CORSET
treated
according
to
their
cause. A
superficial, noninfectious ulcer usually
heals quickly; if it fails to do so, it may
be treated with a “bandage’’ contact
lens or with
tarsorrhaphy
(temporary
sealing of the eyelids).
coronary
Any structure that encircles another like
a crown. The term is usually used to
refer to the
coronary arteries,
w hich sur-
round the heart and supply it with
blood It is also sometimes used as a
nonmedical term for a heart attack (see
myocardial infarction).
coronary artery
Either of the two main
arteries
that sup-
ply the heart tissues with oxygen-rich
blood. These vessels, known as the left
and right main coronary arteries, arise
directly from the
aorta
(the main artery
in
the
body). The
term
“ coronary
artery” is also applied to any of the
arteries that branch off from the main
coronary arteries, such as the left cir-
cumflex artery and the left anterior
descending artery. Blockage of a coron-
ary artery as a result of
atherosclerosis
(an accumulation of fatty deposits in
the artery) can lead to
myocardial infarc-
tion.
(See also
coronary artery disease.)
coronary artery bypass
A major heart operation that is carried
out in order to bypass
coronary arteries
that have become narrowed or blocked
(usually as a result of
atherosclerosis).
The procedure involves using addition-
al blood vessels (such as a mammary
artery
or
a vein from
the
leg)
to
improve blood flow to the heart mus-
cle.
A
coronary
artery
bypass
is
performed if symptoms of coronary
artery disease have not been relieved by
drugs, or if balloon
angioplasty
(a sur-
gical procedure used to widen blocked
arteries) is inappropriate or has failed.
Before surgery, sites of blockage are
identified using an imaging procedure
called
angiography.
Usually, a
heart-lung
machine
is needed to maintain the cir-
culation during the operation, although
sometimes
minimally invasive surgery
may
be used to bypass the artery, thereby
avoiding the need to stop the heart.
The
long-term
outlook
is
good
following
a
coronary artery
bypass.
However, the grafted vessels may also
eventually become blocked by athero-
sclerosis. (See also
Coronary artery bypass
box, overleaf.)
coronary artery disease
Narrowing of the
coronary arteries,
w hich supply blood to the heart, lead-
ing to damage or malfunction of the
heart. The most common heart disor-
ders due to coronary artery disease are
angina pectoris
(chest pain due to insuf-
ficient oxygen reaching the heart) and
myocardial infarction
(heart attack).
CAUSES
The usual cause is
atherosclerosis
,
in
w hich fatty plaques develop on artery
linings. An affected vessel can become
totally blocked if a blood clot forms or
lodges in the narrowed area.
Atherosclerosis has many interrelated
causes, including smoking, a high-fat
diet, lack of exercise, being overweight,
and
raised
blood
cholesterol
levels.
Other risk factors include a genetic
predisposition and diseases such as
dia-
betes mellitus
and
hypertension
.
SYMPTOMS
In its early stages, coronary artery dis-
ease often produces no symptoms. The
first sign is frequently the chest pain of
angina, or an actual heart attack.
The disease may also cause arrhyth-
mias (abnormalities in the heartbeat);
in severe cases, arrhythmia can cause
cardiac arrest
(in w hich the heart stops
beating). In elderly people, it may lead
to
heart failure
,
in w hich the heart grad-
ually becomes less and less efficient.
TREATMENT
Drugs are given to help the heart to
function more efficiently and to relieve
symptoms. These include glyceryl tri-
nitrate and other
nitrate drugs
;
calcium
channel blockers
;
beta-blockers
;
potassium
channel activators
;
and
vasodilator drugs
.
If drug treatment fails to relieve the
symptoms of coronary artery disease,
or if there is extensive narrowing of
the coronary arteries, blood flow may
be improved by balloon
angioplasty
or
coronary artery bypass
surgery.
coronary care unit
A specialist ward for the care of acutely
ill patients w ho may have suffered a
myocardial infarction
(heart attack)
or
another serious cardiovascular disorder.
coronary heart disease
An alternative name for
coronary artery
disease
.
coronary thrombosis
A condition
in
w hich
a
thrombus
(blood clot)
narrows or blocks one
of the
coronary arteries
,
thereby prevent-
ing sufficient oxygen from reaching a
section of the heart muscle. In most
cases, the thrombus forms in a blood
vessel that has already been narrowed
by
atherosclerosis
.
Sudden blockage of a
coronary artery w ill cause a
myocardial
infarction
(heart attack).
coroner
A public officer appointed to inquire into
a cause of death when it is unknown or
when unnatural causes are suspected.
cor pulmonale
Enlargement of, and strain upon, the
right side of the
heart
,
that is caused
by one of several chronic lung diseases.
Damage to the lungs leads to
pulmonary
hypertension
(abnormally high blood
pressure in the arteries that supply the
lungs).The resulting “back pressure” of
blood puts strain on the heart, and may
eventually cause right-sided
heart failure
w ith
oedema
.
corpus callosum
The band of nerve fibres that forms a
connection
between the
two
hem i-
spheres of the
brain
.
corpus cavernosum
One of two cylindrical bodies of erec-
tile tissue that is found in both the
clitoris
and the
penis
.
The spongy struc-
ture of the corpus cavernosum allows
the tissue to become rigid when it
becomes filled with blood.
corpuscle
Any minute body or cell, particularly
red and white blood cells or certain
types of
nerve
ending.
corpus luteum
A small tissue mass in the
ovary
that
develops from a ruptured egg
follicle
after
ovulation
(the release of an egg).
The corpus luteum secretes the female
sex hormone
progesterone
,
w hich caus-
es the lining of the uterus to thicken in
preparation for implantation of a fertil-
ized egg. If fertilization does not occur,
the corpus luteum shrinks and dies.
corrosive oesophagitis
A type of
oesophagitis
that is caused by
swallowing caustic chemicals.
corset
A device that is w orn around the trunk
to relieve
back pain
and treat spinal
injuries or deformities.
C
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