Canine congestive heart failure (CHF) occurs when the dog’s heart is no longer able to pump blood to the lungs and/or body at the designed volume and pressure.
When the output of blood from the heart is decreased, the relative amount of blood entering the heart is increased. This increase in blood upstream from the heart changes the balance of fluid pressures in the upstream blood vessels and surrounding tissues. When these pressures are increased, blood fluids leave the vessels and “congest” the surrounding tissues. In the case of a decrease in output on the left side of the heart, fluid will accumulate in the lungs. If this occurs on the right side of the heart, there will be congestion in the abdomen or other body spaces.
Problems with the heart’s valves (especially the mitral valve) or a thinning of the heart’s ventricular wall are the two most common causes of CHF in dogs. In both cases the heart’s ability to pump blood is decreased. In the early stages of CHF, the dog’s body is able to compensate for a lower cardiac output. Peripheral blood vessels constrict increasing the resistance to blood flow, the heart rate will be elevated and a mechanism will be activated that causes the dog’s body to retain sodium and water. These three factors lead to an increase in blood pressure which helps to maintain normal blood circulation. Eventually, however, the decrease in cardiac output and the increase in blood pressure will lead to an accumulation of fluid in tissues and body cavities (congestion).
Clinical symptoms include but are not limited to: a cough or a belly full of fluid.
Treatment involves decreasing the work load on the heart by dilating the blood vessels and lowering the fluid load in the dog’s body. Special diets may be prescribed in an attempt to lower the amount of sodium in the dog and as a result, the dog will retain less water.
CHF is a progressive disease with no cure. Strict medical management can reduce symptoms and offer a good quality of life.
