Unstable angina
Alternative names:
accelerating angina; angina - unstable; new-onset angina;
progressive angina
Definition:
A pain or discomfort in
the chest or adjacent areas caused by inadequate blood
flow to the heart; distinguished from stable
angina, acute MI
(heart attack), and non-cardiac
chest pain by the pattern,
severity, and frequency of symptoms and the level of activity
that precipitates the discomfort.
Causes, incidence, and risk factors:
Unstable angina occurs in approximately 6 out of 10,000
people. Coronary artery disease
is by far the most common cause of unstable angina. A coronary
artery spasm may cause angina
in less than 10% of cases.
Initally, narrowing (plaques) of the coronary arteries occurs
and may be severe enough to cause stable
angina with exertion or stress.
This narrowing, however, may not cause any symptoms at all.
For reasons not well understood, the plaques reach a point
at which they rupture. Under these circumstances, a plug formed
by platelets and blood
clots may form causing an already narrowed blood vessel
to become "high-grade." This inherently unstable situation
may progress to complete occlusion and infarction (cell death)
or the lesion may heal. When this plug completely occludes
a coronary artery, a heart attack occurs.
Once this type of lesion exists, onset of chest pain is "unstable."
Unlike stable angina, in which chest pain can be induced by
exercise or stress, chest
pain secondary to unstable angina may occur at rest and
without any precipitating factors at all. Pain may increase
in the severity, frequency, or duration at low levels of activity
or for no identifiable reason. Diabetes
mellitus, hypertension,
myxedema, peripheral
vascular disease, heart valve disease, cardiomyopathy
, and atherosclerosis
may also produce angina.
Risk factors for unstable angina are similar to those for
stable angina, and include:
Occasionally, sudden overwhelming stress can precipitate
an episode of angina.
Update Date: 06/22/00
Updated by: David H. Stern, MD Chief Medical
Resident, University of Pennsylvania Hospital, VeriMed Healthcare
Network
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