The function of the heart is to pump the blood to the lungs and from there, loaded up with oxygen, to pump it to the rest of the body where the oxygen is used up. In congestive heart failure, the heart is unable to adequately circulate blood. One of the primary reasons in dogs that the heart begins to fail is heart valve degeneration.
The disease process and symptoms differ based on which part of the heart is affected. Oxygen depleted blood is returned to the heart and enters the heart into the right atrium. It then travels into the right ventricle, is pumped through the lungs, then enters the left atrium, and passes into the left ventricle which then pumps the blood to the body.
With right sided heart failure, the right atrium and ventricle are not working effectively, and blood gets backed up in the systemic circulation, where the blood traffic becomes congested. As a consequence fluid seeps into, and accumulates in the abdomen (ascites), causing discomfort and pressing on the surrounding organs. Fluid may also leak from veins into the limbs, causing swelling, known as peripheral edema.
With left sided congestive heart failure - the more common kind -, the blood flow gets backed up in the lungs. Fluid seeps into the lungs, causing pulmonary edema. With time the heart will become enlarged and press on the surrounding airways, causing irritation. The most common clinical signs are reduced energy level and coughing. You may notice that your dog does not enjoy going for walks anymore, lags behind and doesn't play with her toys. Her breathing may appear rapid and more labored.
Physical exam, x-rays, electrocardiogram and an ultrasound of the heart will offer great information and will help your veterinarian and veterinary cardiologist make a diagnosis and create a treatment plan for your dog. Close monitoring may be needed after initiating therapy, as the medications prescribed can affect other internal organs.
When therapy is successful, you will notice a decrease in coughing and an improved ability to breath. As a rule of thumb, your veterinarian will ask you to report if the breathing rate is faster than 40 breaths per minute at rest.
Much progress has been made in the treatment of heart failure and with proper care and monitoring, your dog's quality and length of life can be greatly improved.