Heart disease in dogs is quite common, affecting 10% of all dogs and up to 35% of dogs over 13 years old. Most cases develop with age (not from birth defects). Of these, 75% have mitral valve disease (MVD), 10% have dilated cardiomyopathy (DCM), and 15% have other conditions such as heartworm disease or inherited heart defects.

MVD is common in older Cavalier King Charles Spaniels.

Mitral Valve Disease (MVD)

Mitral Valve Disease occurs when a heart valve weakens, allowing blood to leak when the heart contracts. MVD is most common in older, small-breed dogs. In fact, 30% of small-breed dogs over 10 years old have MVD. It often progresses slowly, which allows us the opportunity to significantly slow the disease and improve the quality and quantity of life.

Dilated Cardiomyopathy (DCM)

Dilated Cardiomyopathy is a problem with the heart muscle itself and usually affects middle-aged large-breed dogs like Dobermans, Boxers, Great Danes, Newfoundlands, and Cocker Spaniels. A juvenile form can also affect adolescent Portuguese Water Dogs. These dogs have a stretched, weak heart muscle, leading to inefficient blood pumping. DCM often progresses rapidly.

Boxer is a breed that is affected by DCM.

Symptoms of Heart Disease

Heart disease symptoms typically appear when it progresses to congestive heart failure (CHF). Symptoms may include:

• Weight loss
• Weakness
• Exercise intolerance
• Low body temperature and cold limbs
• Rapid breathing or difficulty breathing
• Wet cough

Testing and Treatment Recommendations Based on Heart Disease Stage:

Stage A

Dogs with currently normal hearts but a high risk of heart disease (e.g., all healthy Cavalier King Charles Spaniels are considered Stage A).

• Dogs with currently normal hearts but a high risk of heart disease (e.g., all healthy Cavalier King Charles Spaniels are considered Stage A).
• Annual exams are recommended to check for heart murmurs, especially in small breeds prone to MVD (such as Cavalier King Charles Spaniels, Dachshunds, Miniature, and Toy Poodles).
• No specific treatments are needed at this stage.

Stage B

There is evidence of structural heart changes (usually a murmur), but no symptoms are present.

• There is evidence of structural heart changes (usually a murmur) but no symptoms.
• Chest X-rays are needed to establish baseline measurements of the heart.
• Blood pressure checks and baseline lab work (red blood cell count, protein levels, kidney values, and urinalysis) are recommended annually.
• An echocardiogram (ultrasound of the heart) is ideal for diagnosing the cause of the murmur, identifying the current stage/substage, and guiding optimal long-term management.
• If an echocardiogram is unavailable, the proBNP blood test can screen for heart muscle strain and predict when heart failure may occur.

Home Monitoring

• Resting or sleeping respiratory rate should be checked weekly. If your dog’s respiratory rate exceeds 30 breaths per minute (or 15 breaths per 30 seconds) for three consecutive days, please see your vet promptly. Respiratory rates can be logged on paper, or the is a useful option.
• Also, please bring your dog in for a recheck if you notice reduced activity or coughing.

Substage B1: 

There are no changes visible on chest x-rays or echocardiogram.

• No medications are indicated
• Nutritional goals: optimize body weight and muscle mass, avoid excess calorie intake or nutritional deficiencies. Annual chest X-rays are recommended.
• Assess resting respiratory rate when your dog is soundly sleeping frequently enough to know what’s normal for him or her (every 1-2 weeks may be adequate).

Substage B2:

There are abnormal findings on X-rays or echocardiogram (usually heart enlargement). The average time before progression to congestive heart failure (Stage C) is 2 to 3.5 years for dogs with Stage B2 MVD.

• Vetmedin delays the onset of heart failure by an average of 15 months when started in Stage B2 MVD, providing 60% more time before symptoms develop.
• Mild sodium restriction and maintaining an ideal body condition are recommended.
• X-rays and blood pressure should be monitored every 6 months. 
• Monitor resting respiratory rate when soundly sleeping at least weekly. 

Stage C

The patient has current or previous congestive heart failure (CHF) symptoms, such as reduced activity, increased respiratory rate, panting, exercise intolerance, or coughing.

• Chest X-rays, blood pressure measurements, and lab work are needed every 3-6 months. Referral to a cardiologist for further testing, including an echocardiogram, is ideal.
• Most dogs with Stage C MVD do best when treated with “Quad Therapy”
  • Vetmedin improves heart chamber filling and contractions.
  • Salix (diuretic) helps remove retained fluid
  • ACE inhibitors (Benazepril, Enalapril) reduce blood vessel constriction.
  • Spironolactone (another diuretic) targets different receptors to improve symptom control and survival
• Goals
  • Improve breathing
  • Reduce fluid accumulation
  • Boost energy
  • Maintain appetite
  • Reduce emergency visits.
• X-rays and lab work should be checked 10-14 days after starting medication to monitor progress and screen for side effects.
• Dietary Changes
  • Maintain calorie intake to prevent muscle loss, avoid low-protein diets (kidney diets, many senior diets).
  • A low-sodium diet is indicated.
  • Potassium supplementation may be needed.
  • Omega-3 fatty acid supplementation may be useful. Taurine, L-carnitine, or CoQ10 might be beneficial.

Home Care

• Monitor appetite and body condition closely. If your dog loses weight or appetite, or if the respiratory rate exceeds 30-35 breaths per minute for three consecutive days, see your vet.
• Encourage exercise as tolerated, but avoid prolonged strenuous activity.

The average survival time for Stage C MVD is about 1 year, though some dogs live longer.

Stage D

This stage indicates life-threatening heart failure that no longer responds to routine medications. Aggressive care is required, and the patient may be nearing the end of life.

• Referral to a cardiologist is ideal. Higher-level testing can help guide treatment.
• Medications are often maximized or swapped (e.g., Torsemide instead of Furosemide).
• Monitoring appetite, body condition, and breathing is critical. Blue gums, inability to breathe, or fluid from the nose require emergency care.
• Quality of life should be evaluated. If your pet can no longer enjoy favorite activities, sleep comfortably, or breathe easily, humane euthanasia may be considered to prevent suffering.

Important contacts

Animal Care Clinic: (417) 334-7696

Emergency Veterinary Clinic: (417) 890-1600

University of Missouri Veterinary Health Center (Cardiology referral): (573) 882-7821

Additional resources

• Heart health tracking on the
• Accurate client handouts on common medications and monitoring resting respiratory rates.
• Optimizing nutrition for pets with heart disease
• Tons of accurate articles on various pet health topics can be found at pethealthnetwork.com.

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