Encyclopedia of Health and Medicine

cardiomyopathy 31
that would challenge even someone in peak cardiovascular
function. Neither extreme is healthy
and can result in further health problems. A person
who has not been physically active for years
to decades often benefits from the advice and suggestions
of a health expert who can help determine
an appropriate entry point for returning to
an active lifestyle.
Recent studies affirm that cardiac rehabilitation
has therapeutic value for people who have
chronic cardiovascular conditions such as congestive
HEART FAILURE, improving symptoms and QUAL-
ITY OF LIFE. Many people will begin cardiac
rehabilitation before leaving the hospital after
treatment or surgery, starting with an exercise
STRESS TEST to determine cardiopulmonary capacity,
and continue in a structured way for 3 to 6
months. Under ideal circumstances the activities
of rehabilitation, including EATING HABITS and
nutrition, become elements of routine daily living
and foster a lifestyle that supports cardiovascular
health.
See also DIET AND HEALTH; EXERCISE AND HEALTH;
LIFESTYLE AND CARDIOVASCULAR HEALTH; NUTRITIONAL
ASSESSMENT; NUTRITIONAL NEEDS; PHYSICAL EXERCISE
AND CARDIOVASCULAR HEALTH; SEXUAL ACTIVITY AND
CARDIOVASCULAR DISEASE.
cardiac resynchronization therapy (CRT) A
method of biventricular pacing in which an
implanted device regulates and coordinates the
contractions of both ventricles, typically to treat
severe HEART FAILURE. SUDDEN CARDIAC DEATH as a
result of ARRHYTHMIA is a significant risk in HEART
failure, particularly heart failure resulting from
dilated CARDIOMYOPATHY. Certain BUNDLE BRANCH
BLOCK arrhythmias also benefit from CRT.
Conventional pacing therapy stimulates only
the right ventricle, which in an otherwise healthy
heart results in contraction of both ventricles as
the electrical impulse spreads simultaneously
across them. In severe heart failure, however,
both ventricles are extensively damaged and do
not function in synchronization. Conventional
pacing therapy ends up being counterproductive
by further extending the dysfunction between the
two ventricles. A biventricular PACEMAKER has two
leads (wires that conduct electrical impulses), one
of which the cardiologist inserts in each ventricle.
The pacemaker’s discharge sends impulses simultaneously
to each lead.
The risks of CRT are similar to those of conventional
pacing therapy and include possible INFEC-
TION or blood clots from the inserted leads. These
risks are minimal, however, and CRT provides
substantial benefit for people whose arrhythmias
due to heart failure do not respond to other treatments.
See also IMPLANTABLE CARDIOVERTER DEFIBRILLATOR.
cardiomyopathy Weakness and loss of pumping
effectiveness of the HEART, usually with changes to
the structure of the heart and in particular the left
ventricle. Cardiomyopathy is as likely to affect
people under age 40 as people over age 60 and is a
leading cause of HEART FAILURE resulting in HEART
TRANSPLANTATION. Genetic factors can play a role in
cardiomyopathy, especially in younger people,
though lifestyle factors such as nutrition and ALCO-
HOL consumption are also significant. Viral and
bacterial infections of the heart (MYOCARDITITIS) can
leave the heart MUSCLE damaged. In many situations,
however, doctors do not know what causes
the structural and functional changes in myocardial
(heart muscle) cells that result in primary cardiomyopathy.
Secondary cardiomyopathy may
also develop as a consequence of other CARDIOVAS-
CULAR DISEASE (CVD), such as ISCHEMIC HEART DISEASE
(IHD) and HYPERTENSION (high BLOOD PRESSURE).
The five major types of cardiomyopathy are
• Dilated cardiomyopathy, in which the heart
enlarges in an attempt to compensate for damage
to myocardial cells that limits the heart’s
ability to efficiently pump BLOOD. Long-term
ALCOHOL abuse accounts for the dilated cardiomyopathy
in about a third of the people
who develop it. Deficiency of vitamin B 1 also
damages the heart. Though uncommon in the
general US population, vitamin B 1 deficiency
can occur with long-term, heavy alcohol consumption
as well as with long-term EATING
DISORDERS such as anorexia nervosa. Dilated
cardiomyopathy is more common in people
over age 60.
• Hypertrophic cardiomyopathy, in which
the walls of the heart, particularly the ventricles,
thicken. Some doctors may refer to this