In older pets, the most common heart problem encountered in veterinary medicine is an acquired disease of the aging heart valves called Chronic Valvular Disease (CVD). It usually involves the mitral valve, which, in essence, is a poorly functioning valve that comes with age and deterioration of the tautness of that valve. When that valve doesn’t close properly, that allows a quantity of blood to be improperly ejected and go into a different heart chamber. When the heart works to put blood where it should go and it doesn’t go there, it’s inefficient. It means that the heart has to work harder to get the correct quantity to the proper places. Therein lies the problem: The further this lack of proper pumping progresses, more problems can occur.
Picture the valve being a flap that is anchored in place by miniature cables to the heart wall. When young and healthy, the flaps snap together in an instant and close the hole completely, not allowing any backflow or leakage. Those cables control the opening and closing of that hole. As your dog ages, the valve flaps can become smaller and stiffer and some of those cables can snap or become too stretchy. In their deteriorated state, the valves will not close the opening completely, allowing leakage of blood.
That leakage is usually audible on examination with a stethoscope as a swishing sound. In a healthy heart, you just hear, thud, thud. With CVD, you hear thud-swish-thud, thud-swish-thud, indicating a heart murmur, usually the first clue that your dog has CVD. Lethargy, inability to exercise, trouble breathing and coughing also are symptoms. Your dog can have CVD for a long time and not have any symptoms at all—just the murmur. On the other hand, it also can advance to heart failure. When muscles work, they get bigger and the same goes for heart muscle. Working to compensate for the inefficient mitral valve will cause the heart to enlarge, taking up more space in the chest cavity and pressing on the bronchi and trachea. I used to think of these murmurs as incidental, like some murmurs in humans. But many years ago, three patients in one month had complications due to their leaky valves. Now, I track these murmurs much more closely with repeated visits for a listen or follow up X-rays to check for enlargement progression.
This disease affects older, smaller breeds of dogs most frequently. There doesn’t seem to be a sex predilection but one study showed that boys may get it at a younger age. Cavalier King Charles is a breed that is susceptible to inheriting CVD.
Diagnosing CVD follows the same path as many other diseases: Bloodwork, X-rays, and an ECG (electrocardiogram) are the first three steps. But the best way to diagnose the problem is with Doppler echocardiography, which can pinpoint leakage and the defective valve and will eliminate the need for an ECG. The blood sample will give you a baseline for values that may need to be tracked in the course of treatment, and can illuminate the effects of the inefficient heart on other organs. The ECG can help describe the electrical problems possibly created by an enlarged heart. The radiograph will help to define size changes in the heart.
To treat or not to treat is somewhat controversial, especially in the early stages. Some vets will recommend treating if there is confirmed CVD and heart enlargement, some won’t. Most won’t treat without heart enlargement and track the size of the heart with follow up X-rays or Echos before making further recommendations. So, treatment depends on differing disease stages: none for simple, early disease and big time therapy for congestive heart failure. All manners of drugs are used to treat heart failure and your vet will guide you there. Other drugs are used to treat related signs or symptoms such as the secondary cough mentioned earlier. All dogs with CVD can benefit from weight loss and some can benefit from special diets that are lower in sodium.
This is a disease that is usually suspected much prior to clinical symptoms manifesting themselves. It’s a classic example of why annual or twice a year examinations are more important than almost any other thing done on a routine visit. If you think little ole ‘Valentine’ is just aging and slowing down and doesn’t need to see the doctor anymore, just whittling away the last months at home, rethink that. You may just get your ‘puppy’ back with an early intervention for a dog with Chronic Valvular Disease. LN