heart muscle is either partially or com-
irregular heartbeat. Periods of bradycar-
tachycardia due to a fault in impulse
sick sinus syndrome).
of arrhythmia is
coronary artery disease,
in which the
(fat deposits on the artery
(heart attack). Some
tachycardias are the result of a
heart's conducting system.
can cause seri-
ous cardiac arrhythmias if they are taken
in high doses.
An arrhythmia may be felt as pal-
becomes aware of an abnormally rapid
ziness as a result of reduced blood
flow to the brain, or chest pain and
breathlessness if there is a reduction in
blood flow to the lungs. These may be
the first symptoms.
Arrhythmias are diagnosed by an
which shows the pattern of electrical
activity within heart muscle.
arrhythmia is intermittent, a continuous
recording may need to be made using
Treatments for arrhythmias include
which prevent or slow
tachycardias. With an arrhythmia that
has developed suddenly, it may be pos-
sible to restore normal heart rhythm by
using electric shock to the heart (see
Repeated attacks of tachycardia can
sometimes be treated by radio frequency
ablation (the removal of dead or diseased
tissue) of the heart’s abnormal conduc-
tion pathway This may be carried out
In some cases, a
pacemaker can be fitted to restore nor-
mal heartbeat by overriding the heart’s
A starchy substance that is obtained
from the roots of the West Indian plant
MAEANTA ARUNDINACEA. Arrowroot was
traditionally used an an easily digestible
mixed to a paste with milk or water or
used as an ingredient in biscuits.
occurs naturally in its pure form and
various compounds. Arsenic poisoning,
which is now rare, once occurred as a
result of continuous industrial or pesti-
arterial reconstructive surgery
An operation to repair
narrowed, blocked, or weakened.
WHY IT IS DONE
Arterial reconstructive surgery is most
often performed to repair arteries that
have been narrowed by
(fatty deposits on artery walls). It is also
used to repair
and arteries damaged as a
result of injury.
HOW IT IS DONE
A narrowed or blocked section of artery,
particularly a coronary artery, can be
bypassed by sewing in a length of vein
above and below the constricted area.
Elsewhere in the body, the affected sec-
tion is commonly replaced using an
artificial tube or a section of vein. (See
arteries, disorders of
Disorders of the arteries may take the
form of abnormal narrowing (which
reduces blood flow and may cause tis-
(which may cause tissue death), or
abnormal widening and thinning of an
artery wall (which may cause rupture
of the blood vessel).
in which fat deposits
build up on the lining of artery walls, is
the most common arterial disease. It
body, including the brain
and legs (see
). Atherosclerosis is the
main type of
a group of
disorders that cause thickening and loss
of elasticity of artery walls.
(high blood pressure) is
another common cause of thickening
and narrowing of arteries. Hyperten-
sion predisposes people to coronary
artery disease and increases the risk of a
is inflammation of artery walls
that causes narrowing and sometimes
is ballooning of an artery
wall caused by the pressure of blood
flowing through a weakened area.
occurs when a thrombus
(blood clot) forms in a blood vessel,
causing obstruction of the blood flow.
is blockage of an artery
by a fragment of blood clot or other
material travelling in the circulation.
is a disorder in
which there is intermittent spasm of
small arteries in the hands and feet,
usually precipitated by the cold.
An alternative name for
X-ray technique for imaging arteries.
A blood vessel that is a branch from an
and which branches further to
Arterioles have mus-
and their nerve supply
widened to meet the blood-flow needs
of tissues they supply.
Any disorder of an artery (see
Surgical repair of an artery (see
A group of disorders that cause thicken-
ing and loss of elasticity of artery walls.
is the most common type
of arteriosclerosis, and the two terms are
often used synonymously.
Other types are medial arteriosclero-
sis (in which muscle and elastic fibres
in larger arteries are replaced by fibrous
tissue) and Monckeberg’s arteriosclero-
sis (in which there are calcium deposits
in the arterial lining).
An abnormal communication directly
between an artery and a vein. An arteri-
ovenous fistula may be present at birth
or may result from injury. A fistula can
also be created surgically for easy access
to the bloodstream, as occurs in
If the fistula is close to the skin sur-
face it may cause a small, pulsating
swelling. If several are present in the
lungs, uptake of oxygen into the blood