Common Congenital Heart Conditions

There are four valves in the heart that separate and surround the four chambers of the heart. When blood is being pushed from one chamber to the next, valves open and close according to allow blood to flow in the proper direction. When valvular defects occur, one or more of these valves do not close properly or tightly and blood will flow both forwards and backward instead of forward to the next chamber. When listening with a stethoscope, instead of “ba-bump” which is the sound tight fitting valves make when closing, the sound is more like “sh-sh” from the valve allowing blood to flow in two different directions. This unusual sound is defined as a murmur. Dogs with valvular defects usually also develop thickened cardiac muscle in certain chambers from the heart trying hard to move the blood forward.

Aortic stenosis, pulmonary stenosis and tricuspid abnormalities are three types of valvular defects seen in dogs. Some are more common in certain purebred breeds, thus a genetic component may be present. Many of these puppies may appear normal and not have any clinical signs associated with their heart defect. If the defect is severe, however, they may be smaller than their littermates (slower growth rates) or have less energy. As they become middle to older aged, the murmurs may become more pronounced and eventually may lead to congestive heart failure.

Septal defects are defined as holes between the chambers of the heart. There are atrial septal defects which are openings between the right and left atria (upper chambers of the
heart) and ventricular septal defects which are openings between the right and left ventricules (lower chambers of the heart). When these holes are present, instead of blood being contained in one chamber, it is pushed through the hole into the other chamber as well. This causes oxygenated blood to be mixed with non-oxygenated blood which causes extra stress on the heart long term.

On cardiac examination, there will be a murmur detected with septal defects just like with the valvular defects. However, the murmur heard is not because the values are not tight, but because blood is flowing between the hole into two chambers instead of one.

Some puppies with septal defects will not look any different than their normal, healthy littermates. However, some puppies may be smaller (slower growth rates) and some may have mild respiratory signs such as coughing, shortness of breath, or resting more after exercise. Again, septal defects can be found more commonly in certain purebred breeds than other demonstrating a genetic component to the condition.

Patent ductus arteriosus (PDA) is the term given to a condition for a persistent opening between the aorta and the pulmonary artery. When in the uterus, this opening is important because the puppy is not breathing air. Instead puppies in the uterus get oxygenated blood from their mother via the placenta. This opening helps distribute the oxygenated blood to various parts of the puppy’s body for survival. Once the puppy is born and begins breathing air on its own, however, the opening between the aorta and pulmonary artery is not required, and this small vessel connecting the two collapses and is eliminated. If the connection does not collapse and become eliminated, problems can occur and the puppy develops a left to right shunt of blood in the heart. This means oxygenated blood gets mixed with non-oxygenated blood causing less oxygen to be present for normal tissue health though out the body.

Puppies with PDA’s commonly have a detectable heart murmur that may be so severe, the murmur can be felt with your hand when hold the puppy around its chest. This is one of the most common congenital heart defect in purebred dogs. It has been determined to be a genetic condition in most breeds as a polygenic mode of inheritance.

Some puppies with a PDA appear normal when they are very young (ie. a few weeks old), however, respiratory signs such as coughing, exercise intolerance, poor color of the lips and tongue, and poor growth rates become more evident as they age. Death is more likely at a young age in these dogs. Surgery can be done to eliminate the opening between the aorta and pulmonary artery, however it is not a common procedure done by most general practitioners.

Because some puppies with congenital heart conditions look just like normal, healthy puppies, it is important to have a complete physical examination done by your veterinarian by the time puppies reach 6 or 7 weeks of age. A board certified cardiologist can do a cardiac examination of your puppies as well and register them with the Orthopedic Foundation for Animals’ Cardiac Certification.

By having a good examination done on a litter and having problems detected early, heartbreak over keeping the wrong puppy or unhealthy one from a litter can be prevented.