Bma Illustrated Medical Dictionary

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 thrombusor 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 treatmentsthat,

in some cases, eliminate the need for

surgery (see angioplasty,balloon; embol-

ization). (See also aortography.)

angiomaA noncancerous tumour made

up of blood vessels (see haemangioma)

or lymph vessels (see lymphangioma).

angioplasty, balloonA 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.Balloonangioplasty is used to

restore blood flow in peripheral vascular

diseaseand coronary artery disease.

Coronary balloon angioplasty is usually

successful, but the narrowing may recur

ANGIOMA ANHEDONIA

A

Inflated balloon

Compressed

fatty deposit

Catheter

Deflated

balloon

Narrowed

area

BALLOON IN POSITION BALLOON INFLATED

Artery wall

ANGIOPLASTY, BALLOON

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.

angiotensinThe 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 narrowingof 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 hypertension. Whatever the cause of

hypertension, it may be treated with

drugs called ACE inhibitors, which work

by reducing angiotensin II formation.

angiotensin converting enzymeA

substance that converts angiotensin I to

its active form, angiotensin II. Drugs

that reduce the action of this enzyme

are known as ACE inhibitor drugsand

are used in the treatment of hyperten-

sion and heart failure.

angiotensin II antagonistsA group

of drugs used in the treatment of hyper-

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