Blood in the arteries is under pressure, like water in a hose-pipe with
the tap turned on. Blood pressure is pulsatile, rising to a systolic peak with
each heart-beat and falling to a diastolic trough in between beats. Just as
the pressure in the hose pipe (the strength of the jet) gets higher if the tap is
opened more or if the hose-pipe is narrowed, so the blood pressure is altered
by changes in the amount of blood ejected by the heart with each beat or by
the calibre of the arteries. The amount of blood the heart pumps around the
circulation varies enormously with everyday activities. Fortunately the body
can adjust the resistance of its arteries to prevent the blood pressure
swinging too wildly. Nevertheless blood pressure will normally vary to
some extent. Your doctor will, therefore, usually measure your blood
pressure more than once to get an average reading.
Some people run higher blood pressures on average than other people,
in much the same way as some people are taller or fatter than others. In
most cases we cannot find a definite cause-though in a very small minority
of cases there is a specific cause such as kidney disease.
High blood pressure is particularly dangerous because it does not itself
cause any symptoms, despite the commonly held view that it causes
headaches, giddiness, flushing and nose bleeds. It does, however, put an
extra strain in the longterm on the heart and arteries, it causes premature
ageing and hardenin of the arteries and it encourages atheroma. The higher
the blood pressure, the more likely eventually is a heart attack or a stroke.
However, high blood pressure can generally be lowered quite easily with proper treatment. One of the most valuable results of recent research has been
the development of drugs which can lower blood pressure without causing nasty
side-effects. These generally need to be continued indefinitely and usually do
not interfere with continuing a fully active normal life.
High blood pressure should be regarded as a ‘risk factor’ for
cardiovascular disease that can be dealt with once it is recognised. It should be
regarded as a measurement and not a disease. It is quite common (5-10% of
adults have high blood pressure), but it is ‘silent’ and can be recognised only by
having it measured. Only half the people with high blood pressure are aware of
the fact (more routine checks would help to discover the others) and only half of
these are having proper treatment (often because they have not fully understood
the need.) You should have your blood pressure checked every few years and
more often if on the contraceptive pill or if the readings are at the higher end of
normal.