By Dr. Becker
Today I’d like to discuss dilated cardiomyopathy in dogs.
Dilated cardiomyopathy, also called DCM, describes a diseased heart muscle that doesn’t contract or pump efficiently. As the disease progresses, the heart chambers become enlarged, heart valves may leak, and congestive heart failure can develop.
Cause of Dilated Cardiomyopathy Still a Mystery
The cause of DCM is unknown. Unlike heart muscle dysfunction in humans, when it happens in dogs and cats, it’s very rarely the result of chronic coronary artery disease.
Nutritional deficiencies of taurine or carnitine have been linked to DCM in certain breeds. Male dogs seem to develop the condition more often than female dogs. And certain breeds, primarily large breeds, are more prone to DCM, including the Doberman pinscher, Boxer, Scottish deerhound, Irish wolfhound, Great Dane, Saint Bernard, Afghan hound, and Cocker spaniel.
Once in a while, DCM-like heart muscle deficiency develops secondary to an identifiable cause like exposure to a toxin or a heart infection.
Symptoms of DCM
Early in the disease process there may be no obvious symptoms. Some dogs may have a reduction in exercise tolerance. Sometimes a slight heart murmur or other abnormal heart sounds or rhythms can be detected by a veterinarian during a physical exam.
As the heart disease progresses, the heart’s ability to pump declines, so blood pressure in the veins behind the heart can increase.
Congestion of the lungs and fluid accumulation are common. Fluid can also build up in the abdomen and around the lungs, if the right side of the heart is also involved. Congestion and fluid buildup indicate heart failure. Dogs with DCM-induced heart failure often have left-sided congestive failure.
Symptoms include decreased ability to exercise, tiring quickly, increased respiration, and excessive panting and coughing. There may be recurrences of sudden episodes of weakness or fainting. Some dogs with DCM have enlarged abdomens and heavy breathing due to fluid accumulation.
Sudden death can also occur from heart rhythm disturbances, even though there aren’t obvious external signs of heart disease. Advance signs of heart failure include labored breathing, reluctance to lie down, and the inability to get comfortable. A worsening cough, reduced activity level, loss of appetite, as well as collapse, can all be symptoms.
Often owners of dogs with DCM feel as though their pet developed heart failure very quickly. But the underlying disease and damage to the heart muscle has actually been going on for months or even years in most cases.
In addition to a physical examination, your vet will need to run medical tests to confirm a diagnosis of DCM and determine the severity of the disease.
Keep in mind your vet can’t, for example, know the size of your pet’s heart by listening with a stethoscope. Sometimes a heart can sound pretty normal on auscultation (which is what vets do when they listen with a stethoscope), but there can be really significant changes going on inside the heart that are undetectable without additional tests.
The proBNP test is a simple blood test with a fast turnaround time that can detect a problem very early in the disease process by measuring the amount of peptide hormone in your pet’s blood. This hormone is only released when the heart is pushed beyond its capacity. If your vet doesn’t suggest a BNP blood test, I recommend you ask for it.
X-rays may also show enlargement of the heart chambers, and can also indicate the presence of fluid in the lungs.
An EKG can reveal atrial fibrillation and tachycardia, which means a rapid heart rate.
A heart ultrasound called an echocardiogram is also necessary for a definitive diagnosis of this disease. This test looks at the size of the heart and its ability to contract. If DCM is present, the heart chambers are enlarged and there’s compromised contraction of the muscle. The echocardiogram can also be used to detect signs of early DCM in breeds that are at higher risk for the disease.
Treatment of dilated cardiomyopathy focuses on improving heart function and treating symptoms of congestive heart failure.
Conventional treatment involves the use of a variety of medications. ACE inhibitors are often prescribed to slow down the progressive changes to the heart that can lead to heart failure.
As the disease progresses, different drugs can be used to help the heart contract. Drugs can be administered to slow down a rapid heart rate, to manage accumulation of fluid in the lungs, or to dilate blood vessels. There are actually some drugs that can help the heart beat and pump more efficiently as well.
All of these drugs require careful monitoring for side effects. And unfortunately, side effects are rampant and can include electrolyte imbalances, reduced appetite, diarrhea and vomiting, depression, a drop in blood pressure, as well as kidney disease.
Veterinary cardiologists often combine medications, which makes careful monitoring of the patient that much more important.
Therapy for DCM is individualized for the patient’s specific symptoms. In recent years, a small number of dogs have had defibrillators surgically implanted to manage life-threatening arrhythmias.
Unfortunately, because the disease is irreversible and heart failure is typically progressive, the drugs and dosages required to manage DCM usually increase over time.
Alternative therapies that can support heart function include herbs such as Hawthorne berry and cayenne. Supplements can also be very beneficial, including acetyl L-carnitine, the amino acid taurine, arginine, D-ribose, omega-3 fatty acids, and ubiquinol.
Of course, feeding a fresh food diet that is rich in naturally occurring amino acids will be the very best food therapy for a dog with DCM, and can also help nourish breeds predisposed to this medical problem.