Valvular Dysfunction

Diagnosis, Overview, and Prognosis

The prognosis is poor for animals diagnosed with valvular dysfunction, the most common type of heart disease which affects 20 – 40% of dogs (Eldredge, et al., 2007). “Many dogs with uncomplicated heart murmurs associated with chronic valvular disease remain asymptomatic for year. The disease, however, is chronic and progressive” (Eldredge, et. al, 2007, p. 334). Valvular dysfunction is much more common in dogs than in cats – it is reported that .2 – 1% of cats are affected by congenital valvular defects. A heart with a deformed or faulty valve does not pump efficiently and allows fluid to swish back and forth between chambers of the heart, causing fatigue, exercise intolerance, and enlargement of the heart muscle due to increased stress. A heart that is pumping in this condition can allow some fluid to back up into the lungs, causing the animal to cough when over-stimulated. Valvular deficiencies can be congenial (from birth), and can also develop later in life. “A valve’s tissue is like skin… With age, the tissue starts to fail. The collagen components within the valve don’t do their job, and the valve starts to leak” (Dr. Marc Kraus, DVM, as stated in Ewing, 2009, p. 8). According to Eldredge, et. al., (2007), the mitral valve (in the left chamber of the heart) is affected in nearly all cases, and the tricuspid valve (in the right chamber of the heart) in about one third of the cases. Valve dysplasias (congenital deformations) have a very poor prognosis. Affected dogs are at risk of congestive heart failure and sudden death. The literature suggests that valvular dysfunction can be treated to extend and increase the quality of life, and many dogs with mild valvular dysfunction can remain asymptomatic for years. However, make no mistake – the disease is chronic and progressive and cannot be “cured.”

Symptoms

Dogs or cats with valvular dysfunction may display any or all of the following symptoms:

• heart murmurs
• poor circulation – which can be determined by looking at the color of the gums and tongue. Deep pink is a sign of normalcy, whereas a grey or bluish color is a sign of inadequate oxygen in the blood (Eldredge, et. al., 2008). Some dog breeds, like Chow Chows for example, have naturally purple-colored tongues. Know what is normal for your pet.
• exercise intolerance – the dog or cat may display a lack of interest in walks or movement. This can be harder to detect in cats, as they are much better at masking their pain and regulating exercise than dogs are. Often by the time cats start showing overt symptoms, they are already in an advanced state of heart failure.
• fainting spells – after a bout of increased exertion or excitement, the dog or cat may collapse as if having “passed out” and get up shortly thereafter.
• coughing – in dogs, during or after exercise, which may get worse at night. Literature suggests that this symptom is not as common for valvular disease in cats – if a cat coughs, it is most likely a sign of feline bronchitis or asthma (Eldredge, et. al., 2008).
• swollen abdomen – called ascites, occurs when the dog or cat is in a state of congestive heart failure. The swollen abdomen is caused by the heart pumping inefficiently, which causes fluid to back up into the lungs and other vital organs.

Treatment

• restricting the animal to moderate exercise levels, taking extra care especially in hot weather, as dogs rely primarily on their circulatory system to cool them (dogs do not sweat like we do!).
• low salt diets or other special cardiac formula veterinary diet – See Heart Disease: Resources: Diet
• medication therapy – typically a diuretic to keep fluid levels low, +/or ACE inhibitors
• surgical intervention for valvular dysfunction requires open heart surgery, which is not readily available in veterinary medicine (Ewing, 2009). There is only one institution in the United States that offers veterinary open heart surgery – See Heart Disease: Resources: Veterinary Cardiology Resources