Bma Illustrated Medical Dictionary

pacemakerA small device that supplies

electrical impulses to the heartto main-

tain a regular heartbeat. A pacemaker is

implanted when the sinoatrial nodein

the heart malfunctions, or when the pas-

sage of the electrical impulses that

stimulate heart contractions is impaired

(see heart block; sick sinus syndrome).

Pacemakers can be fixed-rate (which

discharge impulses at a steady rate) or

demand (which discharge only when the

heart rate slows or a beat is missed).

They may be external (used as a tempo-

rary measure) or internal (implanted in

the chest). Some types can increase the

heart rate during exercise or change an

abnormal rhythm into a normal one.

paclitaxelAn anticancer drugthat is

used to treat certain types of cancer,

such as ovarian cancer (see ovary, cancer

of) andbreast cancer. The possible side

effects of paclitaxel can include nausea,

vomiting, anaemia, and increased sus-

ceptibility to infection.

paediatricsThe branch of medicine that

is concerned with the development of

children, and the diagnosis, treatment,

and prevention of childhood diseases.

paedophiliaSexual attraction to chil-

dren. (See also child abuse; incest.)

Paget’s diseaseA common disorder of

the middle-aged and elderly, in which the

formation of bone is disrupted. Affected

bones become weak, thick, and deform-

ed. Paget’s disease, which is also called

osteitis deformans, usually affects the

pelvis, skull, collarbone, vertebrae, and

long bones of the leg. The disorder may

run in families and mostly affects men.

There are often no symptoms, but if

symptoms do occur, the most common

ones are bone pain and deformity, espe-

cially bowing of the legs. Affected bones

are prone to fracture. Skull changes may

lead to leontiasis (distortion of the facial

bones producing a lion-like appearance)

and to damage to the inner ear, some-

times causing deafness, tinnitus, vertigo,

or headaches.

The disorder is diagnosed by X-rays

and blood tests. Most people do not need

treatment, or only need analgesic drugs.

In more severe cases, treatment with

drugs such as calcitoninmay be pre-

scribed or surgery may be needed.

Paget’s disease of the nippleA rare

type ofbreast cancerin which a tumour

develops in the nipple. The disease

resembles eczemaand can cause itching

and a burning feeling. A non-healing

sore may develop. Without treatment,

the tumour may spread into the breast.

Diagnosis is made with a biopsy.

painA localized sensation that can range

from mild discomfort to an excruciating

experience. Stimulation of sensory nerve

endings called nociceptors in the skin

leads to pain messages being sent to

the brain. Some nociceptors respond

only to severe stimulation, others to

warning stimuli. Pain receptors are pre-

sent in other structures, such as blood

vessels and tendons. Pain that may be

felt at a point some distance from the

cause is known as referred pain.

Treatment for pain may include drugs,

electrical stimulation (TENS), surgery,

or therapies such as acupuncture. (See

also pain relief, endorphins.)

painful arc syndromeA condition in

which pain occurs when the arm is raised

between 45 and 160 degrees from the

side. The usual cause is an inflamed

PACEMAKER PAINFUL ARC SYNDROME

P

Electrical

wires

Superior

vena

cava

Wire to right

ventricle

PACEMAKER

Pacemaker

Wire to

right

atrium

INTERNAL PACEMAKER IN POSITION

P