Ron Hines DVM PhD 6/24/06

Cardiomyopathy or the death of heart muscle occurs in two forms. In the first form, the loss of cardiac muscle causes the heart to balloon (dilated cardiomyopathy). In the second form, the muscular walls of the heart actually thicken but the strength of contractions decrease (hypertrophic cardiomyopathy). When the heart begins to fail a number of signs occur. Blood pools in the veins of the body and lungs causing congestion and edema. The leg swelling we see in humans with this condition does not occur in ferrets. Instead, fluid accumulates in the abdomen giving the ferret a pot-bellied appearance. These ferrets tend to breath rapidly and shallow. Their pulse rate goes up in an attempt to keep the body oxygenated. If you lift your ferrets lips you will see that the gums are no longer a uniform pink. Instead, they are bluish or grayish and color comes back only slowly when the gums are pinched. This is called slowed capillary refill time. Normal capillary refill time in your ferret is less than three seconds.

Hypertrophic Cardiomyopathy
In hypertrophic cardiomyopathy the individual muscle fibers of the heart actually thicken. However, this increase in size actually lessens the effectiveness of the heart in pumping blood. Although the size of the ferret’s heart remains the same, the sizes of the chambers within the heart decrease. These small chambers are apparent when the pet is autopsied and the heart muscle is cut into two sections. Because the heart shadow on x-rays remains normal, we diagnose this condition based on clinical signs and ultrasound and abnormal electrocardiogram.

Treatment Of Hypertrophic Cardiomyopathy
The most important drugs used to treat this condition are the diuretic furosemide (Lasix, 1mg/pound twice or three times a day) and the ACE inhibitor, enalapril (Vasotec, Enacard, Merck, 0.125 – 0.25mg/pound every 24-48 hours). Enacard should not be used if blood tests show signs of kidney disease. The calcium channel blocking drug, diltiazem (Cardizem, Merrill Dow 0.75 – 3.75mg/pound twice a day) and the beta blocker, atenolol (Tenormin ICI, 6.25mg/ferret daily) are also helpful in extending the ferret’s life.

Dilated Cardiomyopathy
This form of heart disease is more common than the hypertrophic form. It is commonly called congestive heart failure. The greatly enlarged, thin-walled heart becomes ineffective in pumping blood. Besides signs already mentioned, a wet cough and lethargy are common with this disease. It is quite common to hear heart murmurs in these animals.The cough becomes worse when the ferret is laying down at rest. Labored respiratory effort is more abdominal than thoracic and occurs due to fluid accumulating within the chest and abdomen. Radiographs of the ferret show an enlarged heart with fluid accumulation in both body cavities.

Treatment of Dilated Cardiomyopathy
As with hypertrophic cardiomyopathy, no cure exists for this disease. A recent advancement in human medicine involves placing the heart in a mesh sac that prevents its ballooning enlargement. But for now in ferrets we must be content with eliminating pooled fluids with diuretics such as Lasix, reducing peripheral resistance to blood flow with Enacard, and increasing the force of heart contractions with inotrophic digitalis agents (Digoxin, Cardoxin 0.0025 – 0.005mg/pound once or twice a day).

Other Drugs That May Be Effective

Vetmedin (pimobendan)

Vetmedin works by increasing the amount of calcium available to the heart muscles and also lowers vascular resistance and blood pressure (increased blood vessel diameter or vasodilatation). In doing so, the pet’s heart needs to do less work.
Vetmedin increases blood calcium levels. The more calcium that is present, the stronger are the heart’s contractions. The Drug was originally used in human medicine about 10 years ago. At the time, it was thought that it might offer hope to people with heart conditions similar to your pet’s. It did increase the force of human heart contractions, but it sometimes made the hearts pump too forcefully. Dogs and cats do not develop coronary artery disease as humans do. But human hearts with blocked or occluded coronary arteries became starved for oxygen when on this drug. This led to heart attacks and angina (chest pain). Because dog and cat hearts differ from human hearts in this respect, the drug has been reintroduced in Europe and Canada for use heart failure in pets. The published dose of Vetmedin is 0.1-0.3mg/ pound body weight/day. It should be given about an hour before meals with half the dose given before breakfast and half before supper. I obtained this dose from Boehringer-ingelheim’s Spanish language website. Their Dutch website gives the minimum daily dose as 0.15mg/lb/day. An occasional dog will experience vomiting on this drug.

Forticor (benazepril HCl, Lotensin, Novartis Animal Health, Canada, etc.)
Benazepril is also an angiotensin-converting enzyme (ACE) inhibitor drug. It is similar in it’s effect to enalapril (Enacard) and Vetmedin. Forticor is used to increase the efficiency with which failing hearts pump blood and is also used to treat high blood pressure in pets. In the liver, the drug is metabolized to benazeprilat, the active compound. The dose of Forticor is 0.125-0.25mg/lb given once a day or divided into two daily doses. I can be given with or without food. It is also effective in lowering blood pressure (hypertension) in cats with kidney failure.

Spirolactone (Aldactone)
When the maximum dose of furosemide diuretic (0.5-1.5mg/ pound every 8-12 hrs ) is not sufficient to eliminate fluid buildup in the tummy (ascites) and lungs (pulmonary edema) of your pet, another diuretic, such as spirolactone, can be added to the medications your pet receives. The usual spirolactone dose is 0.5-1.0mg/pound body wt. given twice a day (1-2mg/lb/day). You need to be patient - it takes 2-4 days for the full effect of the drug to be reached. Spirolactone can increase the toxicity and effect of digoxin so your pet’s digitoxin dose may need to be lowered. It can also cause an increase in serum potassium, which can be dangerous. To monitor potassium, a blood sample should be taken and measured for serum electrolytes and kidney function on the 3rd or 4th day, the 7th day and periodically there after.

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