What Is Dilated Cardiomyopathy in Dogs?
Dilated cardiomyopathy (DCM) stands as a prevalent heart condition found in large-breed dogs. In DCM, the heart of the dog enlarges due to the weakening of the heart muscle, causing it to become thinner and more stretched out.
The heart comprises four chambers organized in a square configuration. The upper chambers consist of the left and right atriums, while the lower chambers include the left and right ventricles. Blood initially travels from the body into the right side of the heart, proceeding into the lungs through the pulmonary arteries. Within the lungs, the blood acquires oxygen, which it transports back into the left side of the heart before being pumped throughout the body. This vital process ensures that the body’s cells receive the necessary oxygen for their functions.
Oxygenated blood facilitates various bodily functions in dogs. It sustains the muscles in their legs, enabling activities like running, jumping, and playing. It aids in the digestion of food and the absorption of nutrients in their intestinal tract. Additionally, it supports the kidneys and liver in eliminating toxins and waste from the blood. Every organ in a dog’s body relies on the oxygen-rich blood supplied by the heart. However, in dogs affected by DCM, the ventricles gradually weaken, becoming thin and feeble. Consequently, they struggle to pump oxygen-enriched blood effectively throughout the body.
While DCM progresses slowly over time, its symptoms are often subtle and may go unnoticed by pet owners. However, dogs with DCM can suddenly experience heart failure, requiring immediate emergency care. Moreover, DCM may advance to congestive heart failure (CHF), posing a critical medical emergency as it can lead to fatality within hours.
Symptoms
Symptoms of Dilated Cardiomyopathy (DCM) in dogs can manifest abruptly. Even seemingly healthy dogs may exhibit serious clinical signs or even experience sudden death. These symptoms often stem from either a deficiency of oxygenated blood circulating throughout the body, leading to fatigue or decreased appetite, or fluid accumulation in the lungs due to heart failure, resulting in breathing difficulties.
Signs indicating DCM include:
- Rapid breathing
- Difficulty finding a comfortable position or lying down, restlessness
- Bluish discoloration of the gums or tongue
- Wet cough or hacking
- Increased effort during breathing, noticeable chest movements
- Easily getting tired, inability to tolerate exercise
- Lethargy or weakness
- Reduced appetite
- Swollen abdomen
- Fainting spells or sudden collapses
Causes
The causes of Dilated Cardiomyopathy (DCM) in dogs can be attributed to various factors, including genetics, nutrition, and infections. Genetic predisposition has long been associated with DCM, as certain breeds have a higher likelihood of being affected.
DCM primarily affects large-breed dogs, with the following breeds being most commonly affected:
- Doberman Pinschers
- Irish Wolfhounds
- Boxers
- Saint Bernards
- Newfoundlands
Although DCM is more prevalent among large-breed dogs, English Springer Spaniels, Cocker Spaniels, and Portuguese Water Dogs also carry an inherited trait that increases their susceptibility to the condition.
Grain-Free Food and DCM in Dogs
In 2018, the U.S. Food and Drug Administration, along with the Food and Drug Administration’s Center for Veterinary Medicine, initiated an investigation into the potential link between grain-free diets and dilated cardiomyopathy (DCM) in dogs. This investigation was prompted by observations from veterinary cardiologists who noticed an increase in DCM cases among dogs not genetically predisposed to the condition, such as Golden Retrievers.
In 2019, the FDA released a report revealing that over 90% of reported DCM cases involved dogs fed grain-free diets. Many of these diets contained peas, legumes, or lentils as primary ingredients instead of traditional grains. Some of the implicated diets included raw food, vegetarian, or vegan options.
This investigation sparked discussions within the veterinary community regarding “BEG” diets, which stands for boutique, exotic, and grain-free diets. Initially, it was hypothesized that a potential deficiency of taurine, an essential nutrient, in these diets might be the issue. This assumption stemmed from reports indicating positive responses in many Golden Retrievers with DCM to taurine supplementation. However, further research suggested that DCM might be more complex than a single ingredient issue, with various factors potentially contributing to its development.
