| Peripheral
Arterial Disease
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What
is peripheral arterial disease?
The term peripheral arterial disease is
used to describe damage to the peripheral arteries which is often caused
by arterial hypertension and/or the formation of plaques of cholesterol,
platelets, fibrin, and other substances on the arterial walls, and leads
to progressive degrees of blockage and constriction of the arterial
circulation. Where arteries are blocked by cholesterol deposits the
condition is known as 'Atherosclerosis' and where mineral deposits are
also forming plaque the condition is known as 'arteriosclerosis'.
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Known
causes
The known causes of peripheral arterial disease include smoking, high
cholesterol levels (diet), high blood pressure as well as hereditary
susceptibility (ie. strong family history of similar disease) and diabetes
.
There are various possible causes
for arteriosclerosis but by far the most common cause is the deposition of
plaques of cholesterol (known as atherosclerosis), platelets and other
substances within the arterial walls. Sometimes the build-up is very
gradual, but in other cases the build-up is suddenly increased as a chunk
of matter breaks off and suddenly blocks the already narrowed opening. In
this case, diet is a primary factor to be considered (see below - Diet
& Nutrition).
Causative Factors summarised
There are several factors which may
influence the strength and functioning of the arteries as well as the
build-up of plaque on the arterial walls. These include:-
1. Hereditary factors (ie. a strong
family history of heart attacks)
2. Being male - females are less likely to suffer peripheral arterial
disease, probably because the female hormones offer some degree of
protection.
3. Cigarette smoking and high blood pressure - both of which are
reversible in most cases.
4. High blood cholesterol levels (both total and low density types).
5. Risk increases with age.
6. Certain intense, hostile or time- pressured personality types (so-
called type A), inactive lifestyle, and high cholesterol diets.
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Symptoms
A blockage in the arteries can occur
anywhere in the body although the most common site is the arteries of the
legs, either high in their course in the pelvis, or further down in the
calf. Once blockage becomes severe, exertion of the muscles which receive
blood supply from the affected artery causes pain due to insufficient
blood. This is known as intermittent claudication and often causes an
aching pain in the muscle which is relieved by rest and worsened by
resumed physical activity. If pain is present even at rest, the problem is
serious and unless treated, could necessitate amputation of the limb.
In the very severe and advanced
stages, the limb becomes cold, pale, discoloured, and sores form on the
skin from gangrene to the area involved. Infection may set in, and
ultimately the leg must be amputated to save the life of the patient.
It is unusual for other areas to be
affected without the legs being involved, but those with arteriosclerosis
in the leg, have a much higher incidence of heart disease, stroke, and
kidney artery blockage.
If the arteries in the brain are
affected, this can lead to a stroke. Where coronary arteries are affected,
this will cause angina (chest pain) or even heart attack.
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Diagnosis
Apart from the above symptoms,
arteriosclerosis has other typical signs including absent pulses andpoor
skin filling from capillaries which are compressed. Ultrasound tests may
further confirm the diagnosis, but anarteriography in which a dye is
injected into the larger arteries and traced with X-rays is the most
reliable test.
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Conventional
Treatment
Typical medical treatment ranges from
light exercise (if no major symptoms are evident) and drug therapy to
surgery. Bypass grafts made of synthetic material is inserted in place of
the blocked segments; alternatively, the area involved may be surgically
dilated.
If the blockage is in many smaller
vessels instead of one or a few large vessels, surgery is considered
inappropriate but if a single severe blockage is present, a procedure
called "balloon dilatation" is sometimes advised. In this mode
of treatment, a tube is inserted into the artery under x-ray guidance, and
at the area of obstruction a tiny balloon is inflated to relieve the
obstruction.
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Drug
Therapy
Medications are often prescribed to
control the symptoms relating to arteriosclerosis. The oldest and most
common agents are the nitrates, derivatives of nitroglycerine. They
include nitroglycerine, isosorbide, and similar agents. Newer forms
include long acting oral agents, plus skin patches which release a small
amount through the skin into the bloodstream over a full day. They act by
reducing the burden of blood returning to the heart from the veins and
also by dilating the coronary arteries themselves. Nitrates are considered
by many to be the mainstay of medical therapy for angina, and are used
both for treatment of symptoms as well as prevention of anticipated
symptoms. They are considered to be effective for relief and prevention of
angina, and sometimes for limiting the size of a heart attack. However,
there are side effects associated with these drugs including headaches,
dizziness, postural hypotension and tachycardia (1).
The second group of drugs are called
"beta blockers" for their ability to block the activity of the
beta receptors of the nervous system. The beta receptors cause blood
pressure elevation, rapid heart rate, and forceful heart contractions.
When these actions are decreased, the heart needs less blood, and thus
angina and even the extent of a heart attack may be reduced. Again, these
drugs have known possible side effects including gastro-intestinal
disturbances and incredibly, heart failure! (2).
The latest group of drugs for
coronary disease is called the calcium channel blockers. Calcium channels
refer to the areas of the membranes of heart and other cells where calcium
flows in and out, reacting with other chemicals to modulate the force and
rate of contractions. In the heart, they can reduce the force and rate of
contractions and electrical excitability, thereby having a calming effect
on the heart. These drugs also have known side effects including oedema,
liver and kidney damage, headache, nausea and rashes (3).
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Bypass
Surgery
If coronary arteries become affected,
by-pass surgery is often undertaken. However, xperts who reviewed bypass
surgery over a 15 year period concluded that, in most cases, the operation
has not been shown to save lives. In fact, they found that, quite the
contrary, there is a 15% (or greater) risk of brain damage following
coronary bypass surgery(4).
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Prognosis
If peripheral arterial disease is left
untreated it can be fatal by leading to a stroke or heart attack (where
the coronary arteries are affected.) Especial caution is needed if a
patient is also diabetic because the disease can progress very rapidly in
diabetic patients.
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The
use of Aspirin
Aspirin has been shown to help thin the blood and thereby reduce pressure
on the heart and helping to prevent heart disease, BUT at the same time,
it also increases the likelihood of arterial stroke (5).
(1) British National
Formulary
(2) British National Formulary
(3) British National Formulary
(4) H McIntosh 'The first decade of aortocoronary bypass grafting 1967-77
A review', Circulation 57 (1978):405 G Kolata 'Consensus on Bypass
Surgery-Indications and Limitations' Lancet 2 (1980):511 'Brain
Damage after Open Heart Surgery' Lancet 1 (1982):1161
(5) Clarke JTR et al, 'Increased incidence of epistaxis in adolescents
with familial hypercholesterolemia treated with fish oil' Journal of
Paediatrics Jan 1990, 116 (1)
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