Dilated cardiomyopathy (DCM) is an adult-onset heart disease seen most often in large to giant breed dogs. It is particularly common in the Doberman pinscher, but can also be seen in medium size dogs, such as the cocker spaniel. DCM is characterized by dilated heart chambers, a thin heart muscle, and decreased contractility (ability of the heart muscle to contract). Decreased contractility results in a decrease in the heart’s ability to pump blood throughout the body (systolic dysfunction).
Although clinical presentation may be similar to DCM, systolic dysfunction is not always a result of DCM. Systolic dysfunction can also develop secondary to a taurine deficiency, myocarditis (inflammation or infection of the heart muscle) and other causes that we cannot definitively test for (e.g. viruses).
Dilated cardiomyopathy often causes only subtle, if any, physical changes. If present, heart murmurs, caused by turbulent blood flow as blood leaks backwards across the affected valve, are often quiet. Other abnormal heart sounds, such as a gallop sound, or an arrhythmia (abnormal heart rhythm) may be identified during a physical exam. Thoracic radiographs often do not show significant enlargement of the heart in the early stages of DCM.
The best way to diagnose DCM is by referral to a cardiologist for an echocardiogram (ultrasound of the heart) to evaluate for specific heart chamber enlargement and to evaluate heart function. A Holter monitor (24-hour ECG) is recommended to evaluate arrhythmias, which can be associated with DCM. Other diagnostics, such as blood pressure or blood work may be recommended to further evaluate for other concurrent diseases or factors that may complicate management of DCM. If systolic dysfunction is present in a breed not typically known for DCM, tests such as taurine levels, thyroid levels and infectious disease screening may be recommended.
Complications and Sequelae
Over time, signs of heart failure may develop. These signs include cough, difficulty breathing, increased respiratory rate, weakness, lethargy, exercise intolerance and collapse. Less commonly, abdominal distension from fluid build-up in the abdomen may occur. In addition, arrhythmias may develop or worsen, and lead to signs of weakness, lethargy and collapse. These arrhythmias may also increase the risk of sudden death.
Pulmonary hypertension (PH), or high blood pressure in the lungs, may develop. If the PH is severe enough to result in more pronounced clinical signs, including exercise intolerance and collapse, medications can be added to the treatment protocol.
In the asymptomatic stages of DCM, the best way to monitor DCM is with periodic echocardiograms and/or thoracic radiographs. Treatment with an ACE inhibitor +/- spironolactone is recommended to help prevent fluid retention and fibrosis (scarring) of the heart muscle and to control certain hormones that are elevated with heart disease.
Avoid feeding your pet high sodium diets or treats, like bacon, pig ears, sausage, etc. It is best to maintain your pet on a moderately sodium restricted diet, such as any senior or kidney diet.
As the disease progresses, other medications may be necessary. Anti-arrhythmic medications may be recommended if arrhythmias are severe. Additional medications used to treat heart failure include diuretics to help remove extra fluid from the body; pimobendan to help improve heart function; and medications to treat pulmonary hypertension.
It is not uncommon for dogs with heart disease to be exercise intolerant, particularly in hot summer months, so allow your pet to set his or her own pace.
In general, DCM carries a guarded prognosis because it is a progressive disease that can be managed with medication but cannot be cured. Early, or occult, dilated cardiomyopathy represents the earliest diagnosable stage of DCM. In general, we expect occult DCM to progress slowly, and the progression to severe heart failure can potentially be delayed by initiation of appropriate medication. Unfortunately, even with medication, patients will develop signs of heart failure in 1-2 years. The average life span after diagnosis of heart failure (fluid in the lungs or abdomen), with appropriate treatment, is months to a year. Frequent monitoring is important in maximizing treatment of heart failure. Our goal is to help your pet feel as good as possible, for as long as possible.
For more information on this disease, speak to the veterinarian who is treating your pet.