Canine degenerative valve disease is a serious and very common cardiac disease. As the name suggests, it is caused by deterioration of one or more heart valves. About a third of dogs over the age of 10 and 75% of dogs older than 16 have some form of heart disease
The heart is divided into four chambers. The right side of the heart receives oxygen-poor blood from the body and pumps it into the lungs where it becomes oxygenated; the left side of the heart receives the oxygenated blood from the lungs and pumps it throughout the body.
The two sides of the heart are separated by a dividing wall of muscle called the septum. The upper and lower chambers of the heart (the atria and ventricles, respectively) are connected by orifices, or valves. These two “atrioventricular” valves are one-way and should close properly.
This prevents blood flowing back through the system when the heart contracts. The valve between the right atrium and right ventricle is called the tricuspid valve and the valve between the left atrium and left ventricle is called the mitral valve. The heart also has two “semilunar” valves that separate the right and left ventricles from the pulmonary artery and aorta (respectively the pulmonary and aortic valves).
In dogs, it is usually the mitral valve that deteriorates, though sometimes several valves become damaged. The damaged valves no longer close properly, allowing the blood to flow back through. This has many adverse effects on cardiac health.
First of all, congestion can occur in the blood vessels leading to the heart. Damage to the mitral valve results in this constriction in the pulmonary veins; damage to the tricuspid valve results in constriction in the vena cava. Mitral valve damage can cause pulmonary oedema (fluid in the lungs) and tricuspid valve malfunction can lead to ascites, an abnormal build-up of fluid in the abdomen.
This regurgitation tires the heart, since some of the blood flows in the wrong direction and the heart has to work harder to pump a constant volume of blood. It also causes atrial and tissue damage upstream, as well as considerable oxidative stress.
All dog breeds can be affected by this disease, but it is more common in small breeds, especially Cavalier King Charles spaniels, where the symptoms sometimes appear early in life.
If you notice any of these symptoms, make an appointment with your vet as soon as possible. Unfortunately, symptoms do not appear until the disease is very advanced and treatment may be ineffective.
Here’s a tip to detect mild breathing difficulties that may be a sign of early cardiac decompensation (inability of the heart to maintain adequate blood circulation): take your pet’s resting respiratory rate (RRR). When your dog is asleep, it should breathe slowly and steadily. If it is breathing more than 30 times a minute while at rest and it is not a warm day, you should seek veterinary advice.
Only your vet can detect canine degenerative valve disease at an early stage. That’s why an annual check-up is essential, especially for elderly dogs. By listening to your dog’s heart with a stethoscope, your vet may be able to detect a heart murmur (a sound caused by turbulent blood flow in and around the heart) even though your dog is not yet showing any symptoms. But listening with a stethoscope is not enough in itself to make a definitive diagnosis. An echocardiogram (an ultrasound of the heart) and chest X-rays are also required to confirm the disease.
This heart check-up also enables the vet to give a prognosis based on how advanced the disease is and to decide on the most appropriate treatment to keep your dog in good shape for as long as possible. Regular follow-ups will be needed, as sometimes the disease progresses rapidly. Unfortunately, it is impossible to make predictions, even for specialist vets.
It is now known that even a dog not yet showing symptoms may need treatment, because irreparable damage first occurs at cellular level and its devastating effects are not immediately apparent. Starting treatment before any symptoms appear can give your dog up to two years of normal life, so don’t delay!
If your dog is overweight, the first step is to help it slim down to ease the strain on its heart by feeding it a diet high in antioxidants and good-quality protein and low in salt. Miloa’s Cardio Supp TM which is rich in antioxidants, taurine, omega-3 fatty acids and coenzyme Q10, slows the rate of damage. Olive leaves, Sophora japonica and pomegranate are powerful allies in protecting your pet’s cardiac health.
If your pet is already showing symptoms, there’s no need to panic, as specific medicines are available. Some help the heart to contract better; others decrease resistance to blood flow in the vascular system, lower hypertension (high blood pressure) or reduce pulmonary oedema.
This disease usually progresses slowly. The earlier it is detected, the longer your pet will live. Unfortunately, even dogs that are properly followed up and stabilised with appropriate treatment can die suddenly, which is why they should be closely monitored and have their RRR checked daily.
Dr Maud Pivont
General practitioner | Qualified specialist in veterinary ophthalmology