positive for abnormal cold-induced vasospasm if the test finger pressure is reduced by

more than 17% compared with the reference finger.

Other tests for cold-induced vasospasm include thermal entrainment, digital laser Doppler response to

cold, thermography, venous occlusion plethysmography, and digital artery caliber measurement. None

are widely accepted or employed.52–54

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