Valve diseases
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 (regurgitation or incompetence).
The heart has to pump harder to eject blood trough 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. Valves may become disease by scarring from a long-forgotten attack of
rheumatic fever or because of a congenital abnormality of a valve which may not
cause problems until late in life. Rheumatic fever has recently increased in
Mediterranean countries, especially in
Northern Africa ones.
The development of open-heart surgery has
dramatically changed the outlook for those whose valves have been scarred or
deformed.
Vlves
may be biological or mechanical. If biological they may be made from bovine or
porcine pericardium, or aortic valves (xenograft). The mechanical valves consist
of an orifice surrounded by a sewing ring and filled with an occluder. The
occluder may be a ball, a tilting disc or two leaflets.
Main models of artificial valve
|
Biological |
Autograft
(pulmonary to aortic switch Homograft
(human cadaver aortic valve) Xenograft
porcine, such as Carpentier-Edwards, Hancock intact Unstended
porcine, such as Carpentier-Edwards, Hancock. Intact Unstented
porcine, such as Edwards Prima, St Jude Totonto Bovine
pericardial, for exampleMitral Medical, Baxter
|
|
Mechanical |
Caged
ball, for example, Starr-Edwards Caged
disk (withdraun), for example, Beall Caged
disc (withdrawn), for example Beall Tlting
disc, for axample, Bjork-Shiley, Medtronic Hall, Omnicarbon, Omniscience,
Sorin monostrut Bleaflet,
i.e: St. Jude Medical, Carbomedics, Jyros |
Anyone
with an abnormality of a heart valve should take antibiotics shortly before
surgery or any kind of endoscopy. Antibiotics need also before dental treatment
because bacteria introduced into the blood can settle on a weal valve. Infection
of a heart valve is called endocarditis
Echocardiography
assesses the following aspects of an artificial valve:
q
Imaging
q
Forward flow
q
Regurgitation
q
Complications (thrombus,
endocarditis, valve abscess)
q
The
rest of the heart
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