Heart Disease in Pets
Does your pet have characteristic symptoms of heart disease such as shortness of breath, coughing or exercise intolerance? Has your veterinarian heard an abnormal sound when listening to your pet’s heart? If so, your beloved pet may suffer from one of many different types of heart disease.
In some cases, heart disease may require no treatment and never impact your pet’s quality of life. In other cases, symptoms of heart disease may require intensive medical therapy and may even shorten the pet’s lifespan. It is important to know how the heart works and what type of heart disease is present so your pet may be appropriately treated.
The heart is responsible for delivering blood that is rich in oxygen from the lungs to all the tissues and organs of the body. The upper chambers of the heart, known as the right and left atria, receive blood in large vessels coming from the body and lungs. The lower chambers of the heart, the ventricles, are composed of thick, muscular tissues that pump the blood out of the heart. The left side of the heart delivers blood to the body; the right side of the heart sends it to the lungs, where it picks up oxygen. There are valves between the ventricles and atria as well as between the ventricles and large blood vessels that exit the heart. These valves prevent the blood from moving backward through the heart. Some of the cells in the heart are able to generate electrical signals that cause the rhythmic beating of the heart.
When the heart doesn’t function properly, it may be because of one of the following types of heart diseases:
Congenital Heart Disease
Congenital heart disease means that the problem in the heart has been present since birth. Animals suffering from congenital heart disease tend to be diagnosed at a younger age than animals with other kinds of heart disease. In some cases, though, the disease may not be discovered until much later in life when symptoms develop. Your veterinarian may suspect a congenital heart defect if abnormal heart sounds are noted in a young animal or if symptoms of heart failure (difficulty breathing, coughing, fainting) develop early in an animal’s life. Chest X-rays, listening to the heart through a stethoscope and looking at the heart with ultrasound will help your veterinarian determine the underlying cause and the best treatment. Some congenital heart defects can be managed with medicine or surgery.
Acquired Heart Disease
Acquired heart disease refers to conditions that develop later in life. This group may be further divided into several categories.
Valvular disease: Most common in older, smaller-breed dogs, valvular disease means that the valves within the heart are no longer functioning. Imagine the valves as doors; valvular disease is when the doors don’t close properly. When heart valves malfunction, often an abnormal heart sound or murmur develops. Some of the pets in this group will never develop any problems as a result of their heart disease. For other pets, when the heart is no longer able to compensate for faulty valves, fluid backs up into the lungs, leading to exercise intolerance and coughing. Medication known as diuretics can help pull fluid out of the lungs. Other drugs help improve the ability of the heart to pump effectively. Many pets do well taking oral medication for a long time, even after their hearts have started to fail from valvular disease.
Myopathies: This group refers to diseases of the muscle of the heart. While these conditions can occasionally cause a heart murmur, often they are silent until signs of heart failure develop (cough, abnormal fluid build-up). Cats and larger-breed dogs often suffer from this type of heart condition.
When the ability of the heart to pump blood is compromised due to a diseased heart muscle, fluid may build up in abnormal sites in the body. When the left side of the heart fails, fluid builds up in the lungs and may be treated with medication. When the right side of the heart fails, fluid may accumulate in the abdomen. While medication may reduce the amount of fluid, most cases of right-side heart failure will require the fluid to be periodically removed with a needle and syringe. Veterinarians often prescribe pills that improve the heart’s ability to pump.
Other types of myopathies frequently lead to electrical problems in the heart, as detailed below.
Electrical abnormalities: The regular beating of the heart is vital for proper functioning of the heart. When there are electrical problems in the heart, an irregular heartbeat known as an arrhythmia develops. Significant arrhythmias may lead to serious symptoms. The electrical system of the heart is evaluated with an electrocardiogram (EKG).
Treatment of an arrhythmia depends on which type develops. Oral medications given at home may treat some of the common abnormal rhythms. Other rhythms may be treatable with an implantable device known as a pacemaker. Pacemakers are usually only available at referral centers.
Infectious disease: Several types of infections can lead to heart disease. In Texas, veterinarians commonly diagnose heartworm disease in dogs that are not on regular heartworm prevention medications. Another infectious disease diagnosed frequently in Texas is Chagas disease, which is caused by a parasite that attacks the heart muscle. Insect vectors transmit both of these parasitic diseases. For example, mosquitoes pass on heartworms, while “kissing” or “assassin” bugs carry Chagas disease.
Heartworm disease is treatable in dogs (but not cats) with a series of injections, along with a monthly heartworm preventive medication. Veterinarians treat pets with Chagas by managing the heart disease symptoms; the actual parasitic infection may be prevented but not cured once it is acquired.
With recent advances in veterinary cardiology, many pets with heart disease may be cured or managed very effectively with medication. The first step is identifying which type of heart disease your pet has and then speaking with your veterinarian about the prognosis and treatment options.
Suzanne Brown, DVM, is a graduate of Texas A&M College of Veterinary Medicine who lives in Belton, Texas. Dr. Brown practices at Belton Small Animal Clinic and Central Texas Mobile Veterinary Ultrasound.