Heart Murmur in Dogs: Diagnosis and Treatment

A heart murmur in dogs isn't always a serious problem, but that doesn't mean we shouldn't pay attention to it. In fact, it can be a sign of a more serious heart condition. In that case, an early diagnosis will be essential.

In the following lines, we'll cover how a canine heart murmur develops and what its main symptoms are. We'll also look at how a heart murmur is detected through various diagnostic tests, and what care and treatment a dog with this type of problem needs.

What Is a Heart Murmur and How Do Dogs Get One?

Normally, when listening to a dog's heart with a stethoscope, you should hear two clear sounds ("lub-dub"), which are the normal sounds of the heart valves closing as blood flows through the heart. An additional "whooshing" sound, known as a murmur, is generally associated with a disturbance in blood flow at the heart level.

A heart murmur can be classified into six intensity levels, depending on the volume of the sound (not its severity), so a grade 3 murmur isn't necessarily more serious than a grade 1 one. There are different types of murmurs depending on their severity:

1. "Innocent" murmurs, which usually occur in puppies, are generally temporary and soft.
2. Functional murmurs occur if there's a disturbance in heart flow due, for example, to tachycardia, although they don't necessarily have to be linked to a heart condition.
3. Pathological murmurs occur when one of the valves doesn't open or close fully, when there's an obstruction to blood flow out of the heart toward the major vessels, in cases of structural heart defects... etc.

So, to determine the type and severity of the heart murmur affecting our pet, the vet will need to run different diagnostic tests. Either way, it's very important to reach an early diagnosis to start treatment as soon as possible.

Causes of a Canine Heart Murmur

Often, a pathological heart murmur is linked to a dog's age (just as in humans). As they get older, dogs become more likely to develop this type of problem.

That said, there are various causes that can trigger this turbulence in the blood flow passing through their heart, such as congenital defects in the heart walls, blockages or deficiencies in the heart valves, cardiomyopathies (disorders affecting the heart muscles), endocarditis (infection of the heart valves), or neoplasms (tumors).

It can also be due to a tumor, infections, or diseases such as microfilaria parasitism (heartworm). Small dogs have a greater tendency to develop heart conditions such as degeneration of the heart valves (chronic valvular endocardiosis).

Even so, mini breeds such as the Poodle, Chihuahua, Yorkshire Terrier, or Maltese can end up living for many years with a mitral murmur if they show no symptoms of heart failure. The average age this degenerative condition tends to appear in breeds under 10 kg is around 7-8 years.

Symptoms of Heart Problems in a Dog

Just like the causes, the symptoms of a heart murmur vary case by case, although these are the most common:

• Coughing, dyspnea (difficulty breathing), and/or tachypnea (breathing faster than normal).
• Lethargy, weakness, or listlessness.
• Cyanotic mucous membranes, showing a gray or bluish color, due to a lack of oxygen in the blood.
• Abdominal distension.
• Exercise intolerance.
• Collapse.
• Weight loss.

These symptoms are nonspecific and can also be due to other problems or diseases not directly related to the heart, so it will be necessary to take the dog to the vet so they can examine it and reach a differential diagnosis.

For a reliable diagnosis, bloodwork including a heartworm test may be needed, along with chest X-rays, electrocardiograms, ultrasounds, and blood pressure measurement.

How to Care for a Dog With a Heart Murmur?

The treatment the vet recommends will differ depending on the cause of the heart murmur, its type, and the affected dog's condition. For pathological murmurs, medical treatment could be enough to resolve the problem. However, if it's due to a congenital condition, surgery may be necessary.

To prevent worsening of the signs associated with the heart murmur that could put the dog's life at risk, a series of additional care measures are recommended, such as:

1. Proper nutrition, with special kibble for dogs with heart conditions or a personalized diet that prevents the dog from becoming overweight. This is essential, since obesity can worsen the dog's heart problems.
2. Strictly following treatment. We need to give the medication the vet prescribes rigorously, along with regular check-ups to adjust doses as needed.
3. Moderate exercise. Although it shouldn't be forced, moderate, regular physical activity is good to prevent an overly sedentary life. Short, flat walks will help keep its heart in shape.

Finding out about a heart problem in our canine companion can worry us a lot, but don't panic. Following these recommendations and the treatment a vet gives you, dogs with a heart murmur usually have a fairly good life expectancy.