Blood flows into the right side of the heart. The right ventricle then pumps the blood into the lungs where it picks up oxygen. The blood then flows into the left side of the heart where it is pumped back out into the body. As the blood flows into the different chambers of the heart, valves close behind it to ensure the blood continues to flow in the correct direction. The sound that is heard when listening to the heart is the sound of the valves slamming shut.
If the valves do not operate properly, some of the blood will be pushed backwards. If the valve fails that closes behind the blood flowing into the right side of the heart, then blood will back up into the liver and abdomen and cause “ascites”. If the valve fails that closes behind the blood flowing into the left side of the heart, then blood will back up into the lungs.
Congenital heart disease can occur in any size dog. Typically, the heart valves do not form properly, leading to failure to function properly. The valves don’t seal the openings; and therefore, you can hear the blood leaking through the valve making a ‘whooshing’ sound. This sound is referred to as a murmur. Diagnoses of a heart murmur is made by using a stethoscope to listen to the heart. Many dogs can live for years with a murmur without developing CHF.
Congestive heart failure (CHF) is a very common disease in dogs. CHF can occur in both large and small breed dogs although the underlying causes vary significantly. In small breed dogs, the most common cause is chronic dental disease. The bacteria in the mouth set up residence on the heart valves. Eventually, the valve begins to thicken and function improperly, leading to CHF. In large breed dogs, the most common underlying cause is due to the heart being over worked. This leads to a thickening of the heart wall and the failure of the heart to properly pump the blood. Additionally, severe heartworm infestations can lead to CHF in any size dog.
Symptoms of CHF depend on which side of the heart is affected. Right sided CHF will lead to ascites. If the blood is being backed up into the abdomen, then the belly will start to fill with fluid and become distended. If the blood is being backed up into the liver, then you can start to see signs of liver failure (jaundice, vomiting, loss of appetite, etc.).
Left sided CHF will lead to blood being backed up into the lungs. The dog will usually wheeze or cough. The cough is often productive, meaning that they cough up fluid.
With both types of CHF, the dog will have a decrease in energy and possibly a loss of appetite.
Treatment of CHF also depends on the underlying cause. It can include: medication to increase heart muscle contractions, diuretics to draw the extra fluid out of the lungs, liver, or abdomen, and a special diet.