C h a p t e r 1 8
Disorders of Blood Flow and Blood Pressure
415
Arterial Disease of the Extremities
Disorders of the circulation in the extremities often are
referred to as
peripheral vascular disorders.
17
In many
respects, the disorders that affect arteries in the extremi-
ties are the same as those affecting the coronary and
cerebral arteries in that they produce ischemia, pain,
impaired function, and in some cases infarction and tis-
sue necrosis. Not only are the effects similar, but the
pathologic conditions that impair circulation in the
extremities are also identical. This section focuses on
peripheral arterial disease, thromboangiitis obliterans,
and Raynaud phenomenon.
Peripheral Arterial Disease
Peripheral artery disease (PAD) refers to the obstruc-
tion of large arteries that supply the body’s peripheral
structures rather than its central structures such as the
heart or brain. Often PAD is a term used to refer to ath-
erosclerotic blockages found in the lower extremities.
Peripheral artery disease can result from atherosclerosis,
inflammatory processes leading to stenosis, embolism,
or thrombus formation. It causes either acute or chronic
ischemia. The disease is seen most commonly in men in
their 60s and 70s. The risk factors for PAD are similar
to those for coronary artery disease. Cigarette smoking
and diabetes mellitus are the strongest risk factors, with
more than 80% of persons with the disorder being cur-
rent or former smokers.
17
As with atherosclerosis in other locations, the signs
and symptoms of vessel occlusion are gradual. The pri-
mary symptom of chronic obstructive arterial disease is
pain with walking or
claudication
(from the Latin verb
claudicare, “to limp”).
18
Typically, persons with the dis-
order complain of calf pain because the gastrocnemius
muscle has the highest oxygen consumption of any mus-
cle group in the leg during walking. Some persons may
complain of a vague aching feeling or numbness, rather
than pain. Other activities such as swimming, bicycling,
and climbing stairs use other muscle groups and may not
incite the same degree of discomfort as walking. Other
signs of ischemia include atrophic changes and thinning
of the skin and subcutaneous tissues of the lower leg and
diminution in the size of the leg muscles. The foot often
is cool, and the popliteal and pedal pulses are weak or
absent. Limb color blanches with elevation of the leg
because of the effects of gravity on perfusion pressure
and becomes deep red when the leg is in the dependent
position because of an autoregulatory increase in blood
flow and a gravitational increase in perfusion pressure.
When blood flow is reduced to the extent that it no lon-
ger meets the minimal needs of resting muscle and nerves,
ischemic pain at rest, ulceration, and gangrene develop.
As tissue necrosis develops there typically is severe pain
in the region of skin breakdown, which is worse at night
with limb elevation and is improved with standing.
Diagnostic methods include inspection of the limbs
for signs of chronic low-grade ischemia such as subcuta-
neous atrophy, brittle toenails, hair loss, pallor, coolness,
or dependent rubor. Palpation of the femoral, popliteal,
posterior tibial, and dorsalis pedis pulses allows for an
estimation of the level and degree of obstruction. The
ratio of ankle to arm (i.e., tibial and brachial arter-
ies) systolic blood pressure is used to detect significant
obstruction, with a ratio of less than 0.9 indicating
occlusion. Blood pressures may be taken at various lev-
els on the leg to determine the level of obstruction. A
Doppler ultrasound stethoscope may be used for detect-
ing pulses and measuring blood pressure. Ultrasound
imaging, magnetic resonance imaging (MRI) arteriogra-
phy, spiral computed tomographic (CT) arteriography,
and invasive contrast angiography also may be used as
diagnostic methods.
17,18
Treatment includes measures directed at protection
of the affected tissues and preservation of functional
capacity. Walking (slowly) to the point of claudica-
tion usually is encouraged because it increases col-
lateral circulation. Avoidance of injury is important
because tissues of extremities affected by atherosclero-
sis are easily injured and slow to heal. It is important
to address other cardiovascular risk factors such as
smoking, hypertension, hyperlipidemia, and diabetes.
Drug therapy includes antiplatelet therapy (e.g., aspi-
rin or clopidogrel). Other medications that are useful
include statins, cilostazol (a vasodilator with antiplate-
let properties), and pentoxifylline (an antiplatelet agent
that decreases blood viscosity and improves erythrocyte
flexibility). Percutaneous or surgical intervention is typi-
cally reserved for the patient with disabling claudication
or limb-threatening ischemia. Surgery (i.e., femoropop-
liteal bypass grafting using a section of saphenous vein)
may be indicated in severe cases. Percutaneous translu-
minal angioplasty and stent placement, in which a bal-
loon catheter is inserted into the area of stenosis and the
balloon inflated to increase vessel diameter, is another
form of treatment.
17,18
Thromboangiitis Obliterans
Thromboangiitis obliterans, also known as
Buerger
disease
, is a recurring progressive, nonatherosclerotic
inflammation and thrombosis of small and medium-
sized arteries and veins, usually the plantar and digital
vessels in the foot and lower leg.
1,2,19,20
Arteries in the
arm and hand also may be affected. Although primar-
ily an arterial disorder, the inflammatory process often
extends to involve adjacent veins and nerves. Usually it
is a disease of young, heavy cigarette smokers, occurring
before the age of 35. The pathogenesis of Buerger disease
remains elusive, though cigarette smoking and in some
instances tobacco chewing seem to be involved. It has
been suggested that the tobacco may trigger an immune
response in susceptible persons or it may unmask a clot-
ting defect, either of which could incite an inflammatory
reaction of the vessel wall.
19
It is more common in the
Mediterranean region, Middle East, and Asia.
1,2
Pain is the predominant symptom of the disorder. It
usually is related to distal arterial ischemia. During the
early stages of the disease, there is intermittent claudi-
cation in the arch of the foot and the digits. In severe
cases, pain is present even when the person is at rest.
