Doberman Cardiomyopathy

Disease progression

In most cases the disease starts with ventricular premature complexes (VPCs or VES). During this occult phase, echocardiography may still look normal or only mildly abnormal.

Some affected Dobermans die suddenly already during this phase, usually because of severe ventricular arrhythmias.

If the disease progresses further, the heart later develops left ventricular systolic dysfunction, chamber enlargement and frequently signs of left-sided congestive heart failure, especially pulmonary edema.

How common is the disease?

Doberman cardiomyopathy is very common in Europe. In a study from our group, the prevalence was about 58.7%. This means that a large proportion of Dobermans develop the disease during their lifetime.

Risk increases substantially with age.

These numbers underline why regular cardiac screening is so important in this breed.

What causes Doberman cardiomyopathy?

The disease is considered very likely to be genetically determined. In Dobermans, a classic nutritional deficiency such as may occasionally contribute to DCM in some other breeds usually does not play a major primary role.

The condition is regarded as inherited. That is why both early detection and responsible breeding screening are important.

Which symptoms can occur?

Dogs in the occult phase often have no obvious symptoms. Even so, dangerous arrhythmias may already be present.

In the symptomatic phase, signs may include:

• cough
• reduced exercise tolerance
• decreased activity and stamina
• increased resting respiratory rate
• shortness of breath
• syncope
• arrhythmias
• sometimes ascites or right-sided heart failure
• sudden cardiac death

Does hypothyroidism cause DCM?

Based on current scientific evidence, there is no proven causal relationship between hypothyroidism and classic Doberman cardiomyopathy.

Thyroid hormone treatment should therefore only be used when true hypothyroidism has been clearly diagnosed.

Screening examinations

Because the disease is so common, we generally recommend regular cardiology screening in clinically healthy Dobermans from about 2 to 3 years of age, usually once yearly.

Depending on age, family history, breeding plans and previous findings, shorter intervals may also be appropriate.

Holter monitor or 24-hour ECG

Holter monitoring is a central part of early detection in the Doberman. It records the heart rhythm continuously over 24 hours or longer while the dog is in its normal home environment.

It is especially important during the occult phase because many affected dogs first develop ventricular arrhythmias before showing obvious clinical signs.

Based on our data, more than 50 VES/VPCs in 24 hours is considered abnormal in Dobermans. Because occasional ectopy may also occur for other reasons, repeated recordings are often used to confirm the diagnosis.

Short ECG

A routine ECG records only a short time period and is therefore not sufficient by itself for early screening.

However, if even a single ventricular premature complex is seen during a short ECG or during echocardiography, a Holter examination is usually indicated.

Echocardiography

With echocardiography we assess heart size and pump function. Moderate and severe abnormalities are often relatively easy to identify, while mild early changes are more difficult.

In Dobermans, studies from our group established important reference values and evaluated modern methods for earlier detection. In particular, the Simpson method can help detect early chamber enlargement and systolic dysfunction sooner than M-mode alone.

Radiographs

Thoracic radiographs are less sensitive for early detection, but they can provide very important information when dogs already have symptoms such as cough or breathing difficulty.

They are especially useful to detect pulmonary edema, left atrial enlargement or other signs of congestion.

Troponin I

Cardiac troponin I (cTnI) is released when heart muscle cells are damaged. Studies from our group showed that cTnI may already be increased in some Dobermans before later abnormalities become evident on Holter recordings or echocardiography.

NT-proBNP

NT-proBNP is a marker of cardiac stress. It can be elevated in dogs with heart failure and also helps distinguish cardiac from non-cardiac causes of dyspnea.

It can also be useful as an additional screening test in occult Doberman cardiomyopathy.

Video about the disease

Here you can find a video about Doberman cardiomyopathy with detailed information and interview.

Treatment of ventricular arrhythmias

Treatment of arrhythmias is especially important when sustained ventricular tachyarrhythmias, syncope or other markers of increased rhythm risk are present.

Main goals of therapy include:

• reducing the risk of sudden cardiac death
• preventing ventricular tachyarrhythmias
• substantially reducing the number of VES/VPCs
• improving clinical signs

Treatment of chronic heart failure

When chronic congestive heart failure is present, treatment usually includes several components:

• diuretics such as furosemide or torasemide
• pimobendan
• ACE inhibitors
• when needed digoxin, especially in atrial fibrillation
• control and treatment of arrhythmias
• in refractory cases additional diuretics such as thiazides or spironolactone

Treatment is always individualized based on findings, symptoms and the rhythm status of the patient.

Treatment of acute heart failure

In acute congestive heart failure, furosemide is one of the most important emergency drugs. Depending on the individual case, additional intensive care measures may be necessary, including intravenous positive inotropes such as pimobendan or dobutamine.