Our dog’s hearts are vital for their good health, so finding out that your dog may have an enlarged heart can be very worrying. Several different health conditions can cause an enlarged heart in dogs, and it’s essential to diagnose the exact problem so that your pet can get the treatment they need. 

Key Takeaways:

  • Enlarged heart in dogs, or cardiomegaly, is when the heart becomes abnormally larger due to an underlying cardiac issue.
  • Treatment includes medication like Pimobendan and, in some cases, surgery.
  • Early diagnosis and proper treatment are crucial for improving the dog's quality of life.

What is an Enlarged Heart in Dogs?

An enlarged heart in dogs, known as cardiomegaly, is when the heart grows beyond its normal size due to an underlying heart condition. This enlargement is usually a result of an underlying cardiac disease or condition that affects the heart's structure or function. When the heart enlarges, it compromises its ability to pump blood and perform its essential functions efficiently.

What Causes an Enlarged Heart in Dogs?

Two common causes of an enlarged heart in adult dogs are mitral valve disease and dilated cardiomyopathy. These illnesses are rare in puppies, but other congenital conditions (ones that a puppy is born with) can cause an enlarged heart at a young age.  

Mitral Valve Disease (MVD)

Mitral Valve Disease (MVD) is a heart condition that can cause the heart to enlarge. It happens when the mitral valve, which directs blood flow in the heart, thickens and stiffens with age. This can lead to leaks, making it harder for the heart to pump blood effectively.

MVD is more common in smaller breeds and cross-breeds under 44 pounds, and it's often seen in older dogs. However, middle-aged dogs can also be affected, especially certain breeds.

Specific breeds at higher risk of Mitral Valve Disease include:

Dilated Cardiomyopathy (DCM)

Dilated Cardiomyopathy (DCM) directly affects the muscles of the heart, causing them to become thinner and weaker. This means the heart cannot pump blood around the body as effectively. As the muscles of the heart weaken, more and more blood is left behind when the heart tries to pump it out, causing the heart muscle to be stretched and the heart to enlarge. 

DCM mainly affects large pure-breed dogs, and the risk is thought to be genetic. This means that if a dog has a sibling or parent who develops DCM at some point in their life, they are also at a high risk of developing this illness.

Breeds at high risk of DCM include:

  • Great Danes
  • Dobermanns
  • Boxers
  • Newfoundlands
  • Irish Wolfhounds
  • Deerhounds

Congenital Heart Conditions

There are many different heart conditions that a puppy can be born with. These are all rare, but most of them will lead to an enlarged heart over time if they are severe. Some conditions can cause heart enlargement as a puppy or become an issue later into adulthood.

Examples include:

  • Patent Ductus Arteriosus (PDA)
  • Ventricular or Atrial Septal Defect (a hole in the heart)
  • Aortic or Pulmonic Stenosis (narrowing of valves)
  • Mitral or Tricuspid Dysplasia (valves that have not properly formed)

Signs & Symptoms of an Enlarged Heart in Dogs

In the early stages, there are often no obvious symptoms that a dog has an enlarged heart. Your vet might hear a heart murmur or an irregular heartbeat, but in some cases (particularly with DCM), the dog’s heart may sound normal. 

In the later stages, when the heart is having difficulty coping, there may be more obvious symptoms. These include:

Should My Pet Be Seen by a Veterinarian?

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Should My Pet Be Seen by a Veterinarian?
1. Have you noticed changes in your pet’s appetite?
2. Does your pet have diarrhea or loose stools?
3. Have you noticed changes in your pet’s thirst/water consumption?
4. Is your pet having accidents in the house?
5. Is your pet pacing and unable to settle?
6. Is your pet panting more than usual?
7. Is your pet whining or vocalizing more than usual?
8. Is your pet shaking more than usual?
9. Is your pet hiding or avoiding physical contact more than usual?
10. Is your pet more lethargic and sleeping more than usual?
11. Are you concerned about changes in your pet’s behavior?
12. Is your pet scratching their ears?
13. Is your pet licking their paws more than usual?
14. Does your pet have a rash?
15. Is your pet moving more slowly than usual or having a harder time getting up or down?

Should My Pet Be Seen by a Veterinarian?

