Dilated Cardiomyopathy (DCM) of Dogs
Dilated cardiomyopathy (DCM) is a disease of the heart muscle that causes it to weaken and enlarge. Because of these changes, the heart becomes unable to pump blood effectively, which often leads to congestive heart failure.
Which dogs get DCM? Why do they get it?
This disease is most commonly seen in middle-aged or older large-breed dogs such as Doberman Pinchers, Boxers and Great Danes. On occasion, it is also diagnosed in Cocker Spaniels. There are strong genetic tendencies in these breeds to develop this disease. Genetic tests for DCM in certain breeds are currently being studied and are likely to be available in the near future.
In a few rare cases, other causes are identified. Nutritional deficiencies of the amino acid taurine have been implicated in the development of this disease in a few breeds. A commonly used chemotherapeutic drug called doxorubicin has also been linked to the development of DCM. Although uncommon, infections by certain viral (parvovirus) and parasitic (Chagas disease) agents are known to lead to DCM or DCM-like changes in the heart.
What are the signs of DCM?
DCM commonly manifests in one of three ways:
- Left heart failure: When the heart can no longer pump blood effectively throughout the body, pressures in the left side of the heart build up, leading to the development of fluid in the lungs. These dogs exhibit difficulty breathing, exercise intolerance or coughing.
- Right heart failure: In some cases, the right side of the heart fails, leading to a build-up of fluid within the abdomen and occasionally in the space surrounding the lungs in the chest called the pleural space. These dogs may be seen for exercise intolerance, an enlarged abdomen or difficulty breathing.
- Arrhythmias: As DCM progresses, many affected dogs experience problems in the electrical part of the heart that signals when and how the heart should beat. If signals to the rest of the heart are abnormal, an arrhythmia, or an abnormal heart rhythm, occurs. This may be noted on a routine examination when your veterinarian listens to your dog’s heart with a stethoscope. Severe arrhythmias may result in dogs suddenly collapsing or fainting. Some dogs that experience arrhythmias due to DCM will die suddenly with no other previous symptoms of disease.
What is the treatment for DCM?
Because transplants are not feasible for affected dogs at this time, current therapies are limited to treating the clinical signs the dogs experience. Drugs called diuretics, or “water pills,” such as furosemide can help remove the fluid build-up in the lungs. The extra fluid is pulled from the lungs into the blood vessels, where it can be filtered out by the kidneys and eliminated from the body as urine. Physically removing fluid that has developed in the abdomen or around the lungs can also be performed on an outpatient basis, which is performed by inserting a small needle into the pocket of fluid and using a syringe to suction it out of the body. Often, a drug called pimobendan is prescribed to help improve the heart’s remaining ability to pump blood. Medications can also be used to treat arrhythmias.
How is DCM diagnosed?
The definitive diagnosis of DCM is made with an echocardiogram, or ultrasound of the heart. The diagnosis is based on the thickness of the heart muscle and the strength of the heart’s contraction in comparison to other dogs of the same breed.
Many clinical signs may lead your veterinarian to presumptively diagnose DCM. The presence of certain arrhythmias on an electrocardiogram (ECG), especially in an at-risk breed, is a red flag for the presence of DCM. X-rays of the heart may show an enlarged heart. However, the disease can still be present even if the heart does not appear to be enlarged. The presence of right or left heart failure in an adult large-breed dog, which may be diagnosed with a physical exam and/or X-rays, will put DCM high on the list of possible causes.
Can I prevent DCM?
Genetic tests, currently under development, will someday allow selective breeding to minimize the occurrence of this disease. Except for the rare cases caused by a taurine deficiency, nutritional supplements have not been shown to affect the course of the disease. Administering medications prescribed by your veterinarian can reduce the clinical signs, making a dog more comfortable and prolonging your pet’s lifespan.
What is the prognosis for DCM?
Ultimately, DCM is a progressive, incurable and eventually terminal disease. However, with appropriate medical intervention, the affected animal may enjoy many months or years of good quality life.
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.