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14 2
LYMPHANGITIS
Patients with lymphangitis may report an erythematous patch or linear streak that affects the limb and tends to propagate proximally
over time. The erythematous area may be painful and tender. These
patients usually present with systemic signs of infection, including
CH
fever and shaking chills. History might determine whether lesions
11
induced by trauma or infection may have served as a portal of entry.
Vascular Examination
As in any comprehensive physical examination, vital signs (blood
pressure, heart rate, respiratory rate) should be assessed and
recorded. Blood pressure should be measured in both arms and
preferably in supine, seated, and upright positions. Overall appearance of the patient should be noted.
The vascular examination includes inspection, palpation, and
auscultation of vascular structures in many areas of the body. A
systematic approach ensures a complete evaluation, so the examination described in this chapter will cover principal anatomical
regions that are particularly relevant to the peripheral vasculature.
The heart, lungs, and neurological and musculoskeletal systems
should be examined, but details of these examinations are beyond
the scope of this chapter.
Limbs
The limbs should be inspected carefully, assessing their appearance, symmetry, color, and evidence of edema or muscle wasting.
PULSE EXAMINATION
The pulse examination of the arms and legs is a critical part of
the vascular examination. Asymmetry, decreased intensity, or
absence of pulses provide clinical evidence of PAD and indicate
the location of stenotic lesions. Some examiners describe pulses as
absent, diminished, or normal, or use a numerical scale (e.g., from
0 [absent] to 2+ [normal]). Bounding pulses may be evidence
of aortic valve insufficiency, and dilated expansive pulses a sign of
ectasia or aneurysm.
Pulses of the arms—brachial, radial, and ulnar pulses—should
be palpated using two or three fingertips. The brachial pulse is
superficial and in the medial third of the antecubital fossa. The
radial pulse, also superficial, can be found over the stylus of the
radius near the base of the thumb (
pated on the volar aspect of the wrist, over the head of the ulnar
bone. Wrist support by the examiner improves pulse detection by
decreasing overlying muscle tension.
Pulse examination of the leg (femoral, popliteal, posterior tibial,
and dorsalis pedis pulses) should be undertaken with the patient
supine. The femoral pulse is located deep, below the inguinal ligament, about midway between the symphysis pubis and iliac spine.
Obesity may obscure local landmarks. Lateral rotation of the leg,
pannus retraction, and two hands may be required for adequate
palpation. On occasion, the increase in flow velocity caused by a
stenosis may create a thrill in the common or superficial femoral
artery that is appreciated by palpation of the femoral pulse, or a
bruit that can be heard with auscultation.
Palpation of the popliteal pulse can be difficult. The leg should
be straight yet relaxed to decrease overlying muscle stiffness. The
popliteal pulse should be palpated with three fingers from each
hand while the thumbs are applying moderate opposing force to
the top of the knee (
found at the junction of the medial and lateral thirds of the fossa. In
contrast to superficial pulses like the radial or dorsalis pedis pulse,
the popliteal pulse is diffuse and deep. Widened popliteal pulses
may be indicative of popliteal artery aneurysm.
The posterior tibial pulse can be found slightly below and
behind the medial malleolus. Counterpressure with the thumb
and passive dorsiflexion of the foot may increase the likelihood of
Fig. 11-2). The popliteal pulse typically can be
Fig. 11-1). The ulnar pulse is pal-
FIGURE 11-1 Palpating radial pulse. Examiner, using three or four fingers,
lightly palpates the superficial radial pulse over stylus of radius near base of
thumb.
FIGURE 11-2 Palpating popliteal pulse. Popliteal pulse requires moderate
pressure for its appreciation. Examiner uses both thumbs for moderate opposing
force while placing digits two, three, and four in lateral third of popliteal fossa.
Patient's leg should be relaxed while examiner induces mild flexion. A widened
popliteal artery pulse may indicate presence of aneurysm.
palpation (
absence is diagnostic for PAD. In contrast, the dorsalis pedis pulse,
which can be appreciated just lateral to the extensor tendon on
the dorsum of the foot, normally may be absent in 2% to 12% of
persons.
Fig. 11-3). The posterior tibial pulse should be present. Its
FIGURE 11-3 Palpating posterior tibial pulse. Posterior tibial pulse resides
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slightly below and behind medial malleolus. It should be approached from the
lateral aspect, with digits applied to lower curvature of malleolus. Passive foot
dorsiflexion may enhance appreciation of pulse.
THE ALLEN TEST
The radial and ulnar arteries supply blood flow to the hand.
Within the hand, these arteries form the superficial and deep
palmar arches, enabling blood supply to the digits from either
vessel; 5% to 10% of the population has a congenitally incomplete arch. Disease states associated with interruption of the
palmar arch include connective tissue diseases like the CREST
variant (calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) of scleroderma, vasculitides like
TAO, and thromboemboli. The Allen test can differentiate between
a complete and incomplete palmar arch. The examiner occludes
both the radial and ulnar pulses (
Fig. 11-4), and the patient then
opens and closes the fist several times, creating palmar pallor. Upon release of one pulse, normal skin color should return
within seconds. The other artery is then tested and observed similarly. Persistent pallor is indicative of an incomplete palmar arch
or occluded artery distal to the remaining pulse occluded by the
examiner.
Nearly three quarters of all patients with TAO, will have a positive Allen test, and 50% will report Raynaud phenomenon. Digital
ischemia in these patients is more likely to progress and cause
persistent cyanosis and lead to digital ulcers. Patients with TAO
also may develop migratory superficial thrombophlebitis, which
appears as painful, tender, red nodules.
