Canine Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a disease of the heart muscle which causes the heart to enlarge and not function properly. The disease usually afflicts larger breeds of dogs such as the Doberman pinscher, Scottish deerhound, boxer, Newfoundland, golden retriever, Labrador retriever, and the Irish wolfhound. However, it can also affect both the English and American cocker spaniel and rarely, other small breeds of dogs. The occurrence of dilated cardiomyopathy increases with age and typically has an age of onset between 4 and 10 years. The cause of DCM in dogs is still unknown; however, many factors suggest a genetic cause.

Dilated cardiomyopathy usually affects both the left and right sides of the heart with either side being more severely affected. Typically, both the ventricle (lower chamber) and the atria (upper chamber) enlarge and the ventricle loses its ability to contract and pump blood out to the body or the lungs. The consequence of the heart failing in its ability to pump blood can be compared to a simple mechanical pump. If the sump pump in your basement fails, water backs up into the basement; if the left heart fails, fluid backs up into the lungs and if the right heart fails, fluid backs up in the abdomen or space surrounding the lungs.

Long term prognosis for dilated cardiomyopathy varies considerably. Unfortunately, most dogs with signs of heart failure at the time of diagnosis die as a result of the disease within 6 months to two years. Unfortunately, some dogs, especially certain breeds with a more severe form of the disease may survive only weeks to a couple of months.

Treatment of dilated cardiomyopathy is aimed at both improving the heart's function and controlling the signs of congestive heart failure. Drugs such as Lanoxin (Digoxin, Digitalis) are used to help the heart contract better and to slow the heart rate down if certain arrhythmias exist. Once your dog is started on Lanoxin, you will be asked to watch for signs digoxin toxicity that, although uncommon, include loss of appetite, vomiting, diarrhea, and lethargy. These adverse signs can hopefully be avoided by having a blood test run by your regular veterinarian 7 to 14 days after the drug is initiated. To check for appropriate levels of Lanoxin in the bloodstream, a blood test must be drawn 6 to 8 hours after your dog’s morning dose of the Lanoxin. However, if any of these signs do occur, please call our office or your regular veterinarian. If these signs are severe, you can stop the Lanoxin and then call us; however, if the signs are mild, the ideal situation would be to go to your regular veterinarian and have a Digoxin level drawn so that we can be sure that the drug is causing the problems and the signs are not
related to something else.

Diuretics are also used to help both control and prevent accumulation of fluid in or around the lungs. Lasix (Furosemide) is usually the drug of choice. Potential side effects of diuretic use include increased thirst and potentially increased urination. Another essential drug that is used in the treatment of dilated cardiomyopathy is termed a balanced vasodilator. This helps the heart pump more effectively against the pressures of the arteries and veins. Examples of this drug include Vasotec, Enacard, Zestril, Prinavil, and Lotensin. These drugs are usually started gradually with a low dose and then building up to your dog's required dosage. These drugs can occasionally interact with the kidneys. For this reason, you will be asked to see your regular veterinarian in 7 to 10 days, in 4 weeks, and then every three months to have a chemistry blood panel checked to assure that kidney function is preserved.

Other drugs utilized in the treatment of dilated cardiomyopathy are aimed at controlling cardiac arrhythmias (electrical disturbances in the heart). Arrhythmias can be very problematic in some cases of DCM and can even be life threatening. Certain breeds are more predisposed to this additional problem. If possible, it is a good idea to buy an inexpensive stethoscope to monitor your dog's heart rate and rhythm. Keep a journal of these records and if you are seeing a progressive increase or decrease in your dog's heart rate or hear an irregular heartbeat, please call our office.

It is also important for you to monitor your dog's overall attitude and outward signs. If you notice any heavy/labored breathing, coughing, fainting spells, restlessness, or profound lethargy, please call us or see your regular veterinarian as soon as possible.