What is Dilated Cardiomyopathy in Dogs?

Introduction

For years, Jenna and her energetic Doberman, Rocky, had been inseparable, spending countless hours exploring the great outdoors together. Recently, however, Jenna noticed that Rocky was becoming increasingly lethargic and short of breath after even short walks. Concerned about her beloved companion’s well-being, Jenna took Rocky to the veterinarian for a comprehensive examination. The vet diagnosed Rocky with dilated cardiomyopathy, a serious heart condition that can affect dogs.

Enlarged heart chambers, decreased contractility, and thickened walls characterize dilated cardiomyopathy. As the heart becomes more prominent, it cannot pump efficiently. According to the Veterinary Medical Database (Sisson et al., 2000), from 1986 to 1991, 0.5% of the dogs evaluated at U.S. referral hospitals were diagnosed with DCM.

Dilated cardiomyopathy is relatively common in large-breed dogs. Up to 10% of Labrador Retrievers and Golden Retrievers are estimated to suffer from this condition. In dogs, DCM occurs most often between two and five years old. Unfortunately, there is no cure for DCM, but treatment may slow its progression.

What Causes Dilated Cardiomyopathy in Dogs?

Dilated Cardiomyopathy (DCM) is an inherited disorder that affects the heart muscle. DCM causes the left ventricle (the heart’s main pumping chamber) to enlarge and weaken, leading to congestive heart failure (CHF).

There are several theories regarding the cause of dilated cardiomyopathy. One idea is that the condition results from a mutation in one of the genes involved in cardiac development. Another approach is that viral infection causes the disease.

While the exact cause of DCM is unknown, research suggests that genetics play a role. Several breeds are predisposed to developing dilated cardiomyopathy, including Boxers, Golden Retrievers, German Shepherd Dogs, Labrador Retrievers, Rottweilers, Bull Terriers, and American Pitbulls. In addition, Doberman Pinschers have a reported incidence rate of 50% in males and 33% in females (Oyama, 2015), while Irish Wolfhounds have an overall breed incidence of 25%.

There are two types of DCM: primary and secondary.

• Primary dilated cardiomyopathy is caused by genetic mutations that result in abnormal protein production. It is inherited in both purebreds and mixed breeds. Several genes are involved in causing the disorder, including TNNT2, MYH7, ACTC1, and DES, and some of these genes are dominant, while others are recessive.
• Secondary dilated cardiomyopathies are usually associated with other conditions, such as endocrinological disorders, neoplasia, or infectious diseases. Secondary forms of dilated cardiomyopathic conditions are less common. These include congenital, nutritional, toxic, inflammatory, and idiopathic. Congenital cases are due to problems during fetal development, and healthy subjects are related to dietary deficiencies. Toxic cases are linked to environmental toxins. Inflammatory issues are due to autoimmune reactions. Idiopathic cases are unknown.

Dilated Cardiomyopathy in Dogs May Cause Other Diseases?

Other diseases associated with dilated cardiomyopathy include arrhythmogenic right ventricular dysplasia (ARVD), hypertrophic cardiomyopathy (HCM), and restrictive cardiomyopathy (RCM). These conditions share similar characteristics with DCM.

• Arrhythmic right ventricular dysplasias (ARVD) is a rare form of cardiomyopathy affecting the heart’s right side. Symptoms include cough, exercise intolerance, and sudden death. ARVD is diagnosed based on clinical signs, electrocardiography, echocardiography, histology, and genetic testing.
• Hypertrophic cardiomyopathy is another type of cardiomyopathy. Unlike DCM, HCM is characterized by the thickening of the left ventricle wall. Hypertrophy usually begins in adulthood and progresses over time.
• Restrictive cardiomyopathy is a form of cardiomyopathy that affects the left side of the heart. Restrictive cardiomyopathy causes the left ventricles to thicken and weaken.

Are There Any Other Types of Cardiomyopathy in Animals?

Yes! There are other types of cardiomyopathy in animals. For example, amyloid cardiomyopathy is caused by deposits of a protein called amyloid in the heart. The exact cause of amyloid cardiomyopathy is unknown. Amyloid cardiomyopathy typically develops in middle-aged cats and dogs. Cats tend to die suddenly, whereas dogs tend to experience progressive deterioration of their hearts.

Symptoms of Dilated Cardiomyopathy in Dogs

Symptoms include:

• coughing
• exercise intolerance
• weakness
• poor quality of life
• irregular heart rhythm
• sudden death.

Diagnosis of DCM in Dogs

A European study showed that 1.1% of the dogs seen at veterinary hospitals were diagnosed with DCM (Fioretti and Delli, 1988). Therefore, the first step in diagnosing DCM is excluding secondary heart failure causes. This includes ruling out coronary artery disease, hypertension, valvular heart disease, pulmonary embolism, thyroid disorders, hyperthyroidism, pericarditis, and pheochromocytoma. If no secondary cause is identified, further testing is needed to determine whether DCM is present. 