THORACIC OUTLET MANEUVERS
Thoracic outlet syndrome results from compression of the neurovascular bundle as it leaves the thoracic cavity. Each component of the bundle may be affected, including the brachial plexus,
subclavian/axillary artery, and subclavian/axillary vein.
Thoracic outlet maneuvers seek to elicit positional interruption of arterial flow. During the examination, the physician holds the radial pulse in one hand and maneuvers the
arm with the other. The subclavian artery is auscultated in the
supraclavicular fossa. An abnormal thoracic outlet maneuver is characterized by development of a subclavian bruit
followed by loss of the radial pulse. Several thoracic outlet
maneuvers have been described, and each may be relevant
to compression at different sites in the thoracic outlet. Each
side is examined in sequence. The Adson maneuver assesses
the segment of the subclavian artery in the scalene triangle.
The patient rotates his/her head toward the symptomatic
side, extends the neck (i.e., looking up and over the shoulder), and simultaneously performs an exaggerated inspiration. The costoclavicular maneuver assesses the segment of
the subclavian artery coursing between the clavicle and first
rib. The patient thrusts the shoulders back and inferiorly. The
hyperabduction maneuver evaluates the subclavian artery as it
courses near the insertion of the pectoralis major muscle. The
patient is seated and the head is looking forward. The arm is
abducted 180 degrees to a position along the side of the head.
Abduction of the arm to 90 degrees may be combined with
external rotation in evaluating symptoms suggestive of thoracic outlet syndrome (
Fig. 11-5). This maneuver is often used
to assess subclavian venous or arterial compression during
ultrasonography or angiography.
For patients in whom clinical suspicion for thoracic outlet syndrome is present, sensitivity and specificity for these provocative tests are 72% and 53%, respectively.
16
Routine application of
these maneuvers is not warranted, however, since up to 50% of
the population may have a positive finding. Indeed, in one study
of 64 randomly selected subjects, application of these maneuvers
in a nonspecific manner overdiagnosed the syndrome more than
threefold.
ticularly difficult group for these maneuvers and generate a falsepositive rate of nearly 50%.
17
Patients with carpal tunnel syndrome present a par-
18
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CH
11
THE HISTORY AND PHYSICAL EXAMINATION
A
FIGURE 11-4 Allen test. The Allen test determines presence or absence of a complete palmar arch. Both radial and ulnar pulses are occluded while patient
opens and closes hand to create palmar pallor. Once pallor is evident, examiner releases one pulse. In this example, patient presented with persistent fifth digit and
hypothenar cyanosis. A, Release of radial artery pulse results in expected hyperemia and palmar erythema. B, In contrast, release of ulnar artery pulse does not result
in palmar erythema, indicating proximal occlusion in ulnar segment of palmar arch. This test is considered a positive Allen test.
B
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11
FIGURE 11-5 Elevated Arm Stress Test (EAST) may be used to evaluate
subclavian artery as it courses near insertion of pectoralis major muscle.
Patient initially sits looking forward while arms are abducted 90 degrees, elbows
are abducted 90 degrees, and patient repeatedly makes a clenched fist. During
maneuver, radial pulse should be palpated while subclavian artery is auscultated.
Loss of pulse or development of subclavian artery bruit is a positive study.
LIMB ISCHEMIA
Skin color and temperature can provide information about severity of limb arterial perfusion. The feet, hands, fingers and toes
should be examined for temperature and skin color, and the nails
for evidence of fragility and pitting. Limb temperature can best be
appreciated using the back of the examiner's hand. Temperature
changes of adjacent segments on the ipsilateral limb and comparisons with the contralateral limb can be made. Presence of foot
pallor while the leg is horizontal is indicative of poor perfusion
and may be a sign of ischemia. Foot pallor may be precipitated in
patients with PAD (who do not have CLI) by elevating the patient's
leg to 60 degrees for 1 minute. Repetitive dorsiflexion and plantar
flexion of the foot may also precipitate pallor on the sole of the
foot when PAD is present. To qualitatively assess collateral blood
flow, the leg is then lowered as the patient moves to the seated position. This is done to elicit rubor, indicative of reactive hyperemia,
and determine pedal vein refill time. The time to development of
dependent rubor is indicative of the severity of PAD. Severe PAD
and poor collateral blood flow may prolong reactive hyperemia by
more than 30 seconds. Normally, pedal venous refill occurs in less
than 15 seconds. Moderate PAD subserved by collateral vessels is
suspected if venous refill is 30 to 45 seconds; severe disease with
poor collateral development is likely when venous filling time is
longer than 1 minute.
ULCERS
Ischemia arising from arterial occlusive disease or emboli may
cause formation of ischemic ulcers (see Chapter 60). They tend
to be small, annular, pale, and desiccated (Fig. 11-6) and are usu-
ally located in distal areas of the limbs (e.g., toes, heels, fingertips).
Ischemic ulcers vary in size but may be as small as 3 mm in diameter. Arterial ischemic ulcers are tender. Neurotrophic ulcers that
develop in patients with diabetes typically occur at sites of trauma,
such as areas of callus formation, bony prominence, or parts of the
foot exposed to mild chronic trauma caused by ill-fitting shoes.
Ischemic ulcers also develop in diabetic patients with PAD and
may have features of neuropathic ulcers. Without proper treatment,
ulceration may progress to tissue necrosis and gangrene. Gangrene
can be characterized as an area of dead tissue that blackens, mummifies, and sloughs.
FIGURE 11-6 Digital ulceration. Pernio is associated with persistent
sensation of cold, with pain in the toes. Painful blue nodules are noted in
association with a discrete ulcer.
