The body has an immune system that protects from foreign invaders that can cause disease and infection, however, if with an autoimmune disease, the immune system attacks itself by mistake, causing illness.

Atrioventricular (AV) valve dysplasia is a developmental malformation of the mitral or tricuspid valve in the heart. Signs include exercise intolerance, accumulation of fluid in the abdomen, weight loss, and stunted growth. Difficulty breathing or collapse may occur if congestive heart failure develops. Treatment of AV valve dysplasia is focused on managing signs of congestive heart failure and/or disturbances in heart rhythm, generally using medications.

Atrial fibrillation describes very rapid contractions or twitching of the heart muscle, specifically in the atria. Most of the time, atrial fibrillation in dogs occurs secondary to heart disease. In some large breed dogs, atrial fibrillation occurs as a primary heart problem. Most dogs who develop atrial fibrillation have underlying heart disease, so the signs that are observed are related to that disease and may include exercise intolerance, cough, or difficulty breathing. Treatment varies depending on whether the dog has primary or secondary atrial fibrillation. Your dog will need to be monitored on a regular basis.

This handout explains atopic dermatitis (atopy) in dogs, a form of allergic skin disease brought on by an abnormal response to allergens in the environment. The clinical signs, diagnosis, and treatment are outlined.

This handout summarizes atlantoaxial (AA) luxation, a condition in which instability or excessive movement is present between the first two vertebrae within the neck. Atlantoaxial luxation can be caused by trauma, hereditary factors, or a combination of these two factors. The most common sign of AA luxation is neck pain, though severely affected dogs may lose their ability to breathe due to paralysis of the diaphragm.