While many veterinarians caution against feeding grain-free diets, some dogs with allergies may require specific BEG diets to manage their condition. It is crucial to consult your veterinarian regarding proper nutrition and what suits your pet’s health and well-being best. They may recommend consulting a veterinary nutritionist to devise a customized diet tailored to your pet’s requirements.
If you are considering feeding your dog a BEG, vegetarian/vegan, raw, or homemade diet, it’s essential to discuss recommended monitoring with your veterinarian to prevent secondary acquired nutritional diseases like DCM. Your veterinarian might suggest measuring blood and plasma taurine levels, supplementing with specific vitamins or minerals, or more frequent imaging to ensure that your dog’s diet is not causing any health issues.
Diagnosis
Diagnosing Dilated Cardiomyopathy (DCM) in dogs involves a series of tests conducted by veterinarians. Initially, your veterinarian will listen to your dog’s heart to detect any murmurs or abnormal rhythms (arrhythmias). They will also assess lung sounds for signs of fluid buildup, indicated by dampened or crackling sounds. X-rays will be taken to examine the size of the heart and identify any enlargement or fluid accumulation.
Furthermore, blood tests and urine analysis may be performed to screen for underlying kidney disease, as DCM and kidney issues often coexist. Additionally, a ProBNP test may be conducted to detect elevated levels of a specific protein associated with heart muscle stretching or damage.
If DCM is confirmed or suspected, your veterinarian may suggest referral to a veterinary cardiologist. The cardiologist will perform an echocardiogram, a heart ultrasound that enables them to visualize each chamber of the heart and observe blood flow patterns. An electrocardiogram (ECG) will also be conducted to assess the heart’s electrical activity and identify any abnormal rhythms.
Treatment
The treatment of Dilated Cardiomyopathy (DCM) in dogs primarily involves medications aimed at reducing the heart’s workload, improving its efficiency, and alleviating fluid buildup in the lungs to facilitate easier breathing.
While DCM cannot be cured, early detection of nutritionally acquired DCM can lead to the restoration of normal heart function with appropriate therapy. Common medications prescribed for dogs with DCM and congestive heart failure include:
- ACE inhibitors such as enalapril or benazepril, which dilate the veins leaving the heart, reduce resistance, and ease blood pumping from the heart to the body.
- Diuretics like furosemide or spironolactone, which assist in removing excess fluid from the lungs, easing breathing in dogs with congestive heart disease.
- Inotropic drugs like pimobendan, which enhance heart muscle strength by increasing the force of heart contractions and reducing pressure in arteries and veins.
- Beta blockers including sotalol, atenolol, and carvedilol, which act as anti-arrhythmic drugs. Calcium channel blockers like diltiazem may also be prescribed by a cardiologist to address irregular heart rhythms by affecting the heart’s electrical channels.
Nutritional therapy may also be incorporated into the management of heart disease. This may involve sodium-restricted diets such as Royal Canin Veterinary Diet Cardiac or Hills Prescription Diet h/d. Additionally, supplements like taurine, coenzyme Q10, or carnitine may be recommended.
Bronchodilators like theophylline and cough suppressants such as hydrocodone or butorphanol may be prescribed to facilitate easier breathing and reduce cough frequency associated with congestive heart failure.
Living and Management
The management of Dilated Cardiomyopathy (DCM) in dogs is a lifelong commitment. Heart disease progresses gradually, and several factors influence the prognosis, including the dog’s breed, whether the disease is nutrition-related, and the severity of the condition at diagnosis.
Certain breeds, such as Doberman Pinschers, may experience more aggressive forms of DCM, often resulting in an average survival time of about three months post-diagnosis. Conversely, breeds like Cocker Spaniels typically exhibit a slower progression of the disease, with an average survival time ranging from six months to two years following diagnosis.
Addressing a taurine deficiency, if present, can significantly improve heart function. However, if a dog is already experiencing congestive heart failure at the time of diagnosis, it may worsen their prognosis. Dogs diagnosed early in the course of dilated cardiomyopathy generally have a more favorable prognosis and may enjoy comfortable lives for many years to come.