Around 1 in 10 dogs will develop heart disease in their lifetime, with the most common heart disease being mitral valve insufficiency. This leads to congestive heart failure.
A heart murmur is the abnormal sound of blood flowing back into the heart through leaky valves. When a veterinarian listens to your dog's heart, they should hear two parts of the heartbeat, the opening, and closing of the heart valves. When there is a backflow of blood from a leaky or damaged valve, a different sound is heard called a heart murmur. A heart murmur can be something that is detected early in life, such as at the puppy wellness checks, or later in life as your dog ages. Most heart murmurs are detected later in life.
Breeds commonly affected by heart murmurs include Cavalier King Charles Spaniels, Chihuahuas, Dachshunds, Dobermans, and Boxers.
What Causes Heart Murmurs in Dogs?
There are lots of reasons why your vet might be able to hear a heart murmur. Here are some of the most common causes:
Physiological or ‘Puppy Murmur’
The thickness or viscosity of a puppy's blood is different from an adult dog's. This, combined with the fact that the heart is growing rapidly, can lead to turbulent blood flow and a murmur. Puppy murmurs are usually quiet and disappear by six months of age. These physiological murmurs are innocent puppy murmurs and will not make your puppy unwell. It is important to follow up with your veterinarian as your puppy grows up to ensure the murmur goes away.
Leaky Heart Valves
There are two sets of atrioventricular valves that lie between the atria and the ventricles. They prevent blood from flowing back up into the atrium when the ventricle contracts. If they don’t form a good seal, blood leaks through the gaps. This jet stream of blood causes the murmuring sound. An example of this is Mitral Valve Disease (MVD), which is common in small breed dogs and particularly prominent in Cavalier King Charles Spaniels.
Birth Defects
If the heart and surrounding blood vessels don’t develop properly before birth, this can lead to a heart murmur. These congenital abnormalities could lead to extra blood vessels, a hole in the heart, or a narrowing of a blood vessel. Patent Ductus Arteriosus (PDA) is an example of an additional blood vessel. The ductus arteriosus is a vessel that bypasses the lungs when a puppy is in the womb. When the puppy is born, the vessel should close. However, occasionally it doesn’t.
Another example of a congenital condition is Pulmonic Stenosis, where the pulmonic valve forms a partial obstruction so that the blood cannot easily leave the heart to go to the lungs. These conditions can be very serious, and without prompt treatment, can be life-threatening.
Changes in the Size of the Heart
If the heart becomes enlarged, the blood flow becomes more turbulent and less smooth. This can lead to murmurs, although it doesn’t always. Dilated Cardiomyopathy (DCM) in dogs causes enlargement of the heart and thinning of the muscular walls. This condition is common in Dobermans and Cocker Spaniels, among other breeds, and sadly can be fatal. It’s important to remember though that DCM doesn’t always cause a heart murmur, so dog breeds who are predisposed should be screened for the condition.
Signs and Symptoms of Heart Murmurs in Dogs
Heart murmurs in dogs are a common cardiac problem that is caused by turbulent blood flow in the heart. Heart murmurs can be a sign of an underlying condition, such as heart valve disease, congenital heart defects, or dilated cardiomyopathy. Identifying the symptoms of heart murmurs is crucial to the early detection and treatment of any potential cardiac issues.
When the heart murmur is severe, common signs we see in dogs include:
- Abnormal or racing heartbeat
- Difficulty breathing or shortness of breath
- Excessive panting, even when resting
- Coughing, especially at night or after exercise
- Fatigue or weakness
- Fainting or collapsing
- Exercise intolerance
- Blue or gray tinge to the gums (emergency)
- Lack of appetite
- Severe water retention
1. Have you noticed changes in your pet’s appetite or thirst?
2. Have you noticed changes in your pet’s elimination patterns (pottying habits)?
3. Has your pet vomited more than once in 24 hours?
4. Is there a change in your pet’s breathing?
5. Is your pet pacing and unable to settle?
6. Is your pet panting more than usual?
7. Is your pet drooling more than usual?
8. Are there changes to your pet’s eyes?
9. Is your pet whining or vocalizing more than usual?
10. Is your pet shaking more than usual?
11. Is your pet hiding or avoiding physical contact more than usual?
12. Is your pet more lethargic and sleeping more than usual?
13. Does your pet have a cough?
14. Are you concerned about changes in your pet’s behavior?
15. Have you noticed a new bump or growth on your pet?
16. Has your pet eaten something that could be toxic or a foreign object?
17. Has your pet experienced a seizure?
18. Is your pet having a hard time moving around?
19. Does your pet have a distended (bloated belly)?
20. Does your pet have a wound or injury?
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Should My Pet Be Seen by a Veterinarian?
