I
ATRIAL FIBRILLATION
Intermittent
claudication
(a cramplike
pain on walking)
is often the first
symptom of atherosclerosis in the leg
arteries. If the condition is associated
with an inherited lipid disorder (see
hyperlipidaemias),
fatty
deposits
may
develop on tendons or as visible lumps
under the skin.
DIAGNOSIS AND TREATMENT
Blood flow through an artery can be
investigated by
angiography
(X-rays after
injection of a
radiopaque
substance) or
Doppler
ultrasound scanning
The best treatment for atherosclerosis
is to prevent it from progressing by the
maintenance of a healthy lifestyle. This
includes adoption of a low-fat diet, not
smoking, regular exercise, and main-
tenance of the recommended weight
for height. These measures lead to a
reduced risk of developing significant
atherosclerosis.
Those individuals found to have high
blood cholesterol levels but who are
otherwise
in
good
health
will
be
advised to adopt a low-fat diet. They
may also be given drugs that decrease
blood cholesterol levels (see
lipid-lower-
ing drugs).
For people who have had a
heart attack, research has shown that
there may be a benefit in lowering
blood cholesterol levels, even if the
level is within the average range for
healthy people.
People with atherosclerosis and those
at risk may be prescribed a drug such as
aspirin
to reduce the risk of blood clots
forming on the damaged artery lining.
Surgical treatment of atherosclerosis,
such as coronary angioplasty (see
angio-
plasty, balloon),
may be recommended
for those people thought to be at high
risk of severe complications. If blood
flow to the heart is severely obstructed,
a
coronary artery bypass
may be carried
out to restore blood flow.
athetosis
A disorder of the nervous system that
is characterized by involuntary slow,
writhing movements, most often of the
face,
head,
neck,
and
limbs. These
movements commonly include facial
grimacing,
with
contortions
of the
mouth. There may also be difficulty in
balancing and walking.
Athetosis tends to be combined with
chorea
(involuntary
irregular,
jerky
movements). Both athetosis and chorea
arise from damage to the
basal ganglia
,
clusters of nerve cells in the brain that
control movement.
Causes of athetosis include brain dam-
age prior to or at birth (see
cerebral
palsy),
encephalitis
(brain
infection),
degenerative disorders such as
Hunting-
ton’s disease,
or as a side effect of
phenothiazine drugs
or
levodopa.
If drug
treatment is the cause of the condition,
the
abnormal movements
may stop
when the drug is withdrawn.
athlete’s foot
A common condition in which the skin
between the toes becomes itchy and
sore and may crack, peel, or blister.
Athlete’s foot
The typical appearance of athlete’s foot is of
fissuring in the cleft between the fourth and fifth
toes. There is usually an annoying itch.
muscles may become atonic after injury
to the
brachial plexus
(nerve roots in the
neck passing into the arm).
atopic eczema
Atopic
eczema
is the most common
form of eczema (an inflammatory skin
condition). It usually begins in infancy
but may flare up during adolescence and
adulthood. The cause of atopic eczema
is unknown, but people with
atopy
(a
predisposition to allergic reactions) are
more susceptible.
atopy
A predisposition to various allergic reac-
tions (see
allergy).
Atopic individuals
have a tendency to suffer from one or
more allergic disorders, such as
asthma
,
eczema
,
urticaria
(nettle rash), and aller-
gic
rhinitis
(hay fever).
The mechanism that underlies the
predisposition
is
unclear,
but
atopy
seems to run in families.
ATP
An
abbreviation
for
the
compound
adenosine
triphosphate,
the
principal
energy-carrying chemical in the body.
(See also
ADP; metabolism.)
CAUSES
Athlete’s foot is usually the result of a
fungal infection known medically as
tinea pedis, but the condition may also
be caused by bacteria.
Because the fungi thrive in humid
conditions, athlete’s foot is more com-
mon in people with particularly sweaty
feet and those who wear shoes and
socks
made
from
synthetic
fibres,
which do not absorb sweat.
TREATMENT
Self-treatment with topical
antifungal
drugs
is usually effective and should be
combined with careful washing and
drying of the feet.
atlas
The topmost cervical
vertebra
in the
human
spine.
The atlas is attached to
and supports the skull. A pivot joint
attaching the atlas to the second cervical
vertebra, the
axis,
allows the atlas to
rotate, thereby turning the head from
side to side.
atony
Loss of tension in a muscle, so that it is
completely flaccid. Atony can occur in
some nervous system disorders or after
injury to nerves. For example, the arm
atresia
Congenital
(present from birth) absence
or severe narrowing of a body opening
or tubular organ due to a failure of
development in the uterus. Examples
are
biliary atresia,
in which the bile ducts
between the liver and duodenum are
absent;
oesophageal atresia,
in which the
oesophagus comes to a blind end; and
anal atresia (see
anus, imperforate),
in
which the anal canal is shut off. Most
forms of atresia require surgical correc-
tion early in life.
atrial fibrillation
A type of abnormality of the heartbeat
(see
arrhythmia
,
cardiac
) in which the
atria (see
atrium
), the upper chambers
of the heart, beat irregularly and very
rapidly. The
ventricles
(the heart’s lower
chambers) also beat irregularly but at a
slower rate. As a result, the pumping
ability of the heart is reduced.
CAUSES
Atrial fibrillation can occur in almost
any longstanding heart disease, but it is
most often associated with
heart-valve
disorders or
coronary artery disease.
SYMPTOMS AND SIGNS
Sudden onset of atrial fibrillation can
cause
palpitations
(awareness of a fast
A
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