ATRIAL FLUTTER
A
heartbeat),
angina pectoris
(chest pain as
due to impaired blood supply to the
heart muscle), or breathlessness. The
inefficient pumping action of the heart
reduces the output of blood into the
circulation. Blood clots may form in
the atria and may enter the bloodstream
and lodge in an artery (see
embolism).
DIAGNOSIS AND TREATMENT
Diagnosis of atrial fibrillation is con-
firmed by an
ECG,
which shows the
electrical activity of the heart.
Digoxin
or
beta-blocker drugs
may be
given to control the heart rate. If the
atrial fibrillation is of recent onset, it
may be reversed by
defibrillation
(the
application of a short electric shock to
the heart). In most cases,
anticoagulant
drugs
or
aspirin
are also given to reduce
the risk of an embolism occurring.
atrial flutter
A type of abnormality of the heartbeat
(see
arrhythmia
,
cardiac
) in which the
atria
(see
atrium),
the heart’s upper
chambers beat regularly but very rapidly.
Symptoms and treatment of atrial flutter
are the same as for
atrial fibrillation
.
atrial natriuretic peptide
A substance that is produced in special
cells in the muscular wall of the atria
(see
atrium),
the upper chambers of the
heart. Atrial natriuretic peptide is rel-
eased into the bloodstream in response
to swelling of the atrial muscle due, for
example, to
heart failure
or
hypertension
(high blood pressure).
Atrial natriuretic peptide increases
the amount of sodium excreted in the
urine. Sodium draws water out with it,
which decreases the volume of the
blood, thereby reducing blood pressure.
Children who have congenital (pre-
sent from birth) heart disorders that
result in heart disease (see
heart disease,
congenital
) possess high levels of atrial
natriuretic
peptide.
Following
suc-
cessful surgery to correct the heart
abnormality, the levels of atrial natri-
uretic peptide fall.
atrial septal defect (ASD)
A congenital (present from birth) heart
abnormality
(see
heart disease, con-
genital
) in which there is a hole in the
dividing wall (see
septal defect
) between
the heart’s two upper chambers, or atria
(see
atrium
).
atrioventricular block
A type of
heart block.
atrioventricular node
A small knot of specialized muscle cells
in the right
atrium
(upper chamber) of
the
heart.
Electrical impulses from the
sinoatrial node
(a cluster of muscle cells
that act as the heart’s natural pacemaker)
pass through the atrioventricular node
and along conducting fibres to the
ven-
tricles
(the
lower
chambers
of the
heart), causing them to contract and
pump blood around the body.
atrium
Also known as an auricle, either of
the two (right and left) upper chambers
of the
heart.
The atria open directly
into the
ventricles
(the lower chambers
of the heart). Deoxygenated blood from
the
body
enters
the
right
atrium
through the
venae cavae.
Oxygenated
blood from the lungs enters the left
atrium through the
pulmonary veins.
atrophy
The wasting away or shrinkage of a nor-
mally developed tissue or organ that
results from a reduction in the size or
number of its cells.
Atrophy is commonly caused by dis-
use (such as when a limb has been
immobilized in a plaster cast) or inade-
quate cell nutrition as a result of poor
blood circulation. Atrophy may also
occur during prolonged illness, when
the body needs to use up the protein
reserves in the muscles. In some cir-
cumstances, atrophy is a normal process
(as in ovarian atrophy, for example,
which occurs in women who have
passed the
menopause
.
atropine
An
anticholinergic drug
that is derived
from the deadly-nightshade plant (see
belladonna
). Atropine is used to dilate
the pupil in eye conditions such as
iritis
(inflammation of the iris) and
corneal
ulcer.
It is also used in young children,
in the form of eye-drops, to dilate
(widen) the
pupil
for examination.
Atropine was often given (by injec-
tion) as a
premedication
before a general
anaesthetic (see
anaesthesia, general)
to
reduce secretions from the lungs, but it
is now rarely used for this purpose. It is
used as emergency treatment for
brady-
cardia
(abnormally slow heartbeat) and is
also sometimes prescribed for its anti-
cholinergic effects; it is combined with
an
antidiarrhoeal drug
to relieve the abdo-
minal cramps that accompany diarrhoea.
Side effects include dry mouth, blur-
red vision, retention of urine, and, in the
elderly, confusion. Atropine eye-drops
are rarely given to adults because they
cause disturbance of vision that lasts for
two to three weeks and may precipitate
acute
glaucoma
in susceptible people.
attachment
An affectionate bond between individu-
als, especially between a parent and
child (see
bonding)
or between a person
and an object, such as a young child
and a security blanket.
The term attachment is also used to
refer to the site at which a muscle or
tendon is attached to a bone.
attempted suicide
See
suicide, attempted.
attention deficit hyperactivity
disorder (ADHD)
A behavioural disorder in which a child
has a consistently high level of activity
and/or difficulty in attending to tasks.
Attention
deficit
hyperactivity,
or
hyperkinetic, disorder affects up to five
per cent of children in the UK.
The disorder, which is more com-
mon in boys, should not be confused
with the normal boisterous conduct of
a healthy child. Children with ADHD
show abnormal patterns of behaviour
over a period of time. An affected child
is likely to be constantly restless, unable
to
sit
still
for
more
than
a
few
moments, inattentive, and impulsive.
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