1. Have you noticed changes in your pet’s appetite or thirst?
2. Have you noticed changes in your pet’s elimination patterns (pottying habits)?
3. Has your pet vomited more than once in 24 hours?
4. Is there a change in your pet’s breathing?
5. Is your pet pacing and unable to settle?
6. Is your pet panting more than usual?
7. Is your pet drooling more than usual?
8. Are there changes to your pet’s eyes?
9. Is your pet whining or vocalizing more than usual?
10. Is your pet shaking more than usual?
11. Is your pet hiding or avoiding physical contact more than usual?
12. Is your pet more lethargic and sleeping more than usual?
13. Does your pet have a cough?
14. Are you concerned about changes in your pet’s behavior?
15. Have you noticed a new bump or growth on your pet?
16. Has your pet eaten something that could be toxic or a foreign object?
17. Has your pet experienced a seizure?
18. Is your pet having a hard time moving around?
19. Does your pet have a distended (bloated belly)?
20. Does your pet have a wound or injury?
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How Are Heart Murmurs Diagnosed in Dogs?
Heart murmurs in dogs are first picked up when your veterinarian listens to your dog’s chest with a stethoscope. A heart murmur is graded on a scale of one to six, one being very mild and six very severe.
Low-grade heart murmurs may be monitored by your veterinarian with regular checkups every three to six months. The veterinarian will listen to the heart again at this point and if the heart murmur is getting worse, then diagnostic tests may be advised.
Diagnostic tests to find out more information about your dog’s heart murmurs often start with echocardiography, which is an ultrasound of the heart. This is best done by a board-certified veterinary cardiologist if there is one available in your area. The cardiologist will take measurements of the heart and look at the flow of blood through the heart. These measurements tell us how advanced your dog’s heart disease is. Medication can be prescribed to help support the heart based on these findings.
Chest X-rays may be taken alongside the echocardiography exam. This helps the veterinarian to see signs of congestive heart failure such as fluid accumulation in the lungs, or enlargement of your dog's heart.
Further tests that may be run include electrocardiograms (ECG) which measure the electrical activity of the heart and blood tests to look for other medical conditions that can be treated to help the overall health of the heart.
How Are Heart Murmurs Treated?
The treatment for some grades of heart murmurs may be just to monitor them if your dog is showing no obvious signs of illness associated with the heart murmur.
If your puppy has a congenital heart abnormality, such as a PDA, veterinary surgery may be needed to fix the problem.
Dogs who have heart murmurs related to congestive heart failure need medications to support the heart. These medications help the heart to pump blood around the body and reduce fluid build-up in the lungs. This helps your dog’s overall quality of life. Medications will need to be given daily, and often the doses of medications will need to be increased as your dog’s condition gets more advanced.
Frequently Asked Questions
Is a heart murmur painful?
A heart murmur in itself is not painful, but the effects of having a severe heart murmur such as pulmonary edema (fluid on the lungs) can be stressful, which is a similar sensation to pain.
When should I worry about my dog having a heart murmur?
A heart murmur doesn’t mean that your dog has heart failure, nor does it mean that they’ll develop heart failure soon. What’s most important is that it is monitored closely by your vet and that you know what symptoms to watch out for.
What are the remedies for dog heart murmurs?
While there is no cure for a heart murmur in dogs, treatment can help manage the symptoms. Depending on the severity, remedies may include a change in diet, exercise restrictions, and medication to manage the underlying condition causing the murmur.
Can my dog still exercise regularly with a heart murmur?
The severity of the heart murmur dictates how much exercise is okay for your dog. For low-grade heart murmurs, exercise can continue as normal. For high-grade heart murmurs and dogs with congestive heart failure, gentle short walks only are advised.
Can a dog live with a heart murmur for a long time?
The prognosis for a heart murmur will vary depending on the cause. Many birth defects can become fatal without treatment. However, heart murmurs in adult dogs can remain stable without treatment for years before congestive heart failure begins.
Acquired conditions like MVD can be managed with diuretics and other medications to control your dog’s blood pressure and help the heart pump more effectively. While these sadly won’t work forever, they can give you many months or even years with your canine companion.
What can I do at home to help my dog with a heart murmur?
The best thing you can do for your dog at home is to keep its body weight within a normal range. Extra weight carried by your dog puts extra pressure on their joints, heart, and overall health. Talk to your veterinarian about a weight loss diet if you think your dog is overweight.
Summary
A heart murmur can go undetected for many years and cause your dog no issues. With high numbers of dogs suffering from heart disease at some point in their life, it’s worth keeping an eye out for heart disease early on in their life through regular health checks with your veterinarian. This means medications can be started sooner, which slows down the progression of the heart disease and prolongs the time that your dog has left to enjoy with you.
Keeping your dog healthy, and fit, and not letting your dog get overweight will improve heart health. If you would like more advice on how to do this or anything else covered in this article, talk to our BetterVet veterinarian today.