DIGITAL VASOSPASM
It is unusual for patients with Raynaud phenomenon to present
to the physician's office during an attack in which the fingers are
blanched. Moreover, it is difficult to precipitate digital ischemia in
these patients, even with local cold exposure, such as placing the
hands in ice water. Digital ischemia may be apparent in patients with
fixed obstructive lesions of the digital arteries. Persistent digital ischemia may occur in patients with connective tissue disorders such
as scleroderma or systemic lupus erythematosus, atheroemboli, TAO,
or atherosclerosis. The fingers and toes are cool and appear cyanotic
or pale. Fissures, pits, ulcerations, or necrosis or gangrene may be
evident on the ischemic digits (see
Fig. 11-6).
LIVEDO RETICULARIS
Livedo reticularis can be described as a lacelike or netlike pattern
in the skin (
Fig. 11-7). The “laces” may vary in color from red to blue
and surround a central area of clearing. Cold exposure exacerbates the changes in hue. Both primary and secondary forms may
occur and may be complicated by ulceration. The primary benign
form is more common in women. The secondary forms are usually
associated with vasculitis, atheroemboli, hyperviscosity syndromes,
endocrine abnormalities, and infections. In the secondary forms
of livedo reticularis, lesions may be more diffuse and ominous.
Purpuric lesions and cutaneous nodules that progress to ulceration in response to cold may develop.
EDEMA
The limbs should be evaluated for edema. The most common location is in the legs, adjacent to the malleoli and over the tibia. With
deep digital palpation, development of a divot or finger impression
is indicative of pitting edema. Edema can be graded in each leg or
arm as absent, mild, moderate, or severe or on a numerical scale of
4, with 0 being the absence of edema. Unilateral edema may be evidence of DVT, chronic venous insufficiency, or lymphedema.
The most common physical findings of DVT include unilateral
leg swelling, warmth, and erythema. The affected vein may be tender. A common femoral vein cord is detected by palpating along
its course just below the inguinal ligament vein, and a femoral
vein cord would be appreciated along the anteromedial aspect of
the thigh. In the absence of obvious edema, a subtle clue may be
unilateral absence of contours of the thigh, calf, or ankle. Muscular
groups subtended by the thrombosed vein may be edematous due
to poor venous drainage, conferring a boggy feeling to the affected
calf or thigh muscles. Inflammation associated with a thrombosis
may make the leg feel warm.
FIGURE 11-7 Livedo reticularis. Note lacelike pattern of superficial skin
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vessels surrounding a clear area.
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CH
11
THE HISTORY AND PHYSICAL EXAMINATION
FIGURE 11-8 Skin changes of chronic venous insufficiency. Chronic
venous insufficiency and edema result in deposition of hemosiderin, causing
darkening and toughening of skin and giving calf a brawny appearance. Note
small superficial venous ulcers mid-calf above shin.
Homans sign is nonspecific and misses the diagnosis as commonly as it makes it. In John Homans's essay on lower extremity
venous thrombosis, he states, “The clinical signs of a deep thrombosis of the muscles of the calf are entirely lacking when the individual lies or even reclines in bed. It is possible there may be a little
discomfort upon forced dorsiflexion of the foot (tightening of the
posterior muscles) but it is not yet clear whether or not this is a sign
upon which to depend.”
19
Presence of thrombus just below the skin makes the diagnosis of
superficial thrombophlebitis relatively easy. The patient may present with local venous engorgement, a palpable cord, warmth, erythema, or tenderness.
CHRONIC VENOUS INSUFFICIENCY
With chronic venous insufficiency, the physical examination may
demonstrate fibrosis, tenderness, excoriation, and skin induration from
hyperkeratosis, cellulitis, and ulceration (
Fig. 11-8). Chronic venous
edema may impart hemosiderin deposition in the skin and confer
a brawny appearance, typically in the pretibial calf. The severity of
chronic venous disease may be classified using the CEAP (clinical signs,
e
tiology, anatomy, pathophysiology) classification20 (Table 11-1).
In contrast to arterial ulcers, which are circumscribed and pallid,
venous ulcers are large with irregular borders, erythematous, and
moist, giving the skin a shiny appearance. They are usually located
near the medial or lateral malleolus. Venous ulcers may be painless, but many are associated with pain.
21,22
VARICOSE VEINS
Varicose veins are dilated, serpentine, superficial veins. If they cluster,
they may feel and appear like a bunch of grapes (Fig. 11-9). Varicose
veins should be inspected and palpated. Areas of erythema, tenderness, or induration may identify superficial thrombophlebitis.
Varicose veins are most prominent with leg dependence (e.g., with
standing). Once filled, the veins may be balloted, and a fluid wave
may be detected. Venous telangiectasias, also known as spider veins,
TABLE 11-1 CEAP Clinical Classification
CLASS CLINICAL SIGNS
0 No visible or palpable signs of venous disease
1 Telangiectasis or reticular veins
2 Varicose veins
3 Edema
4 Skin changes ascribed to venous disease (e.g., pigmentation,
venous eczema, lipodermatosclerosis)
5 Skin changes as defined above, with healed ulceration
6 Skin changes as defined above, with active ulceration
CEAP, clinical signs, etiology, anatomy, pathophysiology.
are commonly confused with varicose veins. Spider veins are typically small, cutaneous veins in a caput medusa pattern.
Superficial venous varicosities may be primary or result from
deep venous thrombosis or insufficiency. An examiner can distinguish between superficial venous insufficiency and deep venous
insufficiency at the bedside using the Brodie-Trendelenburg test.
With the patient lying supine, the leg is elevated to 45 degrees and
a tourniquet applied after the veins have drained. The patient then
stands. The veins below the tourniquet should fill slowly. If venous
refill distal to the site of tourniquet application occurs in less than
30 seconds, this is evidence of an incompetent deep and perforator system. Slower refills suggest a competent deep and perforator
system. The varicose veins are examined upon tourniquet release.
