Congestive Heart Failure in Dogs: Symptoms, Causes, and Management

Congestive heart failure (CHF) in dogs occurs when the heart cannot pump blood efficiently, causing fluid to build up in the lungs, abdomen, or other parts of the body. 

Dogs with CHF may develop coughing, difficulty breathing, weakness, exercise intolerance, or a swollen abdomen.

Congestive heart failure requires veterinary treatment and ongoing management. Dogs experiencing respiratory distress or trouble breathing need immediate emergency veterinary care.

What is Congestive Heart Failure in Dogs?

Congestive heart failure in dogs is a condition in which fluid builds up because the heart can't pump blood efficiently throughout the body.

A damaged heart may struggle to pump blood, causing blood to back up and fluid to accumulate in the chest, abdomen, or both, depending on the type of CHF.

A dog's heart has a right and left side. The right side receives oxygen-poor blood from the body and transports it to the lungs, where it receives oxygen. The left side pumps oxygen-rich blood back out to the body to nourish the tissues.

There are two types of CHF in dogs:

• Left-sided CHF: This is the more common type in dogs. Blood backs up in the lungs, causing fluid to accumulate in the lungs (pulmonary edema). Dogs with left-sided CHF will usually have a cough and difficulty breathing.
• Right-sided CHF: Blood backs up throughout the body's circulatory system, causing fluid to accumulate in the abdomen (ascites) and/or limbs (peripheral edema). 

Stages of Congestive Heart Failure in Dogs

Congestive heart failure in dogs is classified in stages based on risk, structural heart changes, symptoms, and response to treatment. 

The stages progress from Stage A, when a dog is at risk but has no symptoms, to Stage D, when severe symptoms no longer respond to treatment.

• Stage A: Dogs are at higher risk for developing CHF but have no symptoms or structural changes to the heart. Dogs with a genetic risk include small breeds such as Miniature Poodles, Cocker Spaniels, and Terrier breeds, as well as some larger breeds such as Great Danes and Dobermans.
• Stage B: Dogs have a heart murmur—a "whooshing" or "swishing" sound a veterinarian can hear—but no symptoms. A murmur indicates turbulent blood flow within the heart.
• Stage B2: Dogs have structural changes visible on an X-ray/radiograph or echocardiogram (a specialized ultrasound used to diagnose the heart) but do not have symptoms.
• Stage C: Dogs have current or previous clinical signs of congestive heart failure but still respond positively to medications and treatments such as supplemental oxygen.
• Stage D: This is considered "end-stage" disease. Dogs typically have severe symptoms that no longer respond to medications or other treatments.

What Are the Symptoms of Congestive Heart Failure in Dogs?

Symptoms of congestive heart failure in dogs can include coughing, difficulty breathing, an increased breathing rate at rest, exercise intolerance, fatigue or weakness, blue gums, a distended abdomen, and collapse.

Signs of CHF in dogs may include:

• Coughing, sometimes even coughing up foam

• Difficulty breathing

• Increased rate of breathing, even when resting

• Inability to exercise

• Fatigue, lethargy, and weakness

• Cyanotic (blue) gums

• Distended abdomen

• Collapse or sudden death

Seek an emergency veterinarian immediately if your dog has any signs of respiratory distress or trouble breathing. Dogs experiencing moderate to severe signs of congestive heart failure may require hospitalization and immediate care.

What Causes Congestive Heart Failure in Dogs?

There are many possible causes of congestive heart failure in dogs, but the most common is myxomatous mitral valve disease (MMVD), also called chronic mitral valve disease, degenerative mitral valve disease, mitral insufficiency, or endocardiosis.

Myxomatous mitral valve disease (MMVD): The mitral valve, also known as the bicuspid or left atrioventricular valve, is on the left side of the heart and acts as the doorway between the left atrium and left ventricle.

MMVD occurs when this valve fails to close, causing blood to leak through it. Over time, MMVD can result in left-sided congestive heart failure due to a decreased ability of the left side of the heart to pump oxygen-rich blood to the body.

The cause of mitral valve disease is unknown, but there appears to be a strong genetic component. Many small-breed dogs have a genetic predisposition to mitral valve disease.

Dilated cardiomyopathy (DCM): In large-breed dogs, the most common inherited form of heart disease is DCM. The heart muscle becomes weak and is unable to properly contract, causing the heart to dilate.

Dogs predisposed to DCM include Doberman Pinschers, Boxers, and Great Danes.

Other causes of CHF in dogs include:

• Heart valve disease
• Defects or holes in the walls of the heart (ventricular septal defect)
• Congenital cardiac defects, including patent ductus arteriosus, pulmonic stenosis, and aortic stenosis
• Accumulation of fluid in the sac around the heart (pericardial effusion)
• Heartworm disease
• Arrhythmias (irregular heartbeat)
• Increased blood pressure
• Infection (endocarditis)
• Tumors

How Is Congestive Heart Failure in Dogs Diagnosed?

Veterinarians diagnose congestive heart failure in dogs by listening to the heart and lungs and may use chest X-rays, an electrocardiogram (ECG or EKG), and an echocardiogram to evaluate the heart and look for signs of CHF.

