160 DISEASES OF THE CIRCULATORY APPARATUS 



Valvular Diseases of the Heart; Chronic Endocarditis; Valvular Defects. 



General Notes on Valvular Defects. — By valvular defects we under- 

 stand such anatomical alterations in the valves and openings as lead 

 to an irregularity in the circulation of the blood, becoming apparent by 

 visible symptoms in the pulse or general condition; but those slight val- 

 vular defects so often seen in post-mortems and never noticed during 

 life are not to be considered. 



Valvular defects appear in two forms: first, when the valves close 

 impei'fectly; second, when the openings become contracted, causing 

 stenosis. Imperfect closure of one valve causes a certain amount of 

 blood to flow back into the portion of the heart from which it has just 

 come; for instance, when there is imperfect action of the mitrals or of 

 the tricuspids in systole, part of the contents of the ventricles rushes back 



Fig. 67. — Diagram of the blood circulation. 



into the auricles, and when there is insufficient action of the semilunar 

 valve in the diastole, a part of the blood that has been thrown into the 

 artery returns into the chamber again. 



Stenosis of one opening retards the passage of blood, when we have 

 a contraction of an arterio-ventricular opening. At the time of diastole 

 the blood is kept back at the entrance of the affected ventricle, and it 

 is imperfectly filled, while in the aortic opening in pulmonic stenosis the 

 exit of the blood out of the ventricles (Fig. 67) in the systole is retarded. 

 In any of these conditions there is imperfect heart action; every defect of 

 an arterial opening interferes with perfect ventricular action and every 

 defect in a venous opening causes a corresponding lessening of power in 

 the auricle. 



An abnormal pumping of the blood in this manner is sure to cause 

 more or less disturbance of the entire organism, but there are certain 

 compensatory processes in the heart itself that tend to overcome this. 

 As a consequence of the impaired flow, the heart muscle is worked much 

 harder and becomes hypertrophied (compensating heart hypertrophy). 



