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Summery :

1. What is a heart murmur in dogs?
2. What are the causes?
3. How serious is it?
4. What are the symptoms?
5. What tests should be done for diagnosis?
6. How to cure it?
7. What is the prognosis?
8. Heart murmur in puppies, what are the causes?

1- What is a heart murmur in dogs?

Also known as a heart murmur , a heart murmur is an abnormal noise, similar to a whooshing or hissing sound, detectable through a stethoscope, which is added to the classic heart sounds, those that indicate the heartbeat (the so-called “lub” and “dub” sounds).

Heart murmur in dogs is a disorder that should not be underestimated and whose symptoms should be monitored, with the awareness that it is necessary to contact the vet immediately if the animal is ill.

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2- What are the causes?

A heart murmur is a result of turbulent blood flow within the heart chambers (atria and ventricles) and through the heart valves .
It can be caused by various conditions, including:

• Heart disease, acquired or congenital;
• Anemia (low levels of red blood cells );
• Pregnancy;
• Hyperthyroidism ;
• Fever ;
• Cardiopulmonary filariasis ;
• Hypoproteinemia (low levels of protein in the blood);
• Obesity.

It should be noted that there are also so-called innocent murmurs , of a benign nature , which occur as a result of very rapid blood flow within the heart chambers; generally, innocent murmurs affect puppies, especially large, rapidly growing ones, and resolve spontaneously after 4-6 months of life.

Heart Diseases

The most well-known heart disease associated with heart murmurs in dogs is mitral insufficiency (or mitral regurgitation ); it is a valvular disease (i.e. a disease of a heart valve), which involves a structural alteration of the mitral valve (located between the left atrium and the left ventricle ) and the consequent dysfunction of the same (the valve “leaks” blood and returns towards the left atrium instead of continuing into the aorta ).

Other heart conditions that can cause a heart murmur in dogs include:

• Dilated cardiomyopathy ;
• Bacterial endocarditis affecting the heart valves;
• Congenital defects of the interventricular septum or atrial septum;
• Tetralogy of Fallot in dogs;
• Subaortic stenosis , pulmonary stenosis and patent ductus arteriosus, whose common denominator is that they are hereditary congenital anomalies.

Anemia and hypoproteinemia

The scarcity of red blood cells in the blood (anemia) and, similarly, low blood levels of proteins (hypoproteinemia) make the blood more watery and fluid, which is why turbulent flows are more likely to form inside the heart chambers.

Potential causes of anemia and hypoproteinemia are:

• Severe blood loss;
• Intestinal worms ;
• Fleas ;
• Ticks .

Pregnancy

Sometimes, heart murmurs in dogs can appear as a result of pregnancy ; fortunately, most of the time, the problem is benign and resolves spontaneously as soon as the dog has given birth.

Cardiopulmonary filariasis

Cardiopulmonary filariasis , or more simply filaria, is a serious parasitic disease caused by the action of a worm, Dirofilaria immitis , which settles between the heart and lungs , seriously compromising the health of these organs.
Filaria is a potentially fatal disease, with a very slow progression.

3- How serious is it?

The severity of a heart murmur in dogs varies: some murmurs are physiological (so-called innocent murmurs); others reflect a mild health problem, which however should still be monitored; still others are the consequence of a serious condition.
Characteristics of the murmur that help describe its severity are:

• Noise intensity;
• When it occurs;
• Duration;
• Which part of the heart does it come from.

It is the veterinarian’s job to correctly interpret the severity of the murmur and adopt the right treatment.

Depending on how serious the problem is, the therapeutic approach also changes.
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4-What are the symptoms?

Heart murmur in dogs can manifest itself with:

• Loss of appetite and weight loss .
• Cough ;
• Lethargy ;
• Weakness and easy tiredness;
• Difficulty breathing (the dog pants excessively even after simple efforts), rapid breathing and/or dyspnea
• Collapse
• Swollen abdomen
• Pale gums;

5- What tests should be done for diagnosis?

The detection of a heart murmur in dogs is typically done through cardiac auscultation with a stethoscope.

