Restrictive Cardiomyopathy (RCM)
What it is
What it does
Who gets it?
How do we look at it?
What do we do about it?
What’s going to happen?
Restrictive Cardiomyopathy (RCM) is a disease of cats. This disease is seen in middle-aged and older cats. Restrictive Cardiomyopathy is a disease where the heart becomes scarred and stiff. This scarring may be the end stage of a thickened heart (Hypertrophic Cardiomyopathy). 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.
In order to understand how the backup affects your pet, a brief synopsis of normal blood flow is helpful. Normally, blood is ejected from the main pumping chamber of the heart (the left ventricle) into the aorta and then to the body. Blood returns from the body to the right heart (first the right atrium, through the tricuspid valve and into the right ventricle) where it is pumped into the pulmonary artery and into the lungs for oxygenation. Blood from the lungs then returns to the left heart (into the left atrium, through the mitral valve and back into the left ventricle).
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.
Therapy is medical in nature. Cats with restrictive cardiomyopathy have a guarded prognosis. Some cats can be very difficult to get under control, but others can be managed with good quality of life for considerable periods. I have managed cats for over 1 1/2 years. 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 have been shown to be effective, though some cardiologists have recommended adding Taurine.
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.
There are certain diagnostic tests that are necessary to accurately diagnose restrictive 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 look for other problems within the heart that might confound therapy. Echocardiograms do not show congestive heart failure, so have some limitations for following the disease. While an echocardiogram might be repeated (especially if things are not going as they should), repeated radiographs are usually much more useful. X-rays (radiographs) are the cornerstone of monitoring your pet. Radiographs show how large the heart is in the chest and how it is enlarging with time, and also show congestive heart failure (pulmonary edema) or other lung problems. Radiographs are often repeated with time to assess response to therapy. An electrocardiogram (EKG or ECG) is very useful to check for rhythm disturbances, 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 (hence the diuretics), 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.