|
Normal heart
The heart is a muscular pump; its function is
to pump blood through the body. The heart can be divided into two sides;
right and left. Each side has two chambers; the atrium and the ventricle, separated
by one-way valves which maintain the blood flow in the correct direction. The
right atrium receives blood from the veins in the body, which is relatively
low in oxygen. It passes from the right atrium into the right ventricle and
is then pumped to the lungs to collect oxygen. From the lungs oxygen-rich
blood passes through the left atrium into the left ventricle. It is pumped
out through a large artery called the aorta to the organs and the other
tissues in the body to deliver oxygen. Blood then flows back through the
veins to the right side of the ventricle and the cycle begins again.
At rest, the hearts beats on average 60 to 80
times a minute and pumps approximately 5 litres of blood (1.3 gallons) per
minute through the body. During exercise, the heart may pump as much as 25
litres (6.5 gallons) per minute.
Heart failure
In heart failure, the heart muscle becomes too
weak to pump enough blood around the body to the vital organs, so depriving
them of oxygen and vital nutrients. Heart failure most commonly results
from one or more heart attacks when part of the heart muscle is
replaced by scar tissue. This nearly always
occurs in the left ventricle.
|
|
The heart muscle
expands over time and pumping becomes increasingly difficult. Less blood goes
out to the body via the aorta and more blood stays in the lungs which makes
people feel short of breath.
This is noticed first during exercise, then
later also at rest, particularly at night, when the patient lies flat. This
not only makes people feel tired (less oxygen to the body muscles), it also
fools the kidney into believing that the body does not have enough blood. The
kidneys then hold on to salt and water, and as a result excess fluid builds
up in the body straining first the left and then the right side of the heart.
As the right side of the heart starts to fail, pressure builds up in the
veins and fluid accumulates in legs and ankles, and in more severe cases in
the abdomen, leading to a bloated feeling and loss of appetite.
Another frequent cause of heart failure is
long-standing high blood pressure (hypertension). This causes the
muscle of the left ventricle to thicken so that it becomes inflexible and
difficult to pump. If the blood pressure is not reduced the heart muscle will
get thicker and thicker, and a similar situation to that described above with
heart attacks will occur.
Although heart failure is an extremely serious
condition, many sufferers can improve their condition with lifestyle changes,
appropriate medicines, device therapy, or surgery.
|
