Chronic Valvular Disease

Condition Overview

This common heart disease of unknown cause affects 20 - 40% of dogs. It occurs most often in toy and small breed dogs, particularly Cavalier King Charles Spaniels, Miniature and Toy Poodles, Chihuahuas, Lhasa Apsos, Yorkshire Terriers, Schnausers, and Cocker Spaniels.

Symptoms

Chronic valvular disease is characterized by degenerative changes in the heart valves. The mitral valve is affected in nearly all cases, while the tricuspid valve in about 1/3 of cases.

Signs of congestive heart failure can be attributed to low cardiac output and lung congestion. They include a cough that occurs after exercise and/or is worse at night, lethargy and tiring easily, and fainting spells often related to cardiac arrhythmias.

All symptoms +

Causes

The valve leaflets become thickened and distorted so that the free edges of the valves no longer make contact. The cords that attach the valve leaflets to the lining of the heart may rupture allowing the valve to flap in the blood stream.

These changes will result in loss of valve function and a fall in cardiac output. When the ventricles contract, some blood is ejected backward into the corresponding atrium. This is called regurgitation. Regurgitation increases the blood pressure in the atrium and causes it to enlarge. Because the mitral valve is invariably involved, chronic valvular disease is also sometimes called mitral valve disease or mitral regurgitation.

Diagnosis

A common sign of chronic valvular disease is a loud heart murmur heard over the left side of the chest. A chest X-ray, ECG, and echocardiogram may show an enlarged left atrium, thickened valves, or a ruptured cord (muscle band). If the tricuspid valve is involved, there will be a loud heart murmur heard over the right side of the heart. It is important to exclude heart worms as a cause of a right-sided heart murmur.

Treatment

Many dogs with uncomplicated heart murmurs associated with chronic valvular disease remain asymptomatic for years. The disease, however, is chronic and progressive. Treatment should be started at the first signs of impending heart failure (coughing, easy tiring). The outlook depends on how far the disease has progressed and the general health and age of the dog.

Prevention

The only prevention is early identification of the condition.

Support

Please contact your veterinarian if you think your pet may have this condition.