Most people recognise that heart attacks are a common
cause of death, particularly in the Western World. What
is less well known is that in many people with heart
disease, the heart fails less dramatically. The 'pump'
function of the heart progressively deteriorates, often
gradually over a period of several years, leading
ultimately to 'pump' failure and, consequently, death –
this sequence of deterioration is called heart
failure.
The combined figure for North America,
Western Europe and Japan for people affected by chronic
heart failure exceeds 10 million. In Europe, there are
over 5 million patients with heart failure. The number
of patients developing heart failure per annum in the UK
is approximately 2.3 per 1000 members of the population
and over 400,000 new cases of heart failure occur every
year in the USA. Heart failure is extremely common and
it is increasing world-wide.
What is Heart Failure? Heart failure is not
a single disease but represents the endpoint of a number
of disease processes. The heart is normally a strong
muscular pump, able to drive blood throughout the body
to maintain the supply of oxygen. In heart failure, the
pump function of the heart gradually deteriorates, so
that it is no longer able to meet the body's metabolic
requirements.
Congestive heart failure interferes
with the kidney's normal function of eliminating excess
sodium and waste from the body. The excess fluid
retained causes swelling of the ankles and legs. Fluid
may also collect in the lungs – resulting in shortness
of breath. The severity of the condition and symptoms
depends on how much of the heart's pumping capacity has
been lost.
The body can compensate for the
deterioration in cardiac function for some time, but in
the long term it has a negative effect. At first, the
deterioration may only be noticeable by a shortness of
breath and fatigue when the individual puts stress on
their heart during exercise. Over time cardiac function
deteriorates to the point where the heart is no longer
able to meet the body's metabolic demands, even when the
sufferer is at rest.
During the course of their
disease, unless treated appropriately, people with heart
failure suffer a substantial loss of quality of life and
frequently have to be admitted to hospital.
Management of Heart Failure The goal of
treatment is to improve a person's quality of life by
making the appropriate lifestyle changes and
implementing drug therapy. Effective treatments exist to
manage and improve heart failure, including diuretics
and ACE inhibitors. Most recently drugs called beta
blockers have been investigated for the treatment of
chronic heart failure and the evidence in favour of beta
blockade is strong. There are also diagnostic tests, for
early detection of heart failure and effective therapy
monitoring.
Beta blockers - a major breakthrough in heart
failure management When the body needs to
increase the heart rate and the pump action of the
heart, such as during exercise, a hormone called
noradrenaline is released from nerves in the heart, and
also from the adrenal glands.
In a normal person,
noradrenaline is released when it is needed, such as
during exercise. In patients with heart failure, huge
amounts of noradrenaline are released all the time to
stimulate cardiac function. This is the body's response
to the heart not working properly. By releasing lots of
noradrenaline, the sufferers' heart rate increases, but
because the heart muscle is damaged, this does not
improve the function of the heart to a great extent. In
fact, it is now known that these high levels of
noradrenaline actually further damage the
heart.
Understanding that these high levels of
noradrenaline are bad for the heart led to the idea that
blocking the effects of noradrenaline may be helpful in
heart failure.
Beta blockers were then
investigated for use in heart failure as they block the
beta adrenergic receptors in the heart through which
noradrenaline acts. For many years it was believed that
beta blockers would have a negative effect on heart
failure patients because it was felt that the increased
noradrenaline levels were useful in driving the failing
heart. This was based on the idea that if the pump was
not working properly, increasing the rate of pumping
would help – in fact we now know that this is not the
case. |
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