Dilated Cardiomyopathy in Dogs
Dilated cardiomyopathy (DCM) is a heart condition where the muscles of the heart get weak and the heart enlarges like a big balloon. This condition is more common in certain breeds, such as Doberman Pinschers, Boxers, Irish Wolfhounds, Newfoundlands, Dalmatians, Standard/Giant Schnauzers, Cocker Spaniels, and Great Danes. Continue reading to learn more about this form of heart disease, symptoms to monitor for, testing, and treatment options.
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What exactly is dilated cardiomyopathy?
The heart is made of 4 chambers, the two on top are called atria and the 2 chambers on the bottom are called ventricles. The ventricles are the larger chambers. When dogs have DCM, the muscles of the ventricle begin to weaken so the heart can’t pump the blood out efficiently. This leads to the heart enlarging like a balloon.
DCM most commonly affects the left side of the heart. The left side of the heart is responsible for receiving the oxygenated blood that has just left the lungs and then pumping it through the body. The body can compensate for this for a while, even years, but eventually, the blood pressure builds up too high and leads to fluid backing up into the lungs causing heart failure (be sure to read our article on heart failure for more information!).
As the disease continues to progress, the right side of the heart can also become enlarged and lead to fluid buildup in the abdomen and even free fluid in the chest cavity.
Why did my dog develop dilated cardiomyopathy?
Most cases of DCM are thought to be genetic, and certain breeds are passing it along in their gene pool. Boxers, Standard Schnauzers, and Dobermans have a genetic mutation that you can screen for, so be sure to ask your vet about this. The genetic test can be done when your dog is a puppy or anytime in life. It gives you valuable information, so you’ll know if your pet is at higher risk. The test can also help your vet determine what additional annual testing may be recommended to monitor for DCM development to ensure that treatment can be started when needed.
Boxers are also predisposed to developing a specific type of arrhythmia that can lead to DCM. This is also a genetic issue. If your vet notices an unusual heartbeat during the exam or if your Boxer has any fainting spells, further workup of the heart is indicated.
Taurine deficiency is another cause of DCM. Taurine is an amino acid and some breeds like Cocker Spaniels and Golden Retrievers may have an issue metabolizing taurine. Some diets, like vegetarian diets, may not have enough taurine in them and need additional supplementation. A taurine test can be run on your dog to see if supplementation is needed. Many dogs with DCM improve with taurine supplementation if this was the underlying cause. Carnitine, another amino acid, has also been implicated in DCM in breeds like Boxers.
Grain-free diets may also contribute to cases of DCM. If your dog doesn’t need to be on a grain-free diet for allergy or GI reasons, consider a gradual transition to a diet with grains to help reduce this risk of heart disease.
Rarely, DCM can be caused by certain infections.
Symptoms of Dilated Cardiomyopathy
Symptoms are not present in the early stages of DCM. As the heart continues to enlarge and the muscles continue to weaken, symptoms begin to develop. Common symptoms in dogs include:
- Exercise intolerance
- Increased breathing rate and effort, often over 40-50 breaths per minute when resting
- Pale gum color
- Reduce appetite
- Increased heart rate
- Fainting or collapse
- Distended abdomen if the right side of the heart is failing
- Sudden death
What tests are used to diagnose dilated cardiomyopathy in dogs?
There are many tests available and you will get different information with each test, so it can be expensive, but worth the investment.
ECG, or electrocardiogram, is a test to check for arrhythmias. A 24-hour halter monitor is ideal so your vet can get a look at what your dogs’ heart is doing over the course of an entire day. This often requires a referral to a cardiologist and your dog will wear the monitor for a full 24 hours at home and then return the device to the specialist.
An echocardiogram, or ultrasound of the heart, is another common test. This gives your vet or cardiologist a look at how thin the heart walls have become and how much blood the heart can pump compared to normal.
Genetic testing is also ideal, especially in breeds with a higher genetic risk. Most of these tests are just simple blood tests or cheek swabs.
Radiographs, or x-rays, of the chest will also allow your vet to identify an enlarged heart and look for fluid accumulation in the lungs or free fluid in the chest cavity.
ProBNT assay is a blood test to look for a certain peptide that is released when the heart muscles stretch. This is a test to discuss with your vet as part of annual monitoring if you have a breed that is at a higher risk for developing DCM.
My dog has been diagnosed with DCM. What treatments are available?
Luckily, there are medications available to manage DCM, but it’s important to know this is a progressive condition and unless it’s caused by a nutritional deficiency that has been corrected, the heart disease will continue to progress even with medications.
The most common treatment plan involves 2 to 3 medications. A diuretic, like furosemide or spironolactone, is used to help remove excess fluid from the lungs, chest, or abdomen. This will make your dog urinate more often, so it’s very important to have plenty of water available at all times and plenty of potty breaks while on this medication as even well-trained dogs can have accidents.
An ACE inhibitor is also used, such as enalapril or benazepril, to dilate the blood vessels so it’s easier for the blood to exit the heart.
Pimobendan is a newer drug that helps the muscles of the heart contract better and dilates the blood vessels so it’s easier for blood to leave the heart. This medication has been a game-changer for dogs with heart disease and can really help improve their quality of life and prolong survival time.
Dietary changes are another possible part of the treatment plan. If your dog is on a grain-free diet, it would be worth discussing changing to a diet with grains and see if your dogs’ heart condition begins to improve. Supplementation with taurine may be necessary, based on taurine testing.
Treatment of any arrhythmia that may be present is also indicated.
Finally, as DCM progresses and the medications are not as effective or even before starting treatment, your dog may need fluid drained for the abdomen or chest cavity by your vet. This may be needed periodically to keep your dog comfortable.
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