Dilated Cardiomyopathy in Dogs

What is DCM

If a beloved dog has been diagnosed with dilated cardiomyopathy (DCM), it can be difficult for the owner to accept. Dilated cardiomyopathy in dogs is a condition that affects the animal’s circulatory system and heart muscle, potentially leading to congestive heart failure. This condition is a leading cause of death among dogs in the United States. Heart disease is also a common cause of death in humans.

There are various conditions that commonly lead to death in dogs: viruses (such as Parvo and Distemper), cancer, and other diseases. People can exercise and take medications to lower their risk of heart disease, but identifying heart issues in dogs can be more challenging. Dog owners do their best to ensure their pets get enough exercise and eat properly, but this doesn’t guarantee immunity from heart diseases.

Manifestation of Dilated Cardiomyopathy in Dogs

DCM weakens the heart muscle in dogs, reducing the strength of its contractions and lowering its pumping ability. Essentially, the heart becomes enlarged and doesn’t function properly. Both the upper and lower chambers of the heart are affected, with one side often being more impacted than the other. This condition causes the heart chambers to enlarge, leading to congestive heart failure. Congestive heart failure occurs when the heart cannot pump enough blood, causing fluid pressure to increase and seep into the lungs or other areas. This fluid buildup around or within the lungs makes breathing difficult and limits oxygen flow into the bloodstream.

When congestive heart failure occurs, a dog may take short, rapid breaths to obtain enough oxygen. In humans, heart muscle issues are often the result of ischemic heart disease, which can cause a heart attack, but it’s different in animals. Sometimes, heart disease in dogs is genetic, while other times, it develops secondary to an infection.

Causes and Risk Factors of Dilated Cardiomyopathy

The exact cause of DCM is unknown, though genetics are believed to play a role. Most affected dogs are male, large-breed, and middle-aged, including Doberman Pinschers, Cocker Spaniels, Boxers, and Great Danes. DCM is rare in very young dogs. Dobermans and Portuguese Water Dogs are particularly susceptible compared to other breeds.

Symptoms of Dilated Cardiomyopathy in Dogs

Detecting DCM symptoms is challenging, making early identification difficult. There may be a reduced interest in physical activity. In some cases, a vet may detect a mild heart murmur during a routine exam. However, it’s important to note that a heart murmur isn’t a direct indication of DCM. As the disease progresses, such signs may become more noticeable. As DCM advances, the heart’s pumping ability decreases, blood pressure rises, and pressure is placed on veins and arteries around the heart, leading to fluid accumulation in the lungs and abdominal cavity. Together, these factors can result in heart failure, causing weakness, fainting, and even sudden death.



Clinical symptoms of DCM may include weakness, lethargy, rapid or abnormal breathing (tachypnea), exercise intolerance, coughing, loss of appetite, abdominal fluid buildup (ascites), and fainting (caused by insufficient blood flow to the brain).

Symptoms of Heart Failure in Dogs

As with heart failure in humans, the first signs often appear on the left side of the dog’s body due to the heart’s position. The left paw may become less mobile. Symptoms of heart failure in dogs also include a sharp decline in physical activity, rapid breathing, and light coughing. In some dogs, heart failure causes the abdomen to swell due to fluid buildup.

More severe symptoms of advanced heart failure include difficulty breathing, visible discomfort, worsening cough, inability to lie down, loss of appetite, and eventually, collapse. If a dog exhibits any of these symptoms, it should be taken to a veterinarian immediately to determine if heart failure is the cause. Unfortunately, severe heart failure can develop rapidly with this disease.

Diagnostic Methods for DCM

The vet will conduct an initial exam using an echocardiogram, which helps detect the primary indicator of DCM: an enlarged and weakening heart. An echocardiogram is combined with other tests to rule out false positives from other conditions, such as low thyroid levels, amino acid deficiencies, heart muscle inflammation, or reduced blood flow to the heart muscle. These conditions may show similar echocardiographic results.

Following this, the vet may perform an X-ray to identify an enlarged left ventricle and fluid in the lungs. They may also perform a DNA test (via cheek swab or blood sample) to identify known genetic mutations that cause DCM. An electrocardiogram (ECG) can detect arrhythmias and increased heart rate. Blood and urine tests may reveal liver and kidney issues that often arise due to heart problems.



For dogs of breeds with a known genetic predisposition to DCM, such as Boxers or Dobermans, the vet may recommend a 24-hour ECG monitoring test called a Holter monitor. This extended monitoring can help identify DCM at an early stage. An experienced vet can design the best course of treatment, and affected dogs should be removed from breeding programs to prevent passing on the disease.

Treatment of Dilated Cardiomyopathy in Dogs

Treatment for DCM focuses on improving heart function to delay disease progression. The vet may prescribe medications to enhance heart contractions and slow the heart rate, as well as other drugs to help manage the condition, including:

• Diuretics: Stimulate the kidneys to remove excess fluid from the body.
• ACE Inhibitors: Lower blood pressure and reduce resistance to blood flow from the heart. They are commonly used to treat heart disease in both humans and dogs, improving lifespan. Enalapril and benazepril are typically prescribed for dogs, though new drugs are continually being developed.
• Digitalis Glycosides: Improve heart function by reducing heart rate and strengthening contractions. Digoxin is the most common drug for dogs. Pets receiving this treatment should be monitored with blood tests and ECGs for potential toxic side effects.
• Vasodilators: Widen arteries or veins, reducing the heart’s workload. They are widely used in treating congestive heart failure related to DCM.
• Bronchodilators: Such as theophylline and aminophylline, help dogs breathe more easily when their heart and lungs are compromised.

Pimobendan is a newer class of drug for treating heart failure and DCM in dogs. Pimobendan is an inodilator (a combination of inotrope and vasodilator) and a calcium sensitizer that helps increase the heart’s pumping ability. None of these treatments require hospitalization and can be administered on an outpatient basis.

Prognosis of Dilated Cardiomyopathy in Dogs

Unfortunately, the prognosis for dogs with DCM is poor, as the disease progresses and eventually becomes fatal. Despite aggressive treatment, most dogs eventually die from the condition. However, dogs diagnosed early have a much better chance of controlling the disease and avoiding heart failure.

Most dogs with congestive heart failure die within 6 months, with the most severe cases living only a few weeks to months. Some dogs may live 1-2 years, and with early treatment before heart failure onset, they can lead a relatively normal life, though it may be shortened.

Different breeds respond differently to DCM. For example, Dobermans have a less favorable prognosis compared to other breeds, while DCM in Cocker Spaniels may progress relatively slowly. In the end, each case of this disease is unique.

Living with a Dog with DCM

After a DCM diagnosis, the primary goal is to ensure the dog’s comfort and closely monitor its condition. A professional vet will likely recommend follow-up visits every 3-6 months, depending on disease progression. If a dog is on medication for DCM, they will likely need to visit the vet every 10-14 days for blood tests, blood pressure checks, and/or heart rate assessments.

The owner should carefully monitor and record the dog’s breathing and sleep patterns to assist the vet in adjusting the treatment plan. If the DCM is advanced, including heart failure and/or abnormal heart rhythms, expect regular check-ups every 2-4 months and vigilant care for the pet’s well-being.