Cardiomyopathy and the Doberman

There is a disease in some Doberman Pinschers that can be undetected until too late called Occult Cardiomyopathy. Let’s learn a bit about it.

Occult cardiomyopathy (OC) is a slowly progressive heart muscle
disease that results in abnormal heart rhythms (arrhythmias)
in Doberman Pinschers. The type of arrhythmias it causes are often ventricular premature contractions (VPCs) and ventricular tachycardia (VT). It is also called arrhythmogenic cardiomyopathy .

Dobermans with OC may have no clinical signs for long periods, which is why the disease is referred to as occult or silent. Eventually the dog develops arrhythmias and, later, dilated cardiomyopathy. OC runs in certain lines of Dobermans, so a genetic factor is involved. It can be traced back to the original seven sires of Doberman lines in the United States, three of which died suddenly when they were middle-aged.

OC can start as early as 9-12 months of age, but most dogs are between 2-4 years old. By 6 years of age, about 50% of Dobermans have OC. Most dogs with OC have no symptoms. Their arrhythmias may be detected on a routine physical examination or on a screening electrocardiogram (ECG) or Holter monitor study. Dogs with more frequent VPCs or VT may have fainting episodes
(syncope), or they seem to pass out for short periods of time (like seconds) and then come back. About 30% of affected dogs die suddenly, without prior symptoms. Some dogs will show tiring with minimal exertion as well.

Since OC is very prevalent in Dobermans, annual screening of adult dogs often starts at 2-3 years of age, and may include a 24-hour Holter monitor and echocardiogram (heart ultrasound) study. The likelihood of finding VPCs, VT, or echocardiographic changes increases as the dog ages. Once arrhythmias have been found, the only way to diagnose OC is to rule out all other causes of ventricular arrhythmias.

How do you treat this? In some cases, hospitalization is needed to stabilize these dogs, depending on test result or clinical signs. Some can be treated as an outpatient with frequent rechecks early in the course of medications. Unfortunately, the more severe the arrhythmia, the greater the chance of sudden death. Not every drug works in every dog, so sometimes a dog must be switched from one drug to another to control the ventricular arrhythmias. Side effects can occur, so communication with your vet is needed to best administer the proper care.

Affected Dobermans require frequent ECGs until their VT or VPCs are controlled. Ideally, a Holter monitor is applied to dogs with non–life-threatening arrhythmias to document the frequency of the arrhythmias prior to treatment. Another Holter recording is done after the drug has reached adequate blood levels, to judge
how effective it is in controlling the abnormal beats. Affected dogs require antiarrhythmic therapy for the rest of their lives. Echocardiograms may be done every 6-12 months to monitor for evidence of dilated cardiomyopathy, which can follow OC. Dobermans with infrequent VPCs that are feeling well usually develop changes on their echocardiograms within 1 year. Within 2 years, their VPCs and heart changes often get worse, and 30-50% of these dogs may die suddenly.

Dobermans with severe VPCs or VT that are well controlled with medication can live up to 1 year or longer. No drug is 100% effective in preventing sudden death. The better the arrhythmia is controlled, the less likely it is that sudden death will occur. Holter monitors provide the best way to evaluate how well the medications are controlling the arrhythmias.

If dilated cardiomyopathy develops, the dog’s life span is only weeks to months (average, 3-4 months). Because OC has a genetic basis and runs in families, it is wise not to breed dogs that have the problem.

This is a problem widely seen in Dobermans so do your research when you get a puppy and ask the breeder about this and whether they follow up their puppies into adulthood to see if any show this. See how old their dogs are in the kennel, as that can give you an idea of whether the dogs can live past a certain age, as not always are folks forthcoming about this; many reputable breeders are keenly aware of this and make every effort to select the parents that don’t show this in their puppies or have lines of dogs that are free of OC. It is a bummer of a disease.

Some lines of dogs in the USA and elsewhere stem from a very narrow band of dogs or just a few dogs, and over time, in-breeding or very close line breeding will lead to the exhibiting of poor genetic traits, such as OC or in King Cavalier, mitral valve disease.

Ref; Rebecca E. Gompf, DVM, MS, DACVIM