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DILATED CARDIOMYOPATHY

 

About the Diagnosis


Cause: The heart is an organ made of muscle cells. When the heart contracts, it pumps oxygenated blood to the body and at the same time it sends "used" unoxygenated blood to the lungs to pick up oxygen. Within the heart are four chambers and four valves. These one-way valves ensure that blood always flows in the correct direction.
Dilated cardiomyopathy is a reduced ability of the heart to contract that leads to decreased pumping of blood forward throughout the body. The problem is an inherent weakness of the heart muscle tissue, which occurs as a result of genetics (usually) or nutritional deficiencies (rarely). With dilated cardiomyopathy, the circulation is disrupted in such a way that fluid weeps through the walls of the blood vessels and accumulates in the lung tissue (pulmonary edema) or leaks into body cavities such as the abdomen (ascites) and chest cavity (pleural effusion).

Dilated cardiomyopathy is often a serious, life-threatening disease, but it has many degrees of severity. Some patients diagnosed early respond well to treatment and live comfortably for months or sometimes years, whereas in other, more serious cases, dilated cardiomyopathy is the cause of death within days or weeks of diagnosis. The way to determine the severity of the case is to perform a series of cardiac tests (see below), and even then, the ability to predict life span is never exact.

This disease is rarely diagnosed in small dogs or cats; however, it is a common cause of heart disease in large and giant breed dogs that are middle- to older-aged. The cause is often unknown but is thought to be genetic in some breeds. Unfortunately, dilated cardiomyopathy may be present without symptoms (see Signs to Watch For) and may deteriorate quickly once symptoms occur. The onset of symptoms can be sudden and severe.

Diagnosis: The symptoms of dilated cardiomyopathy are often subtle at first and/or not specific (i.e., they look like symptoms of other, entirely different diseases). Therefore, your veterinarian will begin by performing a thorough physical exam and taking a complete history from you, including asking questions about the nature and duration of symptoms you observed, any current medications, previous medical problems, and so on. Chest x-rays are necessary; they show the size of the heart, may show fluid accumulation in the lungs or chest cavity if present, and can help to identify the presence or absence of other reasons for breathing problems. An electrocardiogram (EKG) depicts the pattern of electrical activity in the heart and is important in dilated cardiomyopathy because the heartbeat is sometimes severely erratic (requiring specific types of medications) as a result of this disease. Blood work, including a complete blood count (CBC) and serum chemistry profile, and a urinalysis can help to determine if other organs are affected and to pinpoint risk factors that would influence the choice of medications for treatment.

The confirmatory test for dilated cardiomyopathy is an echocardiogram, commonly called a cardiac ultrasound. This test shows the internal architecture of the heart including the function of the different heart chambers, thickness of the walls, condition of the heart valves, and direction and speed of blood flow, all of which are important points in assessing patients suspected of having (or known to have) dilated cardiomyopathy.

Living with the Diagnosis

Give all medications as directed by your veterinarian. Talk to your veterinarian about the possible side effects of the medications so that you know what is normal and abnormal. During the course of treatment, one or more of the tests mentioned above will often be repeated to ensure that the drugs are working safely and effectively.
When the pumping action of a heart with dilated cardiomyopathy is severely compromised, then congestive heart failure may occur. See Congestive Heart Failure.

Follow instructions to restrict your dog's activity level. Too much exercise or play in a patient with dilated cardiomyopathy can exacerbate this condition.

Feed only recommended diets. Some treats have a high sodium content and should be avoided. Be sure to discuss treats that are permitted with your veterinarian.

Occasionally, dilated cardiomyopathy is caused by a deficiency of taurine, a type of amino acid normally found in food. Many breeds of dogs have taurine deficiency associated with their dilated cardiomyopathy, and it is important to identify this deficiency (with a blood test) because adding taurine to the food can help stabilize or even reverse the dilated cardiomyopathy process.

Treatment

Treatment depends on the stage of the disease and your pet's overall health. If symptoms are severe, your dog may be hospitalized while medications and oxygen supplementation are given. Your dog may need a sedative to promote relaxation. Stress and anxiety can make breathing more difficult. In these more serious cases with severe respiratory distress (very labored breathing), the tests described above may be withheld and treatment begun only once your dog is more comfortable.

The cornerstones of treatment for dilated cardiomyopathy are specific medications. Diuretics remove fluid that has accumulated in the abdomen or lungs and can cause your dog to drink more water and urinate more. An angiotensin-converting enzyme inhibitor (ACEI) helps to relax blood vessels to allow more efficient blood flow from the heart and ease the workload on the heart. In some cases where fluid has accumulated around the lungs and is compressing or collapsing the lungs, a needle may need to be used for withdrawing the fluid from the chest cavity and allowing the lungs to re-expand. Not all of these medications may be necessary, and others are available. The treatment is tailored to the patient's exact situation and therefore is almost never the same from one case to another.

DOs

• Go to your veterinarian or the local emergency clinic immediately if your dog develops breathing problems or losesconsciousness.

• Inform your veterinarian if your dog has ever been diagnosed with a medical condition and is taking medication.

• Give medication exactly as directed by your veterinarian and if you are concerned about possible negative effects, discuss them with your veterinarian immediately rather than simply discontinuing the treatment.

• Realize that dilated cardiomyopathy is often an irreversible disease that is of genetic origin and that medications can make patients with dilated cardiomyopathy comfortable, happy, and active, but rarely athletic.

• Realize also that many individual dogs do not understand the limitations of their heart condition and may wish to be more active than they should given their heart's compromised state. Finding the right balance between cardiac risk (from physical activity) and enough activity to bring a dog satisfaction and happiness should be discussed with your veterinarian.

DON'Ts

• Do not postpone visiting your veterinarian if you observe any symptoms of dilated cardiomyopathy. Prompt diagnosis and treatment may improve your dog's quality of life.

• Do not give medication that you have at home that has been prescribed for human use; some of these may interfere with treatment and cause even more severe problems.

• Do not assume that your dog with dilated cardiomyopathy knows when to withhold its physical exertion level.

When to Call Your Veterinarian

• If you cannot keep a scheduled appointment.

• If you are unable to give medication as directed.

Signs to Watch For

• Watch for general signs of illness, which include vomiting, diarrhea, changes in appetite and weight, and changes in behavior such as hiding more than usual and aggressiveness.

• Watch for signs of dilated cardiomyopathy, which include weakness, lethargy, coughing, exercise intolerance, and fainting.

Routine Follow-Up

• Because this is a progressive disease, follow-up appointments are necessary to monitor progress, to determine if treatment should be adjusted, and to pursue any abnormalities on previous blood tests.