- IMPLANTABLE CARDIOVERTER DEFIBRILLATOR (ICD),
which functions both to deliver pacing impulses
and shocking impulses to convert an arrhyth-
mia that extends beyond certain parameters
Most people are able to successfully control or
eliminate arrhythmias with appropriate treatment,
resulting in no changes to lifestyle or quality of life.
Risk Factors and Preventive Measures
Most arrhythmias arise as a consequence of other
CARDIOVASCULAR DISEASE (CVD) or are idiopathic
(without identifiable cause). Some arrhythmia dis-
orders are congenital or genetic, such as LONG QT
SYNDROME(LQTS). People who have one kind of
arrhythmia are prone to developing others.
Prompt medical evaluation of symptoms that
could signal cardiovascular disease or arrhythmias
is important, as early detection and treatment may
head off consequences such as CARDIAC ARRESTor
SUDDEN CARDIAC DEATH.
See also AUTOMATED EXTERNAL DEFIBRILLATOR
(AED); BUNDLE BRANCH BLOCK; CARDIOPULMONARY
RESUSCITATION (CPR); GENERIC DRUG; PAROXYSMAL
ATRIAL TACHYCARDIA (PAT); PREMATURE VENTRICULAR
CONTRACTION; STRESS AND STRESS MANAGEMENT;
STROKE; TORSADE DE POINTES; WOLFF-PARKINSON-
WHITE SYNDROME.
arteriosclerosis A degenerative condition of the
arteries in which the walls of the arteries become
stiff and rigid. Arteriosclerosis is a leading factor in
age-related HYPERTENSION (high BLOOD PRESSURE).
There are three forms of arteriosclerosis:
- ATHEROSCLEROSIS in which arterial plaque
deposits infiltrate the inner layer of the arterial
wall - Mönckeberg’s arteriosclerosis or medial calcific
sclerosis, in which the medial layer of the arte-
rial wall accumulates calcium deposits that
cause the ARTERYto become rigid - arteriolosclerosis in which the arterioles (the
threadlike arteries that form the arterial portion
of the CAPILLARY BEDS) lose their FLEXIBILITYand
elasticity
The primary causes of arteriosclerosis include
cigarette smoking (NICOTINEis highly toxic to the
smooth MUSCLEfibers of the arteries),DIABETES, and
hypertension. The consequences of arteriosclero-
sis, particularly atherosclerotic, include increased
risk for HEART ATTACK, STROKE, ANEURYSM, and
increased hypertension. People often use the
terms atherosclerosis and arteriosclerosis inter-
changeably, which is not quite accurate though is
correct about 90 percent of the time because ath-
erosclerosis is the most common form of arte-
riosclerosis.
See also DIABETES AND CARDIOVASCULAR DISEASE;
HYPERLIPIDEMIA; LIFESTYLE AND CARDIOVASCULAR
HEALTH.arteriovenous malformation (AVM) A congeni-
tal deformity in which an entanglement of arteries
and veins forms. Rather than connecting into CAP-
ILLARY BEDSthat form between them, the arteries
and veins in an AVM connect directly to one
another. Veins lack the structure to accommodate
the pressure BLOODis under as it flows through the
arteries and over time may become weakened and
rupture. The resulting bleeding can be life-threat-
ening, depending on the size and location of the
AVM. Most AVMs are in the BRAIN, although an
AVM can occur in other parts of the body. Though
AVMs are present at birth, many do not show
symptoms until later in life, even adulthood.
The symptoms of AVM vary and often are
vague, making diagnosis sometimes difficult. Cere-
bral AVMs (AVMs in the brain) may cause
HEADACHE, seizures, and STROKE-like symptoms if
they apply pressure to surrounding brain tissue or
if they bleed. HEMORRHAGEin the brain can cause
permanent damage to the brain, resulting in
PARALYSIS, cognitive loss, or death. AVMs elsewhere
in the body may cause PAINor bleeding; hemor-
rhagic bleeding is life-threatening. COMPUTED
TOMOGRAPHY (CT) SCAN and magnetic resonance
angiography, which combines MAGNETIC RESONANCE
IMAGING(MRI) with dye injected into the blood ves-
sels, are the key diagnostic procedures to detect
AVM.
Treatment depends on the size and location of
the AVM and may include surgery to remove the
web of blood vessels, injection of a substance to
block the flow of blood through the AVM
(embolization), or RADIOFREQUENCY ABLATIONto close
off the blood vessels. Treatment often carries signif-arteriovenous malformation (AVM) 19