The condition becomes progressively worse due to the progressive demands made upon the heart, and death takes place after some days or months or years, the time depending upon the degree of the imperfection.
Much of the damage of the heart in later life is due to infection.

The valves of the heart are a favorite place for attack by certain sorts of bacteria which get into the blood.

This is due to the prominent position of the valves which brings them in contact with all the blood in the body, the large extent and unevenness of the surface and to the rubbing together and contact of their edges when closed.

At the site of infection there is a slight destruction of tissue and on this the blood clots producing rough wart-like projections.

The valves in some cases are to a greater or less extent destroyed, they may become greatly thickened and by the deposit of lime salts converted into hard, stony masses.