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listen to your heart, part 1: dilated cardiomyopathy

  • Dr. Kim
  • Posted by Dr. Kim Smyth on
    Staff Veterinarian and Pet Health Writer of Petplan

Heart disease in dogs and cats is quite common, but the old veterinary saying holds true—cats are not small dogs! When you break down the word “cardiomyopathy,” you’ll find that it means “disorder of the heart muscle.” Through the next two blogs, we’ll cover cardiomyopathy in dogs and cats, how their heart muscles are affected differently, and what similarities they share.


Let’s start with dogs.


When dogs have cardiomyopathy, their enlarged heart is typically due to a condition called dilated cardiomyopathy (DCM), which is a dilation of the chambers of the heart. Because the condition is so prevalent in several breeds, there is surely a genetic component to the disease, but nutritional and infectious causes have also been suggested.


When a dog suffers from DCM, the muscles of the lower chambers of the heart thin out and dilate, reducing the contracting ability of the heart. When the heart doesn’t contract effectively, blood cannot be pumped through the body as it should, making for a buildup upstream from the affected chamber(s).


Clinical signs of DCM can be the result of oxygenated blood not reaching the tissues of the body, or they can be due to the back up of blood upstream from the heart. In the former case, weakness, decreased appetite, lethargy, collapse and fainting can be seen. In the latter case, fluid builds up in the lung tissue (pulmonary edema) as well as in the chest space around the lungs (pulmonary effusion). This kind of fluid buildup is common when the left side of the heart is affected, and causes clinical signs like coughing and respiratory distress. When the right side of the heart is affected, fluid builds up in the abdomen and is called ascites.


Over time, the stresses on the heart can predispose a patient with DCM to the development of cardiac arrhythmias. In some cases, sudden death will occur because of cardiac arrhythmias.


Large and giant breed dogs are more prone to develop DCM than their smaller cousins, but small dogs aren’t immune. Specific breeds with known predilections to DCM include:


  • Doberman Pinschers
  • Great Danes
  • Boxers
  • Newfoundlands
  • Dalmatians
  • Portuguese Water Dogs
  • Cocker Spaniels


Your vet may suspect DCM in your dog if he has clinical signs like those described above, especially if his breed fits the bill. A radiograph (x-ray) of the chest may show an enlarged heart and changes in and around the lungs, but an echocardiogram will show the dilated heart chambers while an electrocardiogram will pick up on cardiac arrhythmias.


Sometimes, your dog will be asked to wear a Holter monitor, which is a 24-hour electrocardiogram. Your veterinarian may want to refer your pet for an initial consult with a cardiologist, but it is likely that your pet’s case can be managed mostly by your vet with periodic rechecks with the cardiologist as needed.


There is no one specific treatment for DCM. The goal of therapy is to try to help the heart pump more efficiently, manage fluid accumulation in the lungs or abdomen and correct cardiac arrhythmias. Oral medications will be prescribed by your pet’s cardiologist or your regular veterinarian.


The prognosis for pets with DCM varies widely, depending on the severity and progression of disease, as well as whether your pet presents in congestive heart failure. Subtle changes in a dog’s behavior may send an owner looking for answers before congestive heart failure develops, but often, symptoms of the disease are not obvious. In some heartbreaking cases, sudden death occurs even before a single symptom is shown.


Lethargy and decreased appetite are common complaints, and can occur for many reasons. But when these symptoms are prolonged or accompanied by other things like fainting, pale gums, and coughing, put a visit to the vet on the top of your ‘to do’ list!

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