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CHRONIC VALVULAR DISEASE





Category: Circulatory System

Results of valve lesions. Narrowing of a valve
causes increased difficulty in emptying the chamber of the heart behind
it. Insufficiency of a valve allows the return of the blood through the
valve during the dilation of a chamber, thus increasing the amount of
blood entering the chamber beyond the normal. Either trouble causes
dilation of the chamber and compensatory hypertrophy. Enlargement of its
wall must take place in order to perform the extra work demanded
constantly, for the normal reserve force of the heart muscles can
accomplish the extra task only temporarily. This enlargement increases the
working power of the heart to above normal, but the organ is relatively
less efficient than the normal heart, as its reserve force is less and
sudden or unusual exertion may cause disturbance or failure of the
compensation acquired by the enlargement. If this loss of reserve force is
temporary, compensation is restored by further enlargement and by
diminution, by rest, of the work demanded of the heart. Any valvular
lesion, whether a stenosis (narrowing) of the outlet or insufficiency from
the moment of its origin, leads to certain alterations in the distribution
of pressure upon each side of the affected valve. If the body of the heart
itself did not possess a series of powerful compensatory aids, that is,
the power of making good a defect or loss, or restoring a lost balance, to
improve this relation of altered pressure, then every serious lesion at
its very beginning would not only cause serious general disturbances of
circulation, but very soon prove fatal. Without compensation of the power
of making good the defect or loss, the blood in every valvular disease or
lesion would be collected behind the diseased valve. The heart's reserve
power prevents to a certain extent such a dangerous condition; the
sections of the heart lying behind the diseased valve work harder,
diminish the blood stoppage and furnish enough blood to the peripheral
arteries. The reserve force is used in stenosis to overcome the obstacle,
whereas in insufficiency it must force more blood forward during the
succeeding phase through the diseased valve. To effect this increased work
permanently, anatomic changes in the heart are bound to follow. The
changes consist in hypertrophy (enlargement of the heart muscle) and
dilatation of the different chambers. Under this head, compensation, is
included the increased filling and increased work of certain heart
chambers with their resulting dilatation and hypertrophy. But this
compensation cannot last forever. It fails sometimes and certain symptoms
follow as hereafter related. Therefore persons who have valvular disease
and who have been informed that the heart has adapted itself to the
condition by enlarging of its walls and chambers and thus forming the
condition called compensation, should be very careful of their mode of
living and not put any undue or sudden strain upon the heart that might
destroy the conditions that make compensation continue. In the following
pages symptoms are given showing what happens when compensation continues
and when it fails.





Next: AORTIC INSUFFICIENCY OR INCOMPETENCY

Previous: CHRONIC ENDOCARDITIS



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