CHAPTER II. 

 DISEASES OF THE HEART. 



VALVULAR INSUFFICIENCY AND STENOSIS. 



Definition.— A pathological or anatomical defect in the 

 valves and openings of he heart leading to an irregularity 

 in the circulation of the blood. These conditions are very 

 common in small animals, especially the dog, where often 

 quite extensive alterations in the valves are found on autopsy 

 which failed to produce any marked symptom during life. 

 However, when severe forms of insufficiency or stenosis 

 occur, they are characterized by a marked disturbance in the 

 heart action, circulation of the blood and the general condi- 

 tion of the animal. It is often very difficult and sometimes 

 impossible to differentiate clinically between the various 

 valvular and ostial defects which are found on autopsies. 



Insufficiency .—In general, this condition occurs in two 

 forms: (a) Imperfect closing of the valves which permits 

 a portion of the blood at the contraction of the heart muscle 

 to flow back into the chamber from which it came. This 

 defect may exist in the atrioventricular valves or in the semi-' 

 lunar. Improper closing of the semilunar valve allows a 

 portion of the blood which has been forced into the artery 

 to again return to the chamber during diastole; or imperfect 

 closing of the mitral or tricuspid valves during systole allows 

 a portion of the blood to flow back into the auricles again 

 from whence it came. In the early stages of insufficiency, 

 owing to certain compensatory processes, no marked symp- 

 toms will be observed. However, as soon as the heart is not 

 capable of performing the increased labor from lack of nutri- 

 tion, increased disturbance in the valves, or general weakness 

 from anemia, cachexia, etc., marked disturbance in the 

 general circulation will soon become evident. These are 



