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Categories: 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 ord
r 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.