Juvenile dilated cardiomyopathy, or puppy heart disease, is a genetically inherited defect in the muscles of the heart. In adult-onset dilated cardiomyopathy, the chambers of the heart increase, causing the muscles of the heart wall to thin, eventually leading to congestive heart failure. The majority of cases are idiopathic, with no known cause. Unfortunately, the prognosis for puppy heart disease is not good; many who acquire it pass away a few weeks after diagnosis.
When it comes to adult-onset dilated cardiomyopathy, the average age of onset is 4 to 10 years. Large and giant dog breeds are at a greater risk. Some of these breeds include Afghan hounds, boxers, cocker spaniels, Dalmatians, Doberman pinschers, great Danes, Newfoundlands, old English sheepdogs, Portuguese water dogs, Scottish deerhounds and Saint Bernards. Symptoms of juvenile dilated cardiomyopathy present between 10 days of age and 7 months, with congestive heart failure following within a few weeks. Symptoms do not always present but can include anorexia, lethargy, vomiting, difficulty breathing and fluctuating heartbeat. Breeds showing genetic predisposition to juvenile dilated cardiomyopathy include Portuguese water dogs and Doberman pinschers.
Portuguese Water Dog Study
A 2002 study published in the Journal of Veterinary Internal Medicine looked at the occurrence and detection of juvenile dilated cardiomyopathy in Portuguese water dogs. Looking at 124 puppies, researchers found no clinical differences in blood concentrations, serum chemicals, electorcardiograms or urine metabolites between affected and unaffected puppies. Only echocardiography enabled researchers to diagnose the condition before clinical signs appeared. In the 10 puppies diagnosed, acute congestive heart failure followed within one to four weeks of diagnosis.
Doberman Pinscher Study
A 2003 study published in the Journal of Veterinary Cardiology looked at the occurrence of dilated cardiomyopathy in juvenile Doberman pinschers. Researchers looked at seven puppies referred for cardiovascular examinations. Six of these puppies were from a litter of eight; the other two from the litter had already died from congestive heart failure. In the six from the litter, three were euthanized at 4 weeks of age with advanced dilated cardiomyopathy; one was diagnosed at 11 weeks of age and lived to two and a half years. The other two puppies were unaffected and lived into adulthood.
Given that juvenile dilated cardiomyopathy is genetic, you may wonder how, in the Doberman study with puppies from the same litter, some were unaffected. This happens based on the parents' genetic makeups. Generally, if one parent is a carrier of the trait while the other is not, half of the puppies will tend to be carriers while the others are clear. If one parent has juvenile dilated cardiomyopathy while the other is clear, all puppies will be carriers. If both parents are carriers, 25 percent of the puppies will be clear, 25 percent will have the condition and 50 percent will be carriers, on average. The only way an entire litter of puppies is likely to all have juvenile dilated cardiomyopathy is if both parents are affected. Given the high mortality rate, this is not common. In breeds prone to this condition, it is a good idea to consult with the breeder and ask for any evidence of juvenile dilated cardiomyopathy in the puppy’s family history. Dogs with the gene should not be bred.