To detect a heart murmur in a dog, cardiac auscultation performed with a stethoscope (or phonendoscope) is sufficient. During this examination, the veterinarian also evaluates the degree of loudness of the abnormal noise, a characteristic that is not always related to the severity of the problem.

Once the murmur has been identified, it remains to be understood whether the anomaly is due to a specific heart disease (structural defect, endocarditis, valvular disease, etc.) or to an extracardiac condition (e.g. anemia, pregnancy, hypoproteinemia).
To clarify this aspect, the veterinarian uses various tests: first, he evaluates the animal’s clinical history in relation to age and present symptoms ; subsequently, if further investigation is needed, he also relies on:

• Chest X-ray ;
• Electrocardiogram (ECG);
• Echocardiography ;
• Blood tests .

Such an approach is important to avoid unnecessary checks; the basic idea is to first understand the real extent of the problem and then, if necessary, investigate further.

Grades of Heart Murmur in Dogs: How Many Are There and What Do They Mean?

Although not always directly proportional to the severity of the murmur, the intensity of the abnormal noise is an important parameter used to classify heart murmurs in dogs.
The classification based on the intensity of the noise distinguishes 6 degrees of heart murmur, identified by the first six Roman numerals:

• Grade I murmurs : These are the least audible, barely perceptible murmurs. They are generally not serious.
• Grade II murmurs : These are slightly louder than the previous ones, but still quite quiet.
• Grade III murmurs : These are murmurs that are easily detected with a stethoscope, as the intensity of the noise is significant. They can indicate an important health condition, at least to be monitored over time.
• Grade IV murmurs : These are murmurs whose intensity is between grade III and grade V murmurs. They are easily audible with a stethoscope and should at least be monitored over time, because they could be the result of a serious condition.
• Grade V Murmurs : This category includes murmurs that can be detected simply by placing a hand on the dog’s chest.
• Grade VI murmurs : These are even louder murmurs than the previous ones. In fact, they can be heard when the stethoscope is not even placed on the animal’s chest .
  They generally indicate a serious health condition.

Heart Murmur in Dogs: What Other Features Should You Consider?

The intensity of the noise provides important indications, but, as previously mentioned, to correctly interpret the severity of a murmur the veterinarian must also evaluate other parameters, which are:

Which part of the heart is it coming from ? The location where the murmur is heard best helps determine which valve is malfunctioning and which chambers of the heart are affected.d peaceful atmosphere, where other guests seem comfortable, you may have found the right place.

When the murmur occurs . A murmur can occur in the systolic phase (when the heart contracts ), in the diastolic phase (when the muscle relaxes), or constantly throughout the entire heartbeat cycle .

Duration of the murmur . A heart murmur can be long or short.

6- How to cure it?

Treatment varies depending on the severity and cause of the heart murmur .

Generally, if the dog has a mild heart murmur of little clinical relevance (also called a physiological murmur), the therapeutic management is limited to periodic monitoring of the animal’s cardiac conditions , in order to evaluate the progress of the problem and identify any worsening in good time.

On the contrary, if the murmur in the dog is attributable to a specific pathology (anemia, hyperthyroidism, mitral insufficiency, etc.), a specific therapeutic plan is needed , which, depending on the case, could include

• Drugs (inodilators or phosphodiesterase inhibitors, diuretics , ACE inhibitors , etc.);
• Specific diet ,
• Cardiac surgery and
• Other supportive care .

Clearly, even in these more complex cases, periodic monitoring of the animal’s health conditions remains essential.

7- What is the prognosis?

For a dog, the prognosis for a heart murmur is variable: it all depends on the nature of the problem and the effects of the therapy.

Generally speaking, the more serious the cause of the murmur, the more uncertain the prognosis. That said, however, it should be noted that even in the presence of serious heart murmurs, current therapies can be extremely effective and drastically improve the animal’s health conditions.

8- Heart murmur in puppies, what are the causes?

Puppies can also have a heart murmur.
In these cases, there are two potential causes:

• The aforementioned innocent murmur , due to growth and destined to disappear after a few months of life.
• Congenital heart defects . Murmurs that result from them are usually loud and, depending on the case, may require periodic monitoring of the animal’s health conditions or corrective heart surgery.