An
estimated 4.8 million Americans have congestive heart failure
(CHF). Increasing prevalence, hospitalizations, and deaths have
made CHF a major chronic condition in the United States. It often
is the end stage of cardiac disease. Half of the patients diagnosed
with CHF will be dead within 5 years. Each year, there are an
estimated 400,000 new cases. The annual number of deaths directly
from CHF increased from 10,000 in 1968 to 42,000 in 1993 (figure
1), with another 219,000 related to the condition.
CHF
is the first-listed diagnosis in 875,000 hospitalizations, and
the most common diagnosis in hospital patients age 65 years and
older. In that age group, one fifth of all hospitalizations have
a primary or secondary diagnosis of heart failure.
Visits
to physicians' offices for CHF increased from 1.7 million in 1980
to 2.9 million in 1993. More than 65,000 persons with CHF receive
home care each year. In 1993, an estimated $17.8 billion was spent
for the care of CHF patients in hospitals, physicians' offices,
home care, and nursing homes as well as for medication. The financial
and other losses of caregivers for these patients are large as
well.
The
magnitude of the problem of CHF is large now, but it is expected
to get much worse because:
- As
more and more cardiac patients are able to survive and live
longer with their disease, their opportunity for developing
CHF increases.
- Future
growth in the elderly population will likely result in increasing
numbers of persons with this condition regardless of trends
in coronary disease morbidity and mortality.
Incidence
Incidence
data on congestive heart failure are not available on a national
basis. The following estimates are from the study in Framingham,
Massachusetts, funded by the National Heart, Lung, and Blood Institute.
Incidence of CHF is equally frequent in men and women, and annual
incidence approaches 10 per 1,000 population after 65 years of
age. Incidence is twice as common in persons with hypertension
compared with normotensive persons (figure 2) and five times greater
in persons who have had a heart attack compared to persons who
have not (figure 3).
Prevalence
According
to the National Health and Nutrition Examination Surveys, an estimated
4.8 million Americans have congestive heart failure, with approximately
equal numbers of men and women. Almost 1.4 million are under 60
years of age. CHF is present in 2 percent of persons age 40 to
59, more than 5 percent of persons age 60 to 69, and 10 percent
of persons age 70 and older (figure 4). Prevalence is at least
25 percent greater among the black population than among the white
population. Prevalence at each age increased substantially between
two periods surveyed nationally: 1976-80 and 1988-91 (figure 5).
Hospitalizations
The
rate of hospitalizations for heart failure increased more than
three times between 1970 and 1994 at age 45 to 64 and age 65 and
older, with a large absolute increase in the older age group (figure
6). In 1994, CHF was the first-listed discharge diagnosis in 874,000
hospital discharges (alive or dead) and a secondary diagnosis
in another 1.8 million discharges. One in five of all discharged
patients age 65 and older had CHF as a primary or secondary diagnosis.
The percentage of CHF patients discharged dead from hospitals,
however, decreased from 11.3 percent in 1981 to 6.1 percent in
1993. This trend is seen for persons age 45 to 64 and for those
age 65 and older (figure 7).
Prognosis
Survival
following diagnosis of congestive heart failure is worse in men
than women, but even in women, only about 20 percent survive much
longer than 8 to 12 years. The outlook is not much better than
for most forms of cancer. The fatality rate for CHF is high, with
one in five persons dying within 1 year. Sudden death is common
in these patients, occurring at a rate of six to nine times that
of the general population. Thus, CHF remains a highly lethal condition.
With the use of angiotensin-converting enzyme (ACE) inhibitors
as a possible exception, advances in the treatment of hypertension,
myocardial ischemia, and valvular heart disease have not resulted
in substantial improvements in survival once CHF ensues.
Mortality
The
death rate for congestive heart failure increased most years between
1968 and 1993 (figure 1). These increases are in contrast to mortality
declines for most heart and blood vessel diseases. In 1993, there
were 42,000 deaths where CHF was identified as the primary cause
of death and another 219,000 deaths where it was listed as a secondary
cause on the death certificate. The death rate for CHF in 1993
was nearly 1.5 times higher in black men and women than in white
men and women (figure 8).
Research
The
National Heart, Lung, and Blood Institute (NHLBI) supports a wide
range of basic, clinical, and epidemiological research to better
understand the causes and improve the prevention, diagnosis, and
treatment of CHF. The studies include investigations of how the
heart contracts normally and what goes wrong in CHF, the development
of new drug therapies and other innovative treatments of CHF,
and ways to better detect the condition in those at a high risk
of CHF.
Some
studies are trying to stop the loss of cell function that happens
in CHF. Muscle cells die or no longer function properly, which
causes the heart to lose its ability to pump blood. In studies
on animals, researchers have begun inserting healthy muscle cells
into a failing heart to replace damaged cells. Results so far
have been promising: The grafted cells appear to thrive and function
normally. This animal research has shown that the grafted cells
can even come from muscles other than the heart, such as muscles
of the leg. Furthermore, it may be possible to genetically engineer
grafted cells to make them stronger.
Other
studies are developing drugs with multiple actions to treat CHF.
Such a drug would have several effects. For example, a drug might
improve the heart's pumping ability, open clogged arteries, and
prevent tissue damage from free radicals, a byproduct of the body's
metabolic processes. Free radicals are thought to contribute to
the development of atherosclerosis. One of these multiple-acting
drugs has already been tested and appears not only to lengthen
survival but also to improve symptoms for those with CHF.
Investigations
also are being done to improve heart transplantation for CHF patients.
In some cases, a heart transplant is the only possible treatment.
However, such patients face a shortage of donor hearts. A possible
solution to this critical shortage may be the use of a heart from
other animals. Called xenotransplantation, this procedure once
was made difficult because of the rejection of the heart by the
CHF patient's immune system. However, new technologies have been
forged that can overcome such a barrier. For example, scientists
have been able to alter genes in the heart of a pig to diminish
the immune system reaction in a baboon. Scientists still need
to discover how to turn such genes on and off to prevent human
rejection.
Researchers
are continuing efforts to develop better devices to help the damaged
heart function. Already in use is a small mechanical pump called
a left ventricular assist device (LVAD). The ventricles are the
heart's main pumping chambers. These chambers enlarge as CHF progresses.
Muscle fibers stretch, and the heart loses strength. The LVAD
is now used as a temporary assist for patients with severe CHF
who are awaiting a heart transplant. However, researchers have
found that the heart in patients with an LVAD often improves after
months of use--so much that a transplant is no longer needed.
Thus, efforts are underway to identify patients who may benefit
from a longer-term LVAD.
Through
its national education efforts, the NHLBI is working to prevent
CHF too, especially through the early detection and aggressive
treatment of high blood pressure and heart attack--the two leading
causes of CHF. New drug therapies, better diagnosis, and speedier
therapies are lessening those conditions' impact on the heart.
Source:
The National Heart, Lung, and Blood Institute & the National
Institutes of Health
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