Diagnosis starts with listening to your dog's heart and lungs with a stethoscope. Most dogs will have a heart murmur, which is graded in severity from 1 to 6:

• Grade 1: Very soft murmur, often difficult to hear
• Grade 2: Soft murmur but readily heard
• Grade 3: Moderately loud murmur
• Grade 4: Loud murmur
• Grade 5: Very loud murmur that can be heard with the stethoscope barely touching the chest. The veterinarian can feel a vibration through the chest wall over the heart (palpable thrill).
• Grade 6: Very loud murmur that can be heard with the stethoscope held over the chest without touching the skin. The veterinarian can feel a vibration through the chest wall over the heart (palpable thrill).

Chest X-rays: If your veterinarian suspects CHF, they will likely perform a chest X-ray or radiograph to look for heart enlargement or evidence of fluid in the lungs (pulmonary edema).

Electrocardiogram (ECG or EKG): This test may be used to assess the rate and rhythm of your dog's heart.

Echocardiogram: Your veterinarian may refer you to a veterinary cardiologist for specialized testing such as an echocardiogram, or ultrasound of the heart.

An echocardiogram is the most useful tool for identifying the source of a murmur, the likely cause of CHF, and measuring the heart's ability to pump blood.

How Is Congestive Heart Failure in Dogs Treated?

Treatment for congestive heart failure in dogs may include medications, oxygen therapy, and nutritional management, along with treatment of the underlying heart disease when possible.

Your veterinarian will likely recommend treating both the underlying heart disease, if possible, and any fluid accumulation.

An underlying cause such as heartworm disease may be treatable, but in most cases the cause of congestive heart failure in dogs cannot be cured and can only be managed.

Medications for CHF in Dogs

Medications used to treat CHF in dogs depend on the underlying cause and severity. Your veterinarian or veterinary cardiologist will determine the appropriate medications, dosages, and frequency and should be consulted before any changes are made.

Diuretics: Diuretics such as furosemide are typically a mainstay of medical treatment for congestive heart failure. They decrease fluid accumulation in the lungs, abdomen, or legs, depending on the cause of heart failure.

Pimobendan: Pimobendan is another commonly used medication for CHF. It improves the heart's ability to contract, increases pumping action, opens blood vessels, and reduces the amount of work the heart has to perform.

For myxomatous mitral valve disease and dilated cardiomyopathy, pimobendan has been shown to delay the onset of heart failure and increase overall survival time when started at a certain stage before symptoms appear (Stage B2).

Other medications that may be used for CHF include:

• Digoxin 

• Diltiazem 

• Benazepril  

• Enalapril 

• Propranolol  

• Atenolol  

• Amlodipine 

Your dog will likely receive a combination of medications tailored by your veterinarian to address their specific CHF and underlying heart disease.

Oxygen Therapy for CHF in Dogs

Dogs with left-sided heart failure or significant fluid in the lungs may need supplemental oxygen if they cannot get enough oxygen from their lungs into their bloodstream.

Oxygen may be provided through:

• An oxygen cage
• A tube through the nose
• Direct airflow toward the face ("flow-by" oxygen)

In severe cases, a dog may need to be intubated to receive oxygen or require mechanical ventilation. According to the supplied article, this is typically associated with a poor prognosis.

Nutrition for Congestive Heart Failure in Dogs

Nutritional management may be used alongside medical treatment for congestive heart failure. Nutrition tailored to your dog's underlying heart condition may help slow the progression of heart disease and improve quality of life.

Diet recommendations and supplements should always be discussed with your primary veterinarian, veterinary cardiologist, or veterinary nutritionist. Your veterinarian may recommend a food tailored toward heart health.

Specific supplements such as fish oil/omega fatty acids, taurine, and L-carnitine may be considered to decrease inflammation, help manage arrhythmias, and improve heart function.

Other recommendations may include weight management, maintaining muscle mass, and eating a balanced diet. Consult your veterinarian, cardiologist, or veterinary nutritionist before making diet changes or adding supplements.

How To Manage Congestive Heart Failure in Dogs

Management of congestive heart failure in dogs depends on the underlying cause and should be tailored to your dog by your veterinarian or veterinary cardiologist.

With diligent management and daily medications, dogs with CHF can have a good quality of life and may have an extended survival time.

Most dogs will be able to enjoy a moderate level of exercise and activity without strict restrictions.

Monitoring Your Dog's Respiratory Rate

An important part of at-home care for dogs with left-sided congestive heart failure is monitoring their resting respiratory rate, or the number of breaths they take per minute. 

Respiratory rate can indicate the degree of fluid accumulation in the lungs and help determine whether you need to contact your veterinarian.

As a rule of thumb, a dog at rest should have a respiratory rate of less than 30 breaths per minute.

When measuring your dog's respiratory rate:

• Count one breath as one complete breath in and out.
• Count while your dog is resting or sleeping.
• Do not count immediately after physical activity.

Veterinary Monitoring

Your veterinarian may perform periodic chest X-rays to assess heart size and look for evidence of fluid in the lungs.

Blood work, including kidney values and electrolytes, will likely be recommended every three to six months to ensure your dog is tolerating their heart medication.

Your veterinary cardiologist will likely recheck an echocardiogram every six to 12 months to assess changes in the heart and adjust medication as needed.

Long-Term Management

There is no cure for congestive heart failure in dogs, but diligent management and daily medications can help your dog maintain a good quality of life and may extend survival time.

However, once Stage D congestive heart failure develops, the median life range is nine months.