Echocardiography is the primary diagnostic test used to detect DCM. Echocardiograms measure the size and shape of the heart chambers and assess their movement during contraction and relaxation. They provide valuable data regarding the overall health of the heart muscle. Other tests may be an electrocardiogram, exercise stress testing, and blood samples. Genetic testing is available for those with familial forms of DCM. 

Your vet should perform a thorough physical examination to determine whether your dog suffers from dilated cardiomyopathy. They will listen to your dog’s heartbeat during the exam and check its rhythm, and they will also measure the size of the chest cavity and abdomen.

They will also check the lungs for signs of pneumonia. In addition, they will examine the eyes and ears.

Depending on the severity of the disease, your vet may recommend genetic testing, echocardiography, electrocardiogram (ECG), or cardiac catheterization.

Genetic testing is used to detect specific mutations in genes associated with cardiomyopathy. These tests can reveal whether a conversion exists in your dog’s DNA.

An ECG records electrical activity in the heart, and an abnormal ECG pattern indicates that your dog has cardiomyopathy. However, an ECG cannot always distinguish between different forms of cardiomyopathy. For example, an arrhythmia such as atrial fibrillation can cause an abnormal ECG.

Using X-ray imaging, your vet can see the heart and other organs inside, allowing them to diagnose problems with the heart’s valves, arteries, veins, and other structures.

Treatment for Dogs with Dilated Cardiomyopathy

If your dog has dilated cardiomyopathy, he may need treatment. Treatment options include medications, dietary modifications, and surgery. Some dogs live longer than others with this condition, so keep an eye on him and contact your vet if his health declines.

Medications

The most common medications used to treat dilated cardiomyopathy are beta-blockers, such as Cordarone, Propanolol, and Acebutolol, as well as diuretics and ACE inhibitors.

Beta-blockers work by helping the heart muscle relax, improving blood flow, and allowing more oxygen to get to the heart. Diuretics help reduce fluid build-up in the lungs by promoting urination and reducing the amount of sodium and chloride in the bloodstream. ACE inhibitors reduce the number of stress hormones released into the bloodstream while raising nitric oxide levels, which helps relax constricted blood vessels.

In addition to these medications, several natural supplements are available as an alternative or adjunct therapy for dilated cardiomyopathy in dogs. Omega-3 fatty acids from a fish or krill oil-rich diet can help improve myocardial contractility and promote healthy circulation. Other herbs that may be beneficial include Hawthorn berry, CoQ10, Dandelion root, Crataegus oxyacantha extract, Curcumin extract, etc.

Dietary Modifications

Some diets are beneficial for treating DCM. For example, a diet high in omega-3 fatty acids may slow the progression of the disease. Omega-3 fatty acids are found in fish, amino, and flaxseed oils. In addition, flaxseed oil contains lignans, which may protect against cancer.

Surgical Procedures

Some dogs with DCM require surgical procedures to repair damaged heart tissue. Surgical procedures include:

• Myectomy

Myectomy is the most widely used surgery for treating DCM and involves removing portions of the heart muscle affected by the condition. This helps to reduce strain on the heart and improve its efficiency. The procedure can also improve the chances of restoring more normal cardiac function.

• Mitral valve replacement

Another surgical option is mitral valve replacement, which replaces a faulty mitral valve with a new prosthetic valve made from animal tissue or synthetic materials. This can help restore normal blood flow through the heart and improve symptoms.

• Heart transplantation

This procedure replaces the diseased heart with a healthy donor heart. Some dogs may benefit from heart transplantation in advanced stages of DCM when other treatments have failed to provide relief.

How Do I Prevent Dilated Cardiomyopathy in My Dog?

Preventing dilated cardiomyopathy in your dog ensures they live a long and healthy life. The first step is understanding what can lead to the condition. Dilated cardiomyopathy can occur due to genetic issues, exposure to toxic substances, nutritional deficiencies, viral or bacterial infections, or certain medications.

To prevent dilated cardiomyopathy in your pup, ensure their diet contains an appropriate balance of proteins and other essential nutrients. Feed a balanced, nutrient-rich diet according to your vet’s recommendations and supplement with natural remedies such as garlic powder or seaweed. Also, watch for signs of infection that could put your pup at risk for dilated cardiomyopathy.

Be sure to monitor any medications (together with your veterinarian’s advice), as some may worsen the condition or even cause it in the first place. Finally, regularly schedule vet visits so you can keep up on preventative care and maintain a comprehensive understanding of your pet’s health – catching any issues before they become full-blown heart diseases!

Frequently Asked Questions