ANGIOMA
ANHEDONIA
that is opaque to X-rays). Angiography
is used to detect conditions that alter
the appearance of blood vessels, such
as
aneurysm,
and narrowing or blockage
of blood vessels by
atherosclerosis,
or by
a
thrombus
or
embolus.
It is also used to
detect changes in the pattern of blood
vessels that supply organs injured or
affected by a tumour.
Carotid angiography (of the arteries in
the neck) may be used to investigate
transient ischaemic attacks.
Cerebral ang-
iography can be used to detect an
aneurysm in the brain or pinpoint the
position of a brain tumour. Coronary
angiography, often combined with car-
diac
catheterization,
can identify the
sites of narrowing or blockage in
coron-
ary artery disease.
Digital subtraction
angiography uses computer techniques
to process images and remove unwant-
ed background information.
Angiographic techniques have been
adapted to allow certain treatments that,
in some cases, eliminate the need for
surgery (see
angioplasty, balloon; em bol-
ization).
(See also
aortography.)
angioma A noncancerous tumour made
up of blood vessels (see
haemangioma)
or lymph vessels (see
Ij/mphangioma).
angioplasty, balloon A technique for
treating a narrowed or blocked section
of blood vessel by introducing a catheter
with a balloon into the constricted area.
The balloon is inflated to widen the nar-
rowed area, deflated again, and then
removed. Balloon angioplasty is used to
restore blood flow in
peripheral vascular
disease
and
coronary artery disease.
Coronary balloon angioplasty is usually
successful, but the narrowing may recur
in the affected vessel, requiring repeat
treatment. Angioplasty of peripheral ves-
sels is most successful in treating the
iliac and femoral arteries in the legs,
angiotensin The name of 2 related pro-
teins
involved
in
regulating
blood
pressure. The 1st, angiotensin I, is inac-
tive and is formed when renin, which is
produced by the kidneys, acts on the
substance angiotensinogen. Angioten-
sin I is then converted to the second,
active, form, angiotensin II, by angio-
tensin-converting enzyme. Angiotensin II
causes narrowing of the small blood
vessels in tissues, resulting in increased
blood pressure. It also stimulates re-
lease (from the adrenal cortex, the outer
part of each
adrenal gland)
of the hor-
mone
aldosterone,
which also increases
blood pressure.
Certain kidney disorders can increase
the production of angiotensin II, caus-
ing hj
rpertension.
Whatever the cause of
hypertension, it may be treated with
drugs called
ACE inhibitors,
which work
by reducing angiotensin II formation,
angiotensin converting enzyme A
substance that converts angiotensin I to
its active form, angiotensin II. Drugs
that reduce the action of this enzyme
are known as
ACE inhibitor drugs
and
are used in the treatment of hyperten-
sion and heart failure,
angiotensin II antagonists A group
of drugs used in the treatment of hj/per-
tension
(high blood pressure). They
have a similar action to
ACE inhibitors
but do not cause a dry cough. Examples
are losartan and valsartan.
anhedonia Total loss of the feeling
of pleasure from activities that would
ANGIOPLASTY, BALLOON
Compressed
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