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PetMD.com explains, “Murmurs are extra heart vibrations that are produced as a result of a disturbance in the blood flow — enough, in fact, to produce audible noise. Often, the murmurs are classified according to a variety of characteristics, including their timing. Systolic murmurs, for example, occur when the heart muscle contracts; diastolic murmurs occur when the heart muscle relaxes between beats; and continuous and to-and-fro murmurs occur throughout all or most of the cardiac cycle.”
According to petplace.com, “Heart murmurs may affect dogs of any age or sex. They may also affect any breed, however some breeds are more prone to heart disease. Some murmurs heard in puppies and kittens will disappear as the pet ages (usually < 4 months).”
What Can Cause a Heart Murmur?
According to PetMD.com, murmurs are caused by the following:
- Disturbed blood flow associated with high flow through normal or abnormal valves or with structures vibrating in the blood flow.
- Flow disturbances associated with outflow obstruction or forward flow through diseased valves or into a dilated great vessel.
- Flow disturbances associated with regurgitant flow due to an incompetent valve, patent ductus arteriosus, or a defect in the septum (the wall that separates the heart’s left and right sides).
Here are some the underlying conditions and diseases that may bring on murmurs:
- Heartworm disease
- Mitral and tricuspid valve heart failure
- Cardiomyopathy and aortic valve insufficiency
- Mitral and tricuspid valve dysplasia
- Systolic anterior mitral motion (SAM)
- Dynamic right ventricular outflow obstruction
- Dynamic subaortic stenosis
- Aortic stenosis
- Pulmonic stenosis
- Atrial and ventricular septal defect
- Tetralogy of Fallot
- Mitral and tricuspid valve endocarditis (inflammation of the inner part of the heart)
Continuous or To-and-Fro Murmurs
- Patent ductus arteriosus
- Ventricular septal defect with aortic regurgitation
- Aortic stenosis with aortic regurgitation
- Mitral and tricuspid valve stenosis
- Aortic and pulmonic valve endocarditis (inflammation of the inner layer of the heart)
What are the Symptoms of a Heart Murmur?
“The symptoms associated with murmurs depend on a variety of characteristics, including their grade, configuration, and location. If, however, the murmur is associated with structural heart disease, your dog may display signs of congestive heart failure such as coughing, weakness, or exercise intolerance,” advises PetMD.com.
Grading Scale for Murmurs
- Grade I—barely audible
- Grade II—soft, but easily heard with a stethoscope
- Grade III—intermediate loudness; most murmurs which are related to the mechanics of blood circulation are at least grade III
- Grade IV—loud murmur that radiates widely, often including opposite side of chest
- Grade V—very loud, audible with stethoscope barely touching the chest; the vibration is also strong enough to be felt through the animal’s chest wall
- Grade VI—very loud, audible with stethoscope barely touching the chest; the vibration is also strong enough to be felt through the animal’s chest wall
“If you notice that your dog’s tongue or gums has turned to a blue color, seek help immediately. This is a sign that your dog is not circulating the required amount of blood for his body systems to function correctly and can be a dangerous indication,” warns vetinfo.com.
How is a Heart Murmur Diagnosed?
You will need to give your veterinarian a thorough history of your dog’s health, including the onset and nature of the symptoms.
Petplace.com explains, “When a murmur is present, the goal is to determine the underlying cause for the murmur. Tests may include urinalysis, chest radiographs [X-rays] and an echocardiogram.”
Your vet may also recommend your dog gets Doppler studies and a complete blood count to help confirm any anemic murmurs.
How is a Heart Murmur Treated?
Because there are so many underlying issues that can cause a murmur, treatment truly depends on what is causing the murmur to develop in the first place.
According to PetMD.com, “Unless heart failure is evident, your dog will be treated as an outpatient. The course of treatment will be determined based on the associated clinical signs. Puppies with low grade murmurs, for example, may require little or no treatment and the murmur may resolve itself within six months. Routine diagnostic imaging is recommended for dogs with murmurs.”
How Can I Prevent My Dog From Developing a Heart Murmur?
Because there are so many other conditions that can lead to your dog developing heart murmurs, it is difficult to prevent. It’s generally advised that you monitor your dog for any of the symptoms listed above.
According to petplace.com, “If you suspect that your pet has a heart murmur, you should discuss diagnostic options with your veterinarian. Animals with heart murmurs should be monitored periodically to determine if disease is progressive.”
Find A Vet HOW TO articles are intended for informational purposes only. You should always consult with your veterinarian about any health issues affecting your dog.
Do you have a question about heart murmurs? Submit it to i Love Dogs’ Ask a Vet here.
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