Superficial venous insufficiency will be confirmed with rapid retrograde superficial venous filling.
The Perthes test can differentiate between deep venous insufficiency and a deep venous obstruction as the cause of varicose veins. The patient is asked to stand, and once the superficial
veins are engorged, a tourniquet is applied around the mid-thigh.
The patient then walks for 5 minutes. If the varicose veins collapse below the level of the tourniquet, the perforator veins are
14 6
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11
FIGURE 11-9 Varicose veins. Severe bilateral varicose veins with extension
into both feet.
presumed competent and the deep veins patent. If the superficial
veins remain engorged, either the superficial and/or communicating veins are incompetent. If the varicose veins increase in prominence, and walking causes leg pain, the deep veins are occluded.
LYMPHEDEMA
During the initial stages of lymphedema, leg swelling will be similar to venous insufficiency: soft and pitting. Extension of edema
into the foot to the origin of the toes may help differentiate lymphedema from venous edema (
Fig. 11-10). In addition, the inability to
pinch skin on the toes, the Stemmer sign, also may differentiate early
lymphedema from venous edema. Subsequently, the limb becomes
wooden as progressive deposition of protein-rich fluid causes induration and fibrosis of affected tissues. Lymphedema increases production of subcutaneous and adipose tissue, thickening the skin.
Advanced disease may be identified when the leg feels wooden,
edema is no longer pitting, and the limb is enlarged; the skin may
appear verrucous at the toes. Palpation for lymphadenopathy should
be performed when considering secondary causes of lymphedema.
LYMPHANGITIS
Lymphangitis can usually be visualized as a red streak that extends
proximally from an inciting lesion. If left untreated, the entire
limb may become edematous, erythematous, and warm, without
evidence of venous congestion or impairment of arterial flow.
Commonly, the regional lymph nodes are indurated.
Neck Examination
The neck is inspected for any areas of swelling or asymmetry.
Jugular venous pressure is assessed to investigate the possibility
of a volume overloaded state or congestive heart failure. Patients
typically are placed at 45 degrees and the height of jugular venous
pressure estimated. If necessary, the angle of head elevation should
be adjusted to see the top of the jugular venous column.
The carotid arteries are palpated between the trachea and
the sternocleidomastoid muscles. In older patients especially, the
carotid body may be sensitive, and carotid pulses may induce bradycardia and hypotension. Pulses should be symmetrical with a
rapid upstroke. Pulse asymmetry may indicate a proximal carotid
or brachiocephalic stenosis. Parvus and tardus pulses (decreased
amplitude and a delayed slow upstroke) may indicate aortic valve
stenosis or proximal occlusive disease. Stenosis of the carotid bifurcation or internal carotid artery usually does not affect carotid
pulse contour or amplitude. Occasionally, severe stenosis will create a thrill that can be appreciated by palpation.
The carotid pulses are auscultated to elicit evidence of bruits.
Bruits are caused by blood flow turbulence as a result of arterial
stenosis, extrinsic compression, aneurysmal dilation, or arteriovenous connection. The bell of the stethoscope is recommended
to appreciate low-frequency bruits and eliminate any adventitious sounds heard through the diaphragm. The entire cervical
portion of each carotid artery should be auscultated, including
the segment near the angle of the jaw where the carotid bifurcation is often located (
arteries for bruits is performed in the supraclavicular fossa and
between the lateral aspect of the clavicle and pectoralis muscle. Although the proximal location of a bruit defines the area
Fig. 11-11). Auscultation of the subclavian
FIGURE 11-10 Lymphedema. Extension of edema into foot to level of toe is
a useful physical sign to differentiate between venous edema and lymphedema.
Foot swelling ending abruptly at toes is called squared toe sign.
FIGURE 11-11 Auscultation of carotid artery. To appreciate low-tone
bruits, examiner should use stethoscope bell and apply mild to moderate
pressure. Entire length of artery should be examined, with particular attention
paid to region just below jaw, at approximation of carotid artery bifurcation.
of turbulent flow, a bruit may be appreciated for an additional
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several centimeters. The sensitivity and specificity of a carotid
bruit for the presence of stenosis ranges from 50% to 79% and
61% to 91%.
23
The pitch of bruits increases with worsening severity. Continuation of the bruit into diastole is another marker of
severity and implies advanced stenosis. Paradoxically, severe
stenosis causing subtotal arterial occlusion may not evoke an
audible bruit.
Abdominal Vascular Examination
Vascular examination of the abdomen is performed as the patient
lies supine on the examining table, with legs outstretched. From
this position, the abdominal wall should be relaxed and not rigid.
Prior to palpation, the abdomen should be inspected. Engorged
superficial veins in the abdomen indicate the possibility of inferior
vena cava obstruction. After inspection, all four quadrants are auscultated with the stethoscope. The presence of bruits is indicative
of aortic or branch vessel occlusive disease. Bruits may arise as a
result of mesenteric, renal, or aortic disease. Following auscultation,
the abdomen is palpated for masses and to detect an aortic aneurysm. Deepest palpation can generally be obtained by gradually
increasing pressure in the midline using both hands (
asthenic patients, the aorta can be palpated. In subjects with a waist
size greater than 40 inches, the likelihood of palpating an aneurysm
is quite limited.
FIGURE 11-12 Abdominal palpation for aneurysm. Examiner, using
progressively increasing force, palpates until aorta can be defined between both
sets of fingers. Examiner should appreciate lateral pulsation with every heart
beat. Aneurysm sizing is performed by estimating distance between closest
fingers of each hand.
