The heart functions to maintain life by supplying blood (and thus oxygen and nutrients) to the organs and tissues. When compromised, severe illness and possibly death, can occur.
Heart disease encompasses many different problems that affect the heart in different ways:
Congenital heart disease occurs when animals are born with abnormalities of the heart muscle or valves. The most common congenital abnormality in dogs is a patent ductus arteriosus (PDA). A PDA is a connection between the pulmonary artery (which carries blood to the lungs) and the aorta (which carries blood to the rest of the body) that doesn't close when the animal is born. This results in a significant portion of unoxygenated blood being delivered to the organs which in turn requires the heart to work that much harder to oxygenate the tissue of the body. In turn, the heart starts to fail which results in coughing, difficulty breathing, and weakness. Depending on the size of the dog, a PDA can be corrected by either surgical closure of the patent duct OR by non-surgical placement of a coil that closes the duct over time.
Acquired heart disease develops after birth and can vary from "leaky" hard valves to a dilated heart muscle. Degenerative valve disease (DVD), also known as valvular insufficiency, regurgitation, or endocardiosis, is the gradual degeneration of one of the valvues of the heart (most commonly the mitral and tricuspid valves) which results in an "inefficient" valve. This inefficient valve "leaks" some blood backwards while trying to pump blood forward to the rest of the body. This "leakiness" causes an audible murmur that can be heard on physical exam. DVD accounts for 75% of acquired heart disease in dogs but the most common breeds affected are: Miniature poodles, Cocker Spaniels, Miniature Schnauzers, Dachshunds, and Cavalier King Charles Spaniels. In many patients, DVD progression is slow and has minimal impact on the animal's quality of life. However, if the regurgitation (backflow) of blood is severe enough, the heart chambers will enlarge and increased pressure develops in either the lungs or the abdomen (depending on which valve is involved). This results in coughing, shortness of breath, increased breathing rate, lethargy, exercise intolerance, lack of appetite, abdominal distension, and weight loss.