1. Have you noticed changes in your pet’s appetite?
2. Does your pet have diarrhea or loose stools?
3. Have you noticed changes in your pet’s thirst/water consumption?
4. Is your pet having accidents in the house?
5. Is your pet pacing and unable to settle?
6. Is your pet panting more than usual?
7. Is your pet whining or vocalizing more than usual?
8. Is your pet shaking more than usual?
9. Is your pet hiding or avoiding physical contact more than usual?
10. Is your pet more lethargic and sleeping more than usual?
11. Are you concerned about changes in your pet’s behavior?
12. Is your pet scratching their ears?
13. Is your pet licking their paws more than usual?
14. Does your pet have a rash?
15. Is your pet moving more slowly than usual or having a harder time getting up or down?
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Diagnosing an Enlarged Heart in Dogs

Your vet may suspect that your dog has an enlarged heart when they listen with a stethoscope during a routine wellness checkup. However, it is not possible to diagnose the problem just by listening. Tests that your vet may recommend running include:

Blood Tests

Your vet may recommend running general blood tests to check for any other cause of your dog’s symptoms. Some specific blood tests can help to measure heart health, including Pro-BNP and Cardiac Troponins. However, these tests are usually insufficient to diagnose a problem.

X-Rays

The outline of the heart can usually be seen easily on X-rays, and your vet can measure this to look for signs that a dog’s heart is enlarged. They can also look for other signs that the dog’s heart is struggling, such as enlarged blood vessels or lung fluid.

Echocardiography 

This advanced diagnostic technique uses an ultrasound scan to observe the heart as it beats. It enables the vet to measure the chambers' size, detect any enlargement, and assess the internal structure of the heart to identify the exact cause of the enlargement. Most heart conditions require a comprehensive heart scan performed by a veterinary cardiologist.

Electrocardiography (ECG)

An electrocardiogram (ECG) measures the heart's electrical activity and is crucial for dogs with irregular heartbeats. It provides valuable insights into the underlying cause of the irregular beat and helps determine the most appropriate treatment. ECG is also used to monitor the dog's response to treatment.

Shorter ECG measurements can be done at home or in the clinic using clip-on electrical leads. In some cases, dogs may need to be monitored for several days using a Holter monitor, which is a wearable ECG device.

Treatment for Dogs with an Enlarged Heart

Treating dogs with an enlarged heart include medication like Pimobendan & in some cases surgery. Here's a breakdown of each treatment option:

Medication

Once dogs show symptoms of an enlarged heart, they will need medication to relieve their discomfort and improve their quality of life. Regular checkups are necessary to adjust the medication as the condition progresses. Pimobendan is a medication that helps strengthen the heart's contractions and has been shown to delay heart failure in dogs with Mitral Valve Disease or DCM. Giving this medication to dogs before they display symptoms can also be beneficial.

Surgery

Certain heart conditions can be treated with surgery. For example, Patent Ductus Arteriosus (PDA) is a congenital heart disease where a blood vessel remains open after birth when it should close. Surgical intervention to close the vessel may be an option if the condition is not too advanced. In some cases, replacing a leaky valve, a procedure performed in humans with Mitral Valve Disease can also be done in dogs. However, it is a complex procedure available only in limited locations. Minimally invasive techniques that directly alter the heart without surgery can help dogs with PDAs or pulmonic stenosis.

It's important to note that dogs of any size and age can develop an enlarged heart. In the early stages, there may be few external signs. If a veterinarian detects a heart murmur or suspects a heart problem, running tests to determine the treatment needed is crucial for your dog's well-being.

Conclusion

In summary, an enlarged heart in dogs can be a concerning condition with various underlying causes. If you notice any signs or symptoms such as reluctance to exercise, rapid breathing, coughing, or weight loss, it's crucial to consult a veterinarian. Early diagnosis and proper treatment are vital to improving your dog's quality of life.

Don't hesitate to book a visit with a vet if you suspect your dog may have an enlarged heart. Your veterinarian can provide the necessary tests and guidance to ensure your dog receives the appropriate care.

Frequently Asked Questions

What is the life expectancy of a dog with an enlarged heart?

The life expectancy of a dog with an enlarged heart varies based on the underlying condition and treatment. 

Is exercise good for dogs with enlarged hearts?

Exercise should be moderated for dogs with enlarged hearts. Consult your vet for a tailored exercise plan that suits your dog's condition, as excessive or strenuous activity may worsen their symptoms.

Do dogs with enlarged hearts suffer?

Dogs with enlarged hearts may experience discomfort and reduced quality of life. Timely diagnosis, medication, and veterinary care can help alleviate symptoms and improve their overall well-being.

Can an enlarged heart go back to normal in dogs?

An enlarged heart in dogs generally cannot return to normal size. Treatment aims to manage symptoms and slow progression, not reverse enlargement. Early diagnosis and proper care are crucial for improving a dog's quality of life.