Your veterinarian has just informed you that your dog or cat has congestive heart failure. What on earth does that mean, what can be done and what can I expect to happen? Simply put congestive heart failure (CHF) refers to the retention of fluid due to severe heart disease. If the left side of the heart is primarily affected, fluid is retained in the lungs or pleural cavity (space around the lungs). When the right side is primarily affected, fluid accumulates in the abdomen. In smaller dogs the most common heart disease that can lead to congestive heart failure is myxomatous mitral valve disease (MMVD). In this disease, the valves between the atria and ventricles become deformed (the cause is unknown), leading to a leaky valve. In larger dogs and also in cats, we more commonly see cardiomyopathies (diseases which affect the heart muscle).

The symptoms of congestive heart failure can vary depending on which side of the heart is primarily involved. Left sided CHF results in decreased oxygen in the blood due to lower absorption in the lungs. In humans this is described as shortness of breath. Animals cannot tell us when they experience shortness of breath, but you may notice a decrease in exercise ability and an increased respiratory rate (faster than normal breathing). In dogs (but not cats) with left heart failure coughing is a common symptom and fainting episodes (syncope) as well. With right sided CHF the most common finding is fluid accumulation in the abdomen (ascites). Cats with cardiomyopathy often present with seemingly acute signs of CHF (most commonly severe breathing difficulty). Early symptoms are often missed in cats because of their sedentary lifestyle.

A diagnosis of CHF by your veterinarian relies on the symptoms, findings such as a heart murmur and/or abnormal rhythm on auscultation (with a stethoscope) and x-rays to evaluate the heart size and look for fluid in the lungs. Additional information about heart chamber dilation, contractility etcetera, can be obtained by performing a cardiac ultrasound examination and this will often be advised for dogs and is essential to correctly diagnose cats with cardiomyopathy.

When it comes to treatment several medications can be used depending on what disease is causing the CHF and the stage of the disease. Most commonly diuretics (water tablets), vasodilators and pimobendan (a drug that primarily increases contractility) will be prescribed.

Smaller dogs with mitral valve disease can often be managed reasonably well with medication for variable periods of time. About 20% of these patients will still be alive after two years and some individuals much longer. Unfortunately, the cardiomyopathies generally have a poorer prognosis, especially in cats.