Heart murmur in dogs

Just like humans, dogs can suffer from cardiovascular diseases, frequently revealed by a particular phenomenon: the heart murmur.

Although the detection of a heart murmur in his four-legged friend can quickly panic the owner, this phenomenon is not always synonymous with serious problems. However, more thorough health examinations are generally essential to judge the severity of the underlying condition and to set up an appropriate treatment, especially when the dog's life is threatened.


What is a heart murmur in dogs?

A heart murmur is an abnormal sound detected when the dog is auscultated with a stethoscope. A heart murmur is actually a symptom, not a disease. It can be related to a wide range of conditions that require further investigation to identify.

As in humans, dogs can have a mild heart murmur that does not impair their quality of life or impact their longevity. However, in some individuals the heart murmur reveals heart disease, so the prognosis is sometimes uncertain. Note that the intensity of the noise is not a factor of severity.

The dog's heart is a muscle whose role is to pump blood to allow it to circulate in the body, in particular to transport oxygen from the lungs to the various tissues and organs. It is a vital organ, whose malfunction threatens the integrity of all other organs in the body.

The heart is composed of four chambers, two ventricles (right and left) and two atria (right and left). In principle, the right ventricle and atrium of the heart should not communicate with the left ventricle and atrium. Each chamber has valves that prevent backflow, so that the blood flows correctly, always pushed in the same direction, in time with the heartbeat.

A heart murmur can be heard when the integrity of this complex system of chambers, vessels and valves is compromised. The abnormal noise that can be heard is caused by a leak, as blood escapes from the normally closed circulatory system and takes a circuitous route.

The blood then risks not only not arriving where it should, but also causing deformations of the tissues that it pushes, under the pressure of the heart, instead of remaining in the vessels. The heart then no longer fulfills its role properly, and this is heart failure. Not all heart diseases cause a heart murmur, and not all "leaks" are heard when the dog is examined.


Symptoms of a heart murmur in dogs

A heart murmur is only an abnormal sound that can be heard when the animal is examined with a stethoscope. It does not cause any symptoms: it is a symptom. The possible cardiac pathology at the origin of this noise can generate additional symptoms that accompany the heart murmur, especially in the case of cardiac insufficiency.

However, these are neither specific nor systematic. A large number of phenomena can indeed result in a heart murmur, and some do not cause any other symptoms. In the case of cardiac pathology, a progressive evolution in three phases can generally be observed.

The first phase is asymptomatic and is the reason why heart disease is known as the "silent killer". During this phase, the disorder progressively sets in and worsens, but the animal shows no symptoms. The heart murmur is usually discovered incidentally during a check-up or during a visit for some other reason.

The second phase is when the first symptoms appear, and the heart is no longer able to compensate for its loss. The dog may become short of breath, breathing faster and harder. Aware of the problem, the dog may tend to self-limit, and the owner will only notice a decrease in activity without any other clinical sign.

A dry, discrete, chronic and/or hacking cough is a typical symptom of cardiac disease in dogs. The third phase marks the beginning of the real problems, as the dog's heart can no longer perform its duties properly, thus impacting the functioning of the animal's other organs.

Shortness of breath is marked, coughing is frequent, complete intolerance to exertion is observed, and the animal is tired, depressed and sad. A deterioration of the dog's general health may occur, with weight loss, loss of appetite, then syncope and/or respiratory distress. Ascites, the presence of fluid in the abdomen, is sometimes present.





Causes of heart murmur in dogs

The causes of a heart murmur in dogs can be congenital, traumatic, bacterial, viral, or metabolic. Broadly speaking, a distinction is made between congenital heart disease, which affects the dog from birth, and acquired heart disease, which occurs later in life.

Congenital heart murmur in dogs
Heart murmurs in dogs can be caused by various congenital heart defects. This type of condition is still relatively rare, accounting for about 5% of all heart disease in dogs. Moreover, congenital heart disease is usually diagnosed early and, when possible, operated on in the first days of the puppy's life.

Patent ductus arteriosus is one of the most common congenital heart defects. If left untreated, it leads to death in 60% of cases before the age of 18 months. This disorder causes no visible symptoms, and is often detected by chance during an auscultation, when the veterinarian detects a heart murmur.

Malformations of the chambers or valves of the heart also exist in the dog, as well as congenital shunts, anomalies creating a passage between two chambers that does not belong and disturbs the circulation.

Acquired heart disease
Acquired heart disease develops over time as the heart deteriorates with age, whether or not due to a genetic background that favors the occurrence of cardiac deformities. The most common disorder in this category is Mitral Degenerative Valve Disease, which is a deterioration of the valve in the left atrium that loses its tightness.

It accounts for 75% to 80% of acquired heart disease and preferentially affects small dogs. Large dogs are not left out with Dilated Cardiomyopathy, a pathology involving a dilatation of the chambers of the heart, which then lose their pressure power and pump blood less efficiently.

In addition to congenital or acquired heart defects, it should be noted that trauma, poisoning, parasites and infections can also cause a heart murmur.


Treatment and prognosis of heart murmurs in dogs

The treatment of a heart murmur depends intimately on its cause, and this cause must imperatively be sought to offer the animal a chance to live its life in good conditions and to reach a normal longevity. Some congenital heart diseases can be surgically operated, and the animal is then free of its problem for life, provided that it has been treated before the first symptoms of heart failure appear.

In older dogs or pooches with a non-operable condition, a certain lifestyle should be implemented to preserve the heart muscle and avoid complications. Medical treatments can also support the heart over the long term. When the murmur is caused by the presence of parasites or pathogens, treatment is aimed at eliminating the culprits and then supporting the heart's function in case of sequelae.





How to recognize a heart murmur in dogs?
A heart murmur is an abnormal noise in the dog's heart. It cannot be observed or felt, but only heard by a veterinarian with a stethoscope.

How do I know if my dog has a heart murmur?
A heart murmur in dogs can only be detected by listening to the animal's heart with a stethoscope. The best way to be sure that everything is fine is to have regular check-ups with your veterinarian. However, signs of heart failure can also indicate the presence of a heart murmur: shortness of breath, fatigue, decreased activity, intolerance to exertion, dry cough, swelling of the abdomen are all symptoms that should alert you.

What causes heart murmurs in dogs?
There are many things that can cause heart murmurs. Most often, a deterioration of the valves and chambers is the cause. The latter occurs with age, due to the aging of the heart muscle. Congenital malformations can also be involved, as well as trauma, infections or parasites.

Can a heart murmur be treated in dogs?
Heart murmurs are not a disease, but a symptom, and only the cause can be treated - when possible. In some cases, heart murmurs do not require treatment and do not affect the dog's life. In the case of congenital malformations, early surgery may be indicated.

Ultimately, a heart murmur does not always indicate a serious disorder, and not all serious cardiac disorders produce a heart murmur. It is therefore essential not to systematically associate "heart murmur" and "heart failure", two phenomena that are easily confused.

A heart murmur is only an abnormal noise and, in the absence of further veterinary investigations, it would be unwise to automatically attribute it to a cardiac pathology, especially in a dog in the prime of life and in good health, especially since cardiac disorders are rather rare in dogs.

However, it is a good idea to offer your dog regular check-ups and, if a heart murmur is detected, not to neglect to carry out additional examinations to determine the cause: in the event of a problem, early treatment always offers a better prognosis.