Tricuspid Valve Dysplasia
The tricuspid valve is located between the right
atrium and right ventricle of the heart. Consisting of three irregularly
shaped flaps, the purpose is to control the backflow of blood from the
right ventricle into the right atrium during contraction of the right ventricle.
When the right ventricle contracts there is some blood, which will flow
back into the atrium. It is this flow which pushes against the valvular
flaps causing the valve to close.
During normal fetal development the tricuspid
valve flaps are adhered to the septa (wall separating atrium from ventricle).
As the fetal development progresses under normal circumstances the adhesive
bonds holding the valve open will degenerate, allowing the valve flaps
to move into their proper position.
One of the primary causes of tricuspid valve
dysplasia, is the failure of the adhesive bonds to degenerate. This lack
of degeneration can be partial or total in nature, and results in a range
of right-side heart murmurs. Dependent upon the severity of the valvular
deformation the work of the right-side of the heart is increased. If the
malformation is severe enough it can lead to enlargement of the right atrium
and ventricle. Eventually congestive heart failure can result.
Symptoms of tricuspid valve dysplasia are
dependent upon the extent of the malformation, but some of the most common
symptoms are: fluid retention, cool extremities and exercise intolerance
(possibly followed by collapse).
Tricuspid valve dysplasia in dogs is usually
congenital (present at birth). Due to the fact that this condition (when
it occurs) appears in several littermates, and tends to be more prevalent
in some family bloodlines than others - it is suspected that the tendency
to have this birth defect is hereditary. It is hoped that through screening
of breeding stock and their lineage (parents, grandparents, littermates,
aunts, uncles, etc.) efforts can be made to eliminate susceptible bloodlines
from breeding programs.
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