Fig. 11-12). In
Presence of an aneurysm can be determined when there is a distinct and expansive pulsatile configuration to the aorta. An aneurysm should be sized by determining the lateral borders with both
hands, and the space estimated with a measuring tape. Tenderness
during the abdominal vascular examination is unusual and may
suggest aneurysmal expansion, an inflammatory aneurysm, or a
contained rupture. Nonaortic pathology, including appendicitis,
cholecystitis, diverticulitis, and peritonitis, are more common
causes of tenderness.
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THE HISTORY AND PHYSICAL EXAMINATION
CHAPTER
12 Vascular Laboratory Testing
Marie Gerhard-Herman, Joshua A. Beckman, Mark A. Creager
Vascular laboratory technology offers many cost-effective applications in the practice of vascular medicine.
includes both physiological testing and duplex ultrasonography.
Physiological testing includes segmental pressure measurements,
pulse volume recordings, continuous wave Doppler, and plethysmography. These tests employ sphygmomanometric cuffs, Doppler
instruments, and plethysmographic recording devices. Duplex
ultrasonography combines gray-scale and Doppler imaging with
spectral and color Doppler and is used for the majority of vascular laboratory tests. An ultrasound machine should be equipped
with vascular software and two transducers/probes, 5- to 12-MHz
transducers for the neck and extremities, and 2.25- to 3.5-MHz
transducers for the abdomen.
1
Vascular testing
Limb Pressure Measurement and Pulse
Volume Recordings
Limb segmental systolic blood pressure measurements and
pulse volume recordings are used to confirm a clinical diagnosis of peripheral artery disease (PAD) and further define the
level and extent of the obstruction. Segmental pressures are
typically measured in conjunction with segmental limb plethysmography (pulse volume recordings). These techniques are
used predominantly in the lower extremities, but are also applicable to the arms. Both procedures are performed using sphygmomanometric cuffs appropriately sized to the diameter of the
limb segment under study. The patient rests in the supine position for at least 10 minutes prior to measuring limb pressures.
Commercially available machines with automatic cuff inflation are able to digitally store the pressures and waveforms. A
continuous-wave (CW) Doppler instrument with a 4- to 8-MHz
transducer frequency is used to detect the arterial flow signal.
The cuff is quickly inflated to a suprasystolic pressure and then
slowly deflated until a flow signal occurs. The cuff pressure at
which the flow signal is detected is the systolic pressure in the
arterial segment beneath the cuff. For example, if the cuff is on
the high thigh and the sensor is over the posterior tibial artery
at the ankle, the measured pressure is reflective of the proximal
superficial and deep femoral arteries (DFAs) beneath the cuff, as
well as any collateral arteries, and not the posterior tibial artery.
The Doppler flow signal from an artery at the ankle is typically
used for all limb measurements. It is more accurate, although
less convenient, to place the Doppler transducer probe close to
the cuff being inflated.
Sphygmomanometric cuffs are positioned on each arm above
the antecubital fossa, on the upper portion of each thigh (high
thigh), on the lower portions of the thighs above the patella (low
thigh), on the calves below the tibial tubercle, and on the ankles
above the malleoli. Typically, foot pressures are measured by
insonating the posterior tibial and anterior tibial arteries at the
ankle level. Both arm pressures at the brachial artery are determined. A difference of greater than 20 mmHg between the arm
pressures indicates the presence of stenosis on the side of the
lower pressure. Pressure measurements are made at the high thigh,
low thigh, calf, and ankle levels with a tibial or dorsalis pedis signal selected as the flow indicator. A second method uses one long,
contoured thigh cuff rather than two separate thigh cuffs. The
lower-extremity pressure evaluation should begin at the ankle level
and proceed proximally. Patients who are found to have a normal
pressure measurement at rest may require a treadmill exercise test
to detect PAD. If disease distal to the ankle is suspected, pedal or
digital artery obstruction can be evaluated with cuffs sized appropriately for the toes.
Segmental Doppler Pressure Interpretation
Segmental limb pressures are compared with the highest arm
pressure. Ankle pressures are used to calculate the ankle-brachial
indices (ABI) for each extremity. This is accomplished by dividing
each of the ankle pressures by the higher of the brachial artery
pressures.
above 0.9 to 1.0 is borderline abnormal.
ABI in healthy subjects and patients with PAD confirmed by arteriography found that an ABI of 0.9 or lower was diagnostic of PAD
with 79% to 95% specificity and 96% to 100% sensitivity.
are compared between levels. A 20-mmHg or greater reduction in
pressures from one level to the next is considered significant and
indicates stenosis between those two levels. In healthy subjects,
the high thigh pressure determined by cuff typically exceeds the
brachial artery pressure by approximately 30 mmHg. A thigh/brachial index above 1 is interpreted as normal, and an index of 1 or
less indicates stenosis proximal to the thigh (
thigh pressures are low compared with arm pressure, the site of
obstruction could be in the aorta or ipsilateral iliac artery, common
femoral artery (CFA), or proximal superficial femoral artery (SFA)
(see
chial pressure, an ipsilateral iliofemoral artery stenosis is inferred.
cannot be determined because the vessels are noncompressible.
An index of 1.4 or greater suggests vascular calcification artifact
and makes interpretation of the pressure measurement unreliable.
Presence or absence of a significant pressure gradient cannot be
determined in the presence of vascular calcification artifact. In
this setting, the toe brachial index (TBI) is a useful measurement.
Toe brachial index is the ratio of the systolic pressure in the toe to
the brachial artery systolic pressure. This should be performed in a
warm room; cold-induced vasospasm may lower the digital pressure. To perform the procedure, a cuff is placed on a toe. Typically, the
great toe is used. The pulse waveform is obtained by photoplethysmography or Doppler. The cuff is inflated to suprasystolic pressure
and then deflated. Systolic pressure is determined as the pressure at
which the waveform reappears. A normal value for TBI is 0.70.
