Laura Bay-Williams, B.S., D.V.M.

Cardiomyopathy means enlargement or thickening of the heart.  There are 3 different types:  dilative, hypertrophic and restrictive.  There are several things that your veterinarian can use to diagnose this problem in your pet.  X-rays of your pet's chest can show how big the heart is and if there are any parts that are larger than the rest. Echocardiography (ultrasound of the heart) shows how well the heart is pumping and any internal defects that may exist.  Finally, an electrocardiogram (ECG) will show if your pet has an abnormal heart rhythm.

Dilative cardiomyopathy is when the heart enlarges and the walls become very thin.  This decreases the heart's ability to pump blood to the rest of the body and eventually results in congestive heart failure.  This type of cardiomyopathy is most common in dogs.  Doberman pinschers, boxers, Irish wolfhounds, great Danes and cocker spaniels have a higher risk of developing this problem, but it has been seen in many breeds including mixed breed dogs.  Age of onset typically is between four and ten years, but occasionally younger dogs are affected.  Signs to look for include difficulty breathing or increased rate of breathing, weight loss, weakness, distension of the abdomen and/or fainting.  Treatment of this condition includes medications to help the heart work better and diuretics combined with a low salt diet to decrease fluid accumulation in the abdomen and the chest cavity.

Hypertrophic cardiomyopathy occurs primarily in cats. Although it has been seen in dogs, it is rare.  In hypertrophic cardiomyopathy, the walls of the heart's ventricles become thickened.  This then leads to enlargement of the atria.  Over time blood pressure will increase and lead to fluid accumulation in the chest.  Cats with this disease are more likely to form clots that can leave the heart and become lodged in arteries. The most common site for the clots to lodge is in the artery that supplies the back legs.  This will cause the rear legs to be weak or paralyzed and they will be cooler than the rest of the body.  It is also a very painful condition.  It is important that treatment for this condition be sought quickly.  Treatment for hypertrophic cardiomyopathy includes low salt diets and diuretics to prevent excess fluid accumulation, drugs to help the heart work more effectively and sometimes aspirin to help prevent clot formation.  Cats with hypertrophic cardiomyopathy should be tested for hyperthyroidism because if it is the cause then treatment for the overactive thyroid can actually reverse some of the heart changes.  Restrictive cardiomyopathy is also seen in cats and is treated similarly to the hypertrophic form, but occurs less frequently.

It is important to keep all animals with cardiomyopathy in a low stress environment.  Exercise is not recommended as it makes the heart work harder.  It is critical that your pet return to the veterinarian for regular check-ups so that the progress of the heart disease can be monitored and treatment adjusted accordingly.