A careful examination of puppies by a veterinarian is recommended at 6 weeks of age. Many puppies are born with a slight heart murmur (or puppy murmur) that clears up by itself after 4-6 months. In many cases, vets will simply recommend a later checkup, just to be sure that the condition has resolved itself. Congenital defects are those that have been present since birth. They are comparatively rare, accounting for only 5% of the cases seen by vets.
Chronic valvular disease can be thought of simply as 'leaky valves', caused when the moving parts of the heart valves thicken and harden with age. The result is more or less the same as when a valve in your central heating system starts to wear out: increasingly poor circulation. Valves may thicken or harden with age. This can either restrict bloodflow, or allow blood to 'leak' back past the valve. If any valve is affected in this way, it will compromise the heart's ability to pump blood. Although valvular disease can affect any dog, smaller breeds tend to be more prone.
Patent Ductus Arteriosus (PDA) At birth, mammals must adapt from living in a fluid environment (the amniotic fluid) and acquiring oxygen through the mother's blood, to breathing air and acquiring oxygen through their own lungs. The ductus arteriosus is very important in the adaptation process. This is a small communicating blood vessel between the pulmonary artery (which carries blood to the lungs), and the aorta (which carries blood to the rest of the body). Before birth, most of the blood from the fetal heart bypasses the fetal lungs via the ductus arteriosus. The lungs gradually become functional fairly late in fetal development. At birth, the blood supply from the mother is of course cut off, the dog (or other mammal) begins breathing on its own, and blood flow through the ductus arteriosus decreases dramatically. Within a few days, the ductus closes off completely.
Where the ductus does not close, the dog is left with a patent ductus arteriosus (PDA). The extent to which this affects the dog depends on the degree of patency, or opening, of the ductus. PDA is the most commonly diagnosed congenital heart defect in dogs. It occurs in many breeds and is seen more often in females. Yorkshire Terriers are one of the breeds with an increased risk for PDA.