2
A normal ABI is between 1.0 and 1.4, whereas an ABI
Fig. 12-1). If only one high thigh pressure is less than the bra-
In the presence of severe vascular calcification, systolic pressures
3
Studies that evaluated the
4
Pressures
Fig. 12-1). When high
Pulse Volume Recording Interpretation
The same cuffs used to measure segmental pressures may be
attached to a plethysmographic instrument and used to record
the change in volume of a limb segment with each pulse, designated the pulse volume. Pulse volume waveform evaluation
allows assessment of arterial flow in regions of calcified vessels
because the test does not rely on cuff occlusion of the calcified
5
artery.
Each cuff is inflated in sequence to a predetermined reference pressure up to 65 mmHg. The change in volume in the limb
segment causes a corresponding change in pressure in the cuff
throughout the cardiac cycle. Interpretation of the pulse volume
recording (PVR) requires calibration of the amount of air in the
cuff.
A pulse volume waveform is recorded for each limb segment.
Pulse volume recording analysis is based on evaluation of waveform shape, signal, and amplitude (
the normal pulse volume waveform resembles the arterial pressure waveform, and is composed of a sharp systolic upstroke followed by a downstroke that contains a prominent dicrotic notch. A
hemodynamically significant stenosis manifests as a change in the
PVR contour toward a tardus parvus waveform. Both the slope and
amplitude decrease when there is more severe disease. Severity of
PAD can be defined by the slope of the upstroke and amplitude of
the pulse volume (see
Fig. 12-2).
Fig. 12-2). The configuration of
14 8
PVR 66 mmHg 747cc RIGHT High Thigh
Segmental pressure
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Gain: .75 mmHg/20mm Spd: 25 Amp: 16
PVR 68 mmHg 832cc RIGHT Above Knee
Gain: .75 mmHg/20mm Spd: 25 Amp: 15
and PVR study
Brachial
Right
165
1.08 178 129 0.78
1.06 175 116 0.70
0.83 137 115 0.70
Right Left
0.85 141 111DP 0.67
0.85
140 100PT 0.61
Left
162
PVR 67 mmHg 557cc LEFT High Thigh
Gain: .75 mmHg/20mm Spd: 25 Amp: 25
PVR 66 mmHg 506cc LEFT Above Knee
Gain: .75 mmHg/20mm Spd: 25 Amp: 27
149
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VASCULAR LABORATORY TESTING
VASCULAR LABORATORY TESTING
PVR 64 mmHg 256cc RIGHT Below Knee
Gain: .75 mmHg/20mm Spd: 25 Amp: 40
PVR 65 mmHg 179cc RIGHT Ankle
Gain: .75 mmHg/20mm Spd: 25 Amp: 35
PVR 56 mmHg 61cc RIGHT Metatarsal
Gain: .75 mmHg/20mm Spd: 25 Amp: 13
FIGURE 12-1 Segmental pressure measurements and pulse volume recording (PVR). Right leg has a pressure drop between low thigh and calf consistent with
superficial femoral/popliteal artery stenosis. Left leg has a pressure drop at level of high thigh consistent with iliofemoral artery stenosis. ABI, ankle-brachial index.
Pulse waveforms can also be obtained using photoplethysmography, recording reflected infrared light. In photoplethysmography, the signal is proportional to the quantity of red blood cells in
the cutaneous circulation; it does not measure volume changes.
Waveform shape is assessed in a similar fashion in pulse volume
and photoplethysmography recordings. Low photoplethysmographic waveforms in the toes identify increased risk of amputation, in addition to the toe pressure.
5
ABI: 0.85 ABI: 0.67
shortness of breath with minimal exertion, or unstable angina. The
test cannot be performed if the patient cannot walk on a treadmill.
Patients are instructed to fast for 12 hours prior to walking on the
treadmill. The constant-load treadmill test is performed at a speed
of 2 mph and an incline of 12%. Graded exercise protocols increase
the grade and/or speed in 2- to 3-minute stages. The Gardner protocol is the most commonly used graded protocol to evaluate walking exercise capacity.
PVR 63 mmHg 237cc LEFT Below Knee
Gain: .75 mmHg/20mm Spd: 25 Amp: 30
PVR 65 mmHg 165cc LEFT Ankle
Gain: .75 mmHg/20mm Spd: 25 Amp: 23
PVR 54 mmHg 56cc LEFT Metatarsal
Gain: .75 mmHg/20mm Spd: 25 Amp: 13
7
It begins at a speed of 2 mph and an incline
of 0%, and the grade progressively increases by 2% every 2 minutes,
Exercise Testing for Peripheral Artery Disease
Exercise testing is an adjunctive physiological test to evaluate
PAD. It is useful to assess functional capacity and determine the
distance patients with claudication are able to walk. Moreover,
it can be used to clarify whether leg symptoms are related to
PAD. This is relevant in patients with symptoms that are atypical
for claudication and in those who have a history of intermittent
claudication, yet normal ABIs at rest.
to treadmill exercise testing for PAD include rest pain in the leg,
6
Relative contraindications
allowing for a wider range of responses to be measured. It is often
used to determine clinical trial end points such as change in walking time in response to therapy. Other graded exercise protocols,
such as the Bruce protocol, are not commonly used because the
rapid rate of speed and incline limits assessment of exercise capacity in claudicants.
