Hypertrophic Cardiomyopathy (HCM)


 

 

What it is
  • Hypertrophic Cardiomyopathy is a disease where the heart gets thickened and stiff.
What it does
  • Because the heart is stiff and blood has difficulty in entering the ventricles properly, it causes blood to back up and force fluid into either the lungs or into body cavities.
    • If the ventricles do not accept blood properly, the ventricles and atria get enlarged, and pressure builds up in the left or right atrium. Blood then ‘backs up’, and causes fluid in the lungs or body cavities to accumulate.
    • Fluid in the lungs is called left congestive heart failure or pulmonary edema.
      • Animals with pulmonary edema breath more rapidly and cough due to the fluid, and cannot exercise well.
    • Fluid in the body cavities is called right congestive heart failure
      • Fluid in the chest is called pleural effusion, and fluid in the abdomen is called ascites.
      • Cats rarely develop ascites.
      • Animals with pleural effusion breath heavily and are lethargic and do not eat well. Some animals will also faint with exercise or excitement.
Who gets it?
  • HCM is seen most often in cats, and rarely in dogs
  • There are different forms of the disease
    • Juvenile onset
      • Young animals
      • Young and purebred
        • Ragdoll- ~ 15 months
        • Maine coon- ~2.5 years
        • Sphynx- ~3.5 years
    • Middle age
      • Domestic short hair cats- ~8 years
      • Persian- ~8 years
  • Genetic in origin
    • Maine coon, Ragdoll, American shorthair, Sphynx
  • Predisposed
    • Bengal, Birman, British shorthair, Domestic shorthair, Himalayan, Norwegian forest cat, Persian, Rex, Scottish fold, Siberian, Turkish Van
How do we look at it?

There are certain diagnostic tests that are necessary to accurately diagnose hypertrophic cardiomyopathy, to tell you how bad the problem is, what can be done about the problem, and what you can expect in the future for your pet.

  • An echocardiogram (or heart ultrasound) is used to look within the heart, confirm the diagnosis, and to evaluate how stiff the heart is.
    • Echocardiograms are the most useful modality for this disease, and are what used to follow animals through time.
  • X-rays (radiographs) show how large the heart is in the chest, and also show congestive heart failure (pulmonary edema) or other lung problems.
    • Radiographs are often repeated to assess response to therapy if there is congestive heart failure.
  • An electrocardiogram (EKG or ECG) is very useful to check for rhythm disturbances
    • and is not very useful otherwise
  • Labwork is very important, because hearts with disease do not handle water loads very well, but kidneys require water load to maintain function.
    • Usually, there is a wide area to work within where the heart and the kidneys are both happy.
      • Ifkidney function is marginal, kidney failure can occur.
What do we do about it?
  • Therapy is medical in nature.
    • Many animals will not need any therapy early in the course of disease
What’s going to happen?

 

Therapy is medical in nature. Some cats with hypertrophic cardiomyopathy will do very well with or without medication. Other cats with other characteristics may survive for up to 5 years with medical therapy, with about 20% dying per year. Newer advances in medical therapy have prolonged survival, and these pets can have excellent quality of life. The goals of therapy are to maintain your pet out of congestive heart failure for as long as possible on a minimum of medication, for them to feel well and to be playful, and for them to eat well. No nutritional supplements are effective.

Lower salt diets do not taste as good as regular diets, and many cats will not eat them. A severely restricted salt diet such as “Heart diet or H/D” is often not eaten well at all by cats, so I recommend a slightly less restricted diet called “Kidney diet or K/D”. There are other companies that make similar products to K/D, and they are typically fine to use. It is more important that your pet eat and eat well, than to stick to the salt restricted diet, even if they won’t eat it. Some cats require mixing in canned food or meat-based baby food. The medications are powerful, and will usually work even if your pet is on regular food. Do not give high salt items such as pork and salted popcorn or high-salt treats.

An echocardiogram (or heart ultrasound) is used to look within the heart, confirm the diagnosis, and to look for other problems within the heart that might confound therapy. Echocardiograms are the most useful modality for this disease, and are what I use to follow animals through time, especially if there is no signs of congestive heart failure. Echocardiograms do not show congestive heart failure, so do have some limitations. X-rays (radiographs) show how large the heart is in the chest, and also show congestive heart failure (pulmonary edema) or other lung problems. Radiographs are often repeated with time to assess response to therapy if there is congestive heart failure. An electrocardiogram (EKG or ECG) is very useful to check for rhythm disturbances (but is not very useful otherwise), and may be repeated to assess response to certain medications. Labwork is very important, because hearts with disease do not handle water loads very well , but kidneys require water load to maintain function. Usually, there is a wide area to work within where the heart and the kidneys are both happy, but if kidney function is marginal, kidney failure can occur.

Monitoring at home consists of monitoring eating and activity, and to note breathing patterns. Because fluid in the lungs or chest causes increased breathing rates as the first sign of congestive heart failure, noting breathing rates is very important. Breathing rates in animals can only be accurately assessed when they are asleep and it is cool out. Their sleeping breathing rates should be about 30 breaths a minute or less (about a breath every other second). If heart failure is developing, sleeping breathing rates increase to about 60 breaths a minute (or one breath a second). If this occurs for a couple of nights, your pet should be represented, and may need repeat radiographs to document congestive heart failure, and medical adjustments may be necessary. Congestive heart failure, heart disease itself, or the medications used for heart disease can cause lack of appetite. Sometimes the cause of lack of appetite can be difficult to ascertain, requiring repeat radiographs and labwork, or medication adjustment to find the cause of lack of appetite.