Dilated Cardiomyopathy in Dogs: How to Spot the Signs

As a dog lover and veterinarian, one of the most devastating diagnoses I encounter is dilated cardiomyopathy (DCM). This serious heart condition can strike fear into any owner‘s heart – and for good reason. DCM is the most common type of heart disease in dogs and often sneaks up silently, only showing signs once the disease is very advanced.

While DCM can affect any breed, it most commonly targets large and giant breed dogs in the prime of their life, between 4-8 years old. If you have a Doberman Pinscher, Great Dane, Irish Wolfhound, Boxer, or other big dog, this article is a must-read. Early detection is critical, so I‘m sharing everything you need to know about DCM in dogs, including the subtle signs to watch for and steps you can take to protect your pup‘s ticker.

What is Dilated Cardiomyopathy?

First, let‘s cover the basics. Dilated cardiomyopathy is a disease of the heart muscle that causes the chambers to enlarge and the walls to become thin and weak. This makes it harder for the heart to pump blood effectively, leading to congestive heart failure. The left ventricle (lower heart chamber) is usually affected first, but DCM can progress to involve both sides.

There are two main categories of DCM:

1. Primary DCM – This is thought to be genetic and is most common in large breeds like Doberman Pinschers, Great Danes, Irish Wolfhounds, Newfoundlands, and Boxers. Portuguese Water Dogs and Cocker Spaniels are also over-represented.

2. Secondary DCM – Develops due to an underlying disease process, such as hypothyroidism, Cushing‘s disease, chronic tachycardia (fast heart rate), infections, or nutritional deficiencies. A link has also been found between grain-free, exotic ingredient diets and DCM.

The Silent Killer: Spotting DCM Before Symptoms Appear

DCM is often called the "silent killer" because it can progress for months to years before any outward signs appear. Once symptoms emerge, the disease is usually quite advanced. This is why proactive screening is so important for at-risk breeds.

The first asymptomatic stage is called occult DCM. During this phase, the heart undergoes microscopic changes and begins to enlarge, but the dog still appears healthy. It can only be detected with specialized tests:

• Holter monitor – A wearable ECG device that records the heart rhythm for 24-48 hours. Doberman Pinschers and Boxers should have annual Holters after age 4 to check for premature ventricular contractions (abnormal heart beats), which can be an early indicator of DCM.

• Echocardiogram – An ultrasound of the heart that measures chamber size and wall thickness. Recommended for large/giant breed dogs over age 5 and those with heart murmurs or an abnormal Holter.

• Cardiac biomarkers – Blood tests that detect proteins released by damaged heart cells, like cardiac troponin I and N-terminal pro B-type natriuretic peptide (NT-proBNP). Elevated levels may indicate early DCM.

At-risk dogs should have annual exams with their veterinarian, including auscultation (listening to the heart), to check for subtle abnormalities. In the early stages, the only clue might be a soft heart murmur, arrhythmia, or weak pulses.

Signs of DCM: Know the Symptoms

Once DCM reaches the clinical stage, dogs develop signs of congestive heart failure:

1. Coughing – Often worse at night or after rising. Caused by fluid backing up into the lungs.

2. Rapid breathing or panting at rest – Over 30 breaths per minute is a red flag.

3. Difficulty breathing – Increased effort, extending head and neck to breathe.

4. Weakness, lethargy, and exercise intolerance – Tiring quickly on walks, reluctance to play.

5. Fainting episodes or collapse – Can occur with activity or excitement, caused by abnormal heart rhythm.

6. Weight loss – Especially with a normal or increased appetite.

7. Abdominal swelling – Due to fluid accumulation in the belly.

8. Pale gums – An indication of poor circulation.

9. Sudden death – Tragically, some dogs with DCM die suddenly before showing any signs. This is more common in Dobermans and Boxers.

If your dog has any of these symptoms, don‘t delay seeking veterinary care. Swift intervention is crucial to preserve heart function and quality of life. Treatment generally includes diuretics to reduce fluid buildup, ACE inhibitors and pimobendan to strengthen the heart muscle, and medications to control arrhythmias. Abdominocentesis (draining fluid from the belly) or even a ventilator may be needed in advanced cases.