The treadmill exercise test is terminated when the patient cannot
continue owing to leg claudication or chest pain, or is limited by
other symptoms such as shortness of breath or fatigue. The patient
then immediately lies down on the stretcher. Ankle pressures are
150
Pr
Normal
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12
FIGURE 12-2 Pulse volume recording (PVR). Normal waveform has a sharp
upstroke, dicrotic notch, and a period of diastasis. Mildly abnormal waveform
has a delay in upstroke and a straightened downslope (blue line). Moderately
abnormal waveform has a delay in upstroke (blue line), flat systolic peak, and
diminished amplitude. Severely abnormal waveform has a flat systolic peak and
very diminished amplitude.
Mild
Moderate
Severe
obtained starting with the symptomatic leg, followed by the highest brachial pressure. Pressures are repeated approximately every
1 to 2 minutes until they return to baseline. Data recorded from
the exercise test should include ankle pressures, length of time the
patient was able to walk, time required for pressures to return to
baseline, nature and location of the patient's symptoms, and reason for discontinuing the test. A decrease in ABI of more than
20% immediately following exercise is diagnostic for PAD. The
time before ankle pressure returns to normal is increased in more
severe disease (e.g., from 1 minute in mild disease to 10 minutes in
more severe disease).
Transcutaneous Oximetry
By exploiting variations in color absorbance of oxygenated and
deoxygenated hemoglobin (Hb), transcutaneous oximetry can
determine the state of blood oxygenation. Oximeters use two light
frequencies, red at 600 to 750 nm and infrared at 800 to 1050 nm,
to differentiate oxygenated and deoxygenated Hb. Deoxygenated
blood absorbs more red light, whereas oxygenated blood absorbs
more infrared light. Oximeters typically employ both an emitter
and receiver. Red and infrared light is emitted and passes through
a relatively translucent structure such as the finger or earlobe.
A photodetector determines the ratio of red and infrared light
received to derive blood oxygenation. When measured continuously, oxygenation peaks with each heartbeat as fresh oxygenated blood arrives in the zone of measurement. Normal values
for oxygen tension are from 50 to 75 mmHg. One probe is placed
on the chest as a control to ensure that oxygen tension is from
50 to 75 mmHg. A second probe is placed on the limb in the area
of interest. Measurements are obtained from the probe, which is
sequentially positioned from proximal to distal segments of the
limb. Normal limb Tc
Transcutaneous oximetry is most often used to determine the
o
should approximate that of the chest.
2
level of amputation. A value above 20 mmHg can predict healing
at the site with 80% accuracy.7 This measurement is not affected by
arterial calcification.
Physical Principles of Ultrasonography
Ultrasound Image Creation
An ultrasound transducer, or probe, emits sound waves in discrete
bundles or pulses into the tissue of interest. On encountering a
tissue, a portion of the waves is reflected back to the transducer.
The fraction of returning waves depends on density and size of
the tissue examined. The depth of tissue is determined by the
time required for pulse emission and return. Thus, by integrating
the number of returning pulses and the time required for return,
a B-mode, or gray-scale image may be created. The time for wave
reflection decreases with higher ultrasound probe frequencies.
Transducer probes with higher frequencies image superficial
tissues better than probes with lower frequencies, but lose depth
imaging because of attenuation of the returning emitted pulses.
Improvements in technology have permitted band-width widening of vascular transducers, facilitating analysis of harmonics of the
fundamental frequency. A harmonic represents a whole-number
multiple of the emitted frequency. Because the tissue compresses
and expands in response to the application of ultrasound, the fundamental wave may become distorted, impairing image quality.
The distortion, however, also creates harmonics of the original
frequency that can be detected by the transducer. By detecting
only the fundamental frequency and its harmonics, artifact such
as speckle and reverberation may be reduced to create a clearer
image.
Detection of Blood Flow
Normal blood flow is laminar in a straight segment of an artery.
If thought of as a telescopic series of flow rings, blood moves forward most rapidly in the middle ring, and velocity decreases in the
outer rings as blood comes closer to the vessel wall. The cardiac
cycle, defined by its pulsatile nature of flow, causes a continual
variation in blood flow velocity, highest with systole and lowest
with diastole. The concentric or laminar flow of blood may be disturbed at a normal branching point or with abnormal vessel contours, such as those caused by atherosclerotic plaque. Disturbed
or turbulent flow causes a much greater loss of pressure than
laminar flow.
Determining flow velocity is a mainstay of vascular ultrasonography. Abnormalities in the vessel wall cause changes in flow
velocity and permit detection and assessment of stenotic regions
within the vessel. Flow in a normal vessel is proportional to the
difference of pressure between the proximal and distal end of the
vessel. The prime determinant or limitation of flow is the radius
of the vessel because volume of blood flow is determined by the
fourth power of the radius. For example, a 50% reduction in vessel
radius causes a greater than 90% reduction in blood flow. Thus,
blood flow represents an example of Poiseuille's law, which determines flow of a viscous fluid through a tube. Specifically,
8L
η
4
π×∆ ×
Q
=
where Q denotes volume of flow, D P is pressure at inflow minus the
pressure at outflow, r is the radius, h is viscosity, and L is tube length.
Because blood viscosity, blood vessel length, and pressure remain
relatively stable, the most important determinant of blood flow is
vessel lumen size.
Vascular ultrasonography can depict flow velocity by taking
advantage of Doppler shift frequencies. Frequency will shift either
positively or negatively, depending on direction of blood flow.
Variables that determine the size of the shift include the speed
of sound, speed of the moving object, and angle between the
transmitted beam and moving object. Christoph Doppler described
No frequency shift
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this relationship using the following equation:
F (2 F ·V·cos ) c
dt
where F
transmitted from the probe, V is the velocity of flow, cos is the
is the Doppler frequency shift, Ft is the Doppler frequency
d
θ ÷=
cosine, q is the angle between the beam and direction of the moving
object, and c is the velocity of sound.
