By Maribeth Hartwick, DVM
WHAT IS DILATED CARDIOMYOPATHY (DCM)?
DCM is one of the most common acquired heart diseases in dogs. It is a disease of the heart muscle (myocardium), in which the muscles of the lower pumping chambers (ventricles) lose its ability to contract normally. This occurs because the heart muscle becomes thin and stretched, much like a balloon. DCM most commonly affects the left side of the heart (the side that receives blood from the lungs and pumps it to the body), but can also affect the right side of the heart (which receives blood from the body and pumps it out to the lungs). In either case, blood ineffectively pumped by the heart "backs up." The heart, in order to compensate for extra blood volume, enlarges. Congestive heart failure (CHF) is a result of an enlarged heart that does not contract/pump blood effectively. In left sided CHF, fluid "backs up" within the lungs (pulmonary edema). In right sided CHF, fluid accumulates around the lungs (pleural effusion) and in the abdominal cavity (ascites).
WHAT ARE THE SYMPTOMS OF DCM?
Symptoms depend on the breed of dog, stage of disease and which side of the heart is affected. Early in the course of the disease, affected individuals may look normal. Only when dogs show signs of heart failure do most owners seek a Veterinarian's attention. Common signs are: loss of appetite, pale gums, difficulty breathing, cough, increased heart rate, periods of weakness, fainting and distended abdomen (ascites). Some breeds (especially boxers) can exhibit sudden fainting or even death due to heart arrhythmia (abnormal heart rhythm) even before signs of CHF occur.
WHAT BREEDS ARE MORE COMMONLY AFFECTED BY DCM?
There are several dog breeds that are predisposed to DCM. These include: Doberman Pinscher (#1 breed), Great Danes, Boxers, Newfoundlands, Portuguese Water Dogs, Dalmatians and American Cocker Spaniels. Also affected are the Airedale Terrier, Golden Retriever, Irish Wolfhound, Saint Bernard, Scottish Deerhound and Standard Poodle. Other breeds are affected less commonly. Mostly large and giant breeds are affected although DCM can occur in smaller breeds and cats as well. More male dogs are affected than females.
WHAT CAUSES DILATED CARDIOMYOPATHY?
A genetic tendency is suspected in many breeds. Although there are no current genetic tests available to identify the genes and affected individuals, research is ongoing. In addition to inherited tendencies, there may be other factors that contribute. These include: Nutritional deficiencies - Taurine (American Cocker Spaniels, Newfoundlands, cats); Carnitine (Some Boxers, Doberman Pinschers); Toxic drugs - Such as chemotherapy (Doxorubicin/Adriamycen); Some infectious viruses.
HOW DO I KNOW IF MY PET HAS DCM? HOW IS IT DIAGNOSED?
Many pets may not show symptoms in the early stages of disease, therefore diagnosis can be complicated. The first step is a thorough physical/cardiac exam. A physical exam once or twice yearly, prior to any anesthetic procedures, or as recommended by your veterinarian is suggested in high-risk individuals. Tests depend on the dog breed and whether or not they are currently showing symptoms. Your veterinarian may suggest one or more of the following tests. An Electrocardiogram (ECG) assesses the heart's rate and rhythm, and can indicate changes in heart size; An Echocardiogram (ultrasound of the heart) allows for an internal moving view of the heart's function and structure; a Holter Monitor (24-hour ECG) is a device worn for 24 hours that picks up irregular heartbeats that may only occur periodically in 24 hours (especially in Boxers); a Chest X-Ray; Bloodwork (CBC/Chemistry Panel) evaluates metabolism/ electrolytes to screen for Nutritional Deficiencies (Taurine/ Carnitine Blood levels) (especially in Boxers, American Cocker Spaniels, Doberman Pinscher).
If diagnosed early, treated and monitored, patients may live for several years before developing clinical signs. Treatments are geared towards combination medical therapies to improve the heart's ability to contract, improve blood flow, control fluid overload, treat symptoms of heart failure and improve overall quality of life.
Please call today to schedule an appointment with one of our doctors for a comprehensive cardiac exam and to answer any further questions you may have.