Heart failure is the inability of the heart to sufficiently circulate blood to meet the body’s needs. This usually means there is failure of either the heart muscle or a valve inside the heart. The most common cause of heart failure in dogs is mitral valve insufficiency. It is more common in small breeds. Mitral valve disease is estimated to account for up to 80 percent of all dog heart disease cases. This type of failure usually has a slow progression and dogs generally live for quite some time after diagnosis.
Another type of heart failure is dilated cardiomyopathy, which occurs most commonly in large breed dogs and often results in sudden heart failure and death. In humans a “heart attack” usually refers to myocardial infarction. This is death of the cells in an area of the heart muscle usually due to obstruction of the coronary blood vessel that supplies oxygenated blood to the heart muscle. Although this can occur in dogs, it is not common.
More likely, dogs develop congestive heart failure due to mitral valve insufficiency or dilated cardiomyopathy. A heart murmur is simply an abnormal sound of the heart and is detected by listening with a stethoscope. Murmurs suggest some kind of heart problem, but certainly do not determine the exact problem or the severity of the heart condition.
The mitral valve actually prevents blood from flowing back into the heart after each contraction. The valve must withstand tremendous pressure throughout life. Therefore, it may begin to fail or “leak” as the dog ages. As time goes on, the leak becomes more severe and as more blood leaks back into the heart, the pumping efficiency is reduced. Eventually congestive heart failure occurs. The most common symptom of congestive heart failure is persistent coughing accompanied by difficulty breathing. This is due to the accumulation of fluid in the lungs called pulmonary edema.
Another type of congestion can occur with fluid accumulating in the abdomen called ascites. Ascites causes the dog to have an enlarged abdomen. Fortunately, ascites is not as life threatening as fluid in the lungs.
Additionally, most dogs with heart disease will fatigue more easily, have reduced stamina and not engage in playing or walking as they once did. Congestive heart failure can be diagnosed by your veterinarian detecting a murmur and sometimes hearing fluid in the lungs by listening with a stethoscope.
Additional diagnostics can be performed to better determine the severity of your dog’s condition. Chest X-rays are used to determine the size and shape of the heart and the presence of fluid in the lungs. An ECG (electrocardiogram) measures the electrical activity of the heart and provides an accurate determination of both heart rate and rhythm. Any abnormal rhythms can be detected and evaluated.
Ultrasound examination utilizes sound waves to evaluate the heart’s contractions and to measure the heart’s muscle thickness and the amount of blood pumped by the heart.
Dilated cardiomyopathy is a degeneration of the heart muscle. As a result of this degeneration, the muscle becomes thinner. The pressure of the blood inside the heart causes the thin walls to stretch resulting in a much larger heart. Again, this condition is more common in large breed dogs. They may have a very sudden onset of clinical signs. Some dogs may develop severe heart failure in only a few hours. Rapid, heavy breathing, a blue tongue, excessive drooling or collapse may be the first signs. Dilated cardiomyopathy is a very serious disease that must be accurately diagnosed and aggressively treated. Some dogs do well with treatment; however, some dogs will never resume a normal lifestyle even with proper treatment.
Treatment of heart diseases in dogs will usually require treatment for the rest of their lives. Treatment is tailored according to each patient’s needs. Many of the medications and follow-up tests are relatively inexpensive and effective. Some medications are more expensive, but are more effective at improving quality of life. Diuretics are medicines used to remove excess fluid from the body. Angiotensin converting enzyme (ACE) inhibitors are medicines used to lower blood pressure allowing the heart to pump easier.
Digoxin is a medicine used to actually help the heart contract more effectively. With correct treatment, many dogs are able to live a normal life for many months to years.
Early detection makes treatment much more effective. If your pet shows any symptoms of heart disease, contact your veterinarian as soon as possible to ensure your pet lives a long, healthy and happy life!