One or other of the one-way valves in the heart may become diseased
so that it does not fully open (stenosis) or does not fully close
(incompetence or regurgitation). The heart has to pump harder to eject
blood through a stenosed valve, or it has to pump twice as much blood out
if half of it leaks back. Ultimately, if the extra work gets too great, the heart
may not be able to cope and heart failure results. (See next page. 146)
Valves may become diseased by scarring from a long-forgotten attack
of rheumatic fever (rheumatic heart disease) or because of a congenital
abnormality of a valve which may not cause problems until late in life.
Rheumatic fever is now rare in Britain.
The development of open-heart surgery has dramatically changed the
outlook for those whose heart valves have been scarred or deformed. The
vast majority of cases can now be cured by surgery.
Anyone with an abnormality of a heart valve should take antibiotics
shortly before dental treatment because bacteria introduced into the blood
can settle on a weak valve. Infection of a heart valve is called endocarditis.
It is uncommon but can be serious and needs treatment in hospital for
several weeks.