Causes and Risk Factors

While the exact cause of primary DCM is unknown, genetics are thought to play a major role in the commonly affected breeds. Screening parents and siblings of affected dogs is important to reduce the incidence.

Some non-genetic factors have also been linked to DCM:

• Grain-free and exotic ingredient diets – In recent years, many cases of DCM have been tied to "BEG" diets (boutique, exotic protein, grain-free). Dogs eating these trendy diets showed low taurine levels and reversal of DCM when switched to a grain-inclusive diet. The FDA is still investigating the link.

• Chronic rapid heart rate – Conditions that cause a sustained fast heart rate, like untreated atrial fibrillation, can weaken the heart over time.

• Infections – Rarely, infections like Chagas disease or Bartonellosis can damage the heart muscle.

• Hypothyroidism – Low thyroid hormone can affect the heart muscle. Always screen for underlying diseases.

Prognosis: What to Expect

I wish I could sugarcoat this section, but the truth is, DCM is a progressive, incurable disease. While some dogs with occult DCM can remain stable for years with proper treatment, the long-term prognosis is generally poor once they develop signs of heart failure.

The median survival time after diagnosis is around 6-12 months, but this varies depending on the stage of disease and the individual dog. Some can live happily for 1-2 years with a good quality of life and dedicated care. Regular checkups and diligent home monitoring are a must to adjust medications and catch decompensation early.

As DCM advances, the muscle damage becomes irreversible and medications become less effective at controlling fluid buildup. Breathing often worsens, requiring higher oxygen levels to keep them comfortable.

It‘s important to work closely with your veterinarian to assess your dog‘s quality of life at each stage. I always encourage owners to talk openly about their goals and wishes early on, before a crisis arises. Having an end-of-life plan can reduce heartache and uncertainty when the time comes to say goodbye.

Prevention and Screening

While we can‘t change genetics, there are steps owners can take to reduce DCM risk:

1. Feed a high-quality, grain-inclusive diet from a reputable company that employs veterinary nutritionists and conducts feeding trials. Avoid fad diets and exotic proteins.

2. Keep your dog lean and active with regular age-appropriate exercise. Obesity strains the heart.

3. Test breeding dogs before mating and avoid carriers. Genetic tests are available for some at-risk breeds.

4. Start annual heart screenings by age 4 for predisposed breeds. Holter, echo, and cardiac biomarkers give the best chance of early detection.

5. Schedule twice yearly checkups with your vet and report any new symptoms promptly. A change in breathing, activity level, or appetite warrants investigation.

6. Consider taurine supplementation if your dog eats a grain-free or heavily plant-based diet. Discuss dosing with your vet.

The Future of DCM Research

Though we‘ve come a long way in understanding DCM, there are still many unanswered questions. Active areas of research include:

• Discovering causative genes to develop better screening tests for breeding dogs.

• Investigating the link between grain-free diets, taurine deficiency, and DCM.

• Exploring novel drug therapies to reverse or slow heart muscle damage.

• Developing more sensitive imaging and blood tests for earlier diagnosis.

• Studying the use of stem cells to regenerate damaged heart tissue.

Fortunately, there are many dedicated researchers and funding organizations working hard to improve the prevention, diagnosis, and treatment of this devastating disease. As both a veterinarian and dog owner, I‘m hopeful that continued research will lead to better outcomes for our beloved companions.

Coping With Your Dog‘s Diagnosis

Finally, I want to acknowledge the emotional toll a DCM diagnosis takes on owners. Hearing that your dog has a life-limiting illness is heartbreaking, especially when it seems to come out of nowhere. The rollercoaster of managing medications, monitoring breathing, and treasuring every day is exhausting.

Please know that you are not alone. Lean on your veterinary team for guidance and support. Talk openly with family and friends about what you‘re going through. Consider joining an online support group for owners of dogs with heart disease, like the DCM Dog Community on Facebook. Don‘t hesitate to seek counseling if you‘re struggling to cope.

Remember, every day you have with your dog is a gift. Take lots of pictures, make new memories, and spoil them rotten. love your dog enjoy every moment to have with them. When the sad day comes to say goodbye, know that you gave your dog the best life possible. They knew love every second they were with you.

In the fight against DCM, knowledge is power. I hope this article has armed you with the information you need to be a proactive advocate for your dog‘s heart health. Together, we can keep more tails wagging and hearts beating strong.