Artifact
Although a highly reliable imaging modality, ultrasound does suffer from occasional image artifact.
calcium deposits permit few sound waves to penetrate, resulting
in acoustic shadowing and diminishing imaging of deeper tissues.
Tissue imaging enhancement may be noted on the far side of echofree or liquid-filled zones. Tissue interfaces may generate multiple
sound wave reflections, causing “additions” to the tissue termed
reverberation artifact. Refraction of the sound pulse may cause
improper placement of a structure of an image and shadowing at
the edge of a large structure. Highly reflective surfaces may create mirror images because the reflecting tissue alters the timing of
the returning sound wave. The mirror image should be equidistant
from the reflecting surface or tissue.
8
Dense objects like vessel-wall
Gray-Scale (B Mode) Imaging
Ultrasound images are generated using a pulse echo system. The
position of the tissue interface is determined by the time between
pulse generation and returning echo. Each returning echo is
displayed as a gray dot on a video screen using a brightness mode
(B mode) in which the brightness of the dot depends on the
strength of the reflected wave. A two-dimensional (2D) image is
created by sequentially transmitting waves in multiple directions
within a single plane and combining the reflected echoes into a
single display. The image can be refreshed rapidly, permitting realtime display of the gray-scale image. The surface of interest should
be perpendicular to the ultrasound beam to obtain the brightest
echo with B-mode imaging. This is readily achieved in vascular
imaging because the neck, extremity, and visceral vessels generally lie parallel to the surface of the transducer. Higher-frequency
probes are used to image vessels close to the surface, and lowerfrequency probes are used to image deeper vessels. Details of the
vessel wall can be seen more clearly with the use of harmonics. The
wide band width of transducers allows analysis of returning harmonics (whole-number multiples) of the fundamental frequency.
Spectral Doppler Waveform Analysis
Velocity recordings are obtained with an angle of 60 degrees
between the Doppler insonation beam and the flow. In ultrasound
practice, the optimal angle of measurement between the beam
and blood flow is 60 degrees. Although maximal shift is detected
at 0 degrees, this angle cannot be reliably obtained in vascular
imaging because the vessels are parallel to the surface of the body.
Insonation angles below and above 60 degrees influence the measurement such that small reductions in the insonation angle may
alter velocity by 10%, whereas small increases in insonation angle
may change flow velocity by 25% (
volume cursor is placed parallel to the inner wall, and a Doppler
angle from 30 to 60 degrees between the wall and the insonation
beam (or flow jet) is used. A normal peripheral artery Doppler
waveform consists of a narrow, sharply defined tracing. This indicates that all blood cells are moving at an equivalent speed at
any time in the cardiac cycle.
as high resistance due to limited flow during diastole (e.g., normal peripheral arterial Doppler velocity waveform), or low resistance with continuous flow during diastole, as when downstream
resistance arterioles are widely dilated or there is contiguity with
Fig. 12-3). Thus, the sample-
11
Waveforms are also characterized
9,10
90°
V=(Fd·c)/2Ft cos θ)
FIGURE 12-3 Doppler angle is the angle between insonation beam and
sample cursor aligned with flow. Dashed lines represent different insonation
beams. Solid arrow represents direction of flow and position of Doppler sample
cursor. Velocity is determined using the Doppler equation, with the cosine
(cos) in the denominator. The cos θ degrees = 1, cos 30 degrees = 0.86, cos
60 degrees = 0.5, and cos 90 degrees = 0. c, velocity of sound; Fd, Doppler
frequency shift; Ft, transmitted Doppler frequency; V, velocity.
High resistance
Low resistance
FIGURE 12-4 High- and low-resistance waveforms. These two waveforms
are distinguished by the absence (high resistance) and presence (low resistance)
of flow during diastole.
50% of maximal shift60°
30°
0°
low-resistance circuits (e.g., normal internal carotid artery [ICA]
velocity waveform) (
Fig. 12-4). The normal high resistance wave-
form is typically triphasic. The first component is caused by initial high-velocity forward flow during ventricular systole. A range
of normal peak systolic velocity (PSV) measurements have been
12
defined
for each arterial segment, described later in this chapter.
The second phase of the waveform consists of early diastolic flow
reversal as left ventricular (LV) pressure falls below aortic pressure
prior to aortic valve closure.
13
The final or third component is a small
amount of forward flow when there is elastic recoil of vessel walls.
Flow is typically not uniform or laminar at bifurcations and sites of
stenosis; at these sites flow becomes turbulent. For these locations,
the spectral Doppler waveform reflects the fact that blood cells
move with varying velocities. Instead of a narrow well-defined tracing (see
Fig. 12-4), spectral broadening becomes evident (Fig. 12-5) ,
with partial or complete filling-in of the area under the spectral
waveform. This third, or late, diastolic component is usually absent
in atherosclerotic vessels that have lost compliance or elasticity.
Color Doppler
Color Doppler is the phase or frequency shift information contained in the returning echoes and processed in real time to form
a velocity map over the entire imaging field.
shift data are available for every point imaged. This information
is then superimposed on the gray-scale image to provide a composite real-time display of both anatomy and flow. When motion
is detected, it is assigned a color, typically red or blue, determined
by whether the frequency shift is toward or away from the probe.
Color assignment is arbitrary and can be altered by the user, but
most choose to assign the color red to arteries and blue to veins.
With increasing Doppler frequency shifts, the hue and intensity of
the color display change, with progressive desaturation of the color
and a shift toward white at the highest detectable velocities.
14
Doppler frequency-
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