Dog Manual


Heart Diseases


Even the most competent specialist in canine diseases often finds it difficult to establish clinical diagnoses of the ailments of the heart. It is apparent, therefore, that any detailed description of heart diseases would be of little value to the general reader. However, the intelligent person in the modern world should have some idea of what some of the terms associated with heart diseases signify, since they are so commonly mentioned in everyday conversation.

The heart is covered by a double membrane which forms a sac around it. This membrane is called the pericardium, and the sac is called the pericardial cavity. An inflammation of the pericardium is called pericarditis. Where a watery fluid accumulates in the pericardial cavity as a result of some inflammatory process, the condition is called hydropericardium. When blood accumulates in the pericardial cavity, the condition is called hemopericardium.

The heart of dogs, as well as that of man, consists of four chambers. Between these chambers are structures known as valves. When the blood is pumped from one chamber to another and from there to the rest of the body, it is the function of these valves to block off the backward flow of blood so that there will be no interference with the impetus which that blood has obtained from the heart. When there is improper closure of the valves, the condition is known as valvular insufficiency. This will give rise to a sound commonly called a heart murmur. Sometimes, when the valves are relaxed, they may have some involvement whereby they do not permit proper flow of blood through the blood chambers. In other words, they tend to remain nearly closed all the time. This condition is called valvular stenosis.

The muscle tissue of the heart is called the myocardium. An inflammation of this structure is called myocarditis. The lining membrane of the heart chamber is the endocardium. An inflammation of the endocardium is called endocarditis. Where there is an abnormal increase in the size of the heart due to the increase in the quantity of muscle tissue, the condition is called hypertrophy of the heart. When the heart increases in size due to the enlargement of the heart chambers, the condition is called dilatation of the heart. When the heart is ruptured due to injury or any other cause, then the designation rupture of the heart is applied to the involvement.