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.

[Circulatory diseases 343]

Aortic insufficiency or incompetency.—­The valves are not doing their work thoroughly.

Symptoms.—­They are often long absent; headache, dizziness, faintness, flashes of light, difficult breathing, and palpitation on exertion, and pain in the heart region may occur early.  The pain may be dull and localized, or sharp and radiating to the neck or left arm.  When compensation fails, we have difficult breathing, which is worse at night, swelling of the eyes and feet, cough, anemia.  Sudden death is more common in this than with any other valvular disease.  You can hear a soft blowing sound by listening with your ear.

Narrowing (Aortic Stenosis).—­Caused by chronic endocarditis, etc.  Their valve segments are usually adherent to each other by their margins and are thickened and distorted.

Symptoms.—­When compensation is gone, diminished blood in the brain causes dizziness and faintness.