can cause fainting, dizziness, chest
pain, and breathlessness, which may be
the 1st symptoms.
Arrhythmias are diagnosed by an ECG.
If they are intermittent, a continuous
recording may need to be made using
an ambulatory ECG.
Treatments for arrhythmias include anti-
arrhythmic drugs, 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
defibrillation). Abnormal conduction path-
ways in the heart can be treated using
radio frequency ablation during cardiac
catheterization (see catheterization, car-
diac). In some cases, a pacemaker can
be fitted to restore normal heartbeat by
overriding the heart’s abnormal rhythm.
arsenicA poisonous metallic element
that occurs naturally in its pure form
and in various compounds. Arsenic poi-
soning, which is now rare, used to occur
as a result of continuous exposure to
industrial pesticides.
arterial reconstructive surgeryAn
operation to repair arteriesthat are nar-
rowed, blocked, or weakened. Arterial
reconstructive surgery is most often
performed to repair arteries that have
been narrowed by atherosclerosis. It is
also used to repair aneurysms and
arteries damaged as a result of injury.
(See also angioplasty,balloon; coronary
artery bypass; endarterectomy.)
arteries, disorders ofDisorders of
the arteries may take the form of abnor-
mal narrowing (which reduces blood
flow and may cause tissue damage),
complete obstruction (which may cause
tissue death), or abnormal widening
and thinning of an artery wall (which
may cause rupture of the blood vessel).
Atherosclerosis, in which fat deposits
build up on artery walls, is the most
common arterial disease. It can involve
arteries throughout the body, including
the brain (see cerebrovascular disease),
heart (see coronary artery disease), and
legs (see peripheral vascular disease).
Atherosclerosis is the main type of art-
eriosclerosis, a group of disorders that
cause thickening and loss of elasticity
of artery walls. Hypertension is anothercommon cause of thickening and nar-
rowing of arteries, and it increases the
risk of a strokeor kidney failure. Arteritis
is inflammation of artery walls that
causes narrowing and sometimes block-
age. Aneurysmis ballooning of an
artery wall caused by the pressure of
blood flowing through a weakened area.
Thrombosisoccurs when a blood clot
forms in a blood vessel, causing obs-
truction of the blood flow. Blockage of
an artery by a fragment of blood clot or
other material travelling in the circula-
tion is called an embolism. Raynaud’s
diseaseis a disorder involving intermit-
tent spasm of small arteries in the
hands and feet, usually due to cold.
arteriographyAn alternative name for
angiography, an X-ray technique for
imaging arteries.
arterioleA blood vessel that branches
off an artery. Arterioles branch to form
capillaries. They have muscular walls,
and their nerve supply enables them to
be narrowed or widened to meet the
blood-flow needs of tissues they supply.
arteriopathyAny disorder of an artery
(see arteries,disorders of).
arterioplastySurgical repair of an art-
ery (see arterial reconstructive surgery).
arteriosclerosisA group of disorders
that cause thickening and loss of elas-
ticity of artery walls. Atherosclerosisis
the most common type , and the 2 terms
are often used synonymously. Other
types are medial arteriosclerosis (in
which muscle and elastic fibres in larger
arteries are replaced by fibrous tissue)
and Monckeberg’s arteriosclerosis (in
which there are calcium deposits in the
arterial lining).
arteriovenous fistula An abnormal
communication directly between an art-
ery and a vein. An arteriovenous fistula
may be present at birth or result from
injury. A fistula can also be created
surgically for easy access to the blood-
stream in dialysis.
arteritisInflammation of an artery wall,
causing narrowing or complete block-
age of the affected artery, reduced
blood flow, and, in some cases, throm-
bosis and tissue damage. There are
several types, including Buerger’s dis-
ease, an arteritis that affects the limbs,ARSENIC ARTERITISA