Heart Murmurs In Dogs: Everything You Need To Know

It can be scary when your vet informs you that your dog has a heart murmur. But the most worrying thing is that if you’re unaware of heart murmurs and their implications, it can be challenging to understand the situation and what needs to be done.

Heart murmurs are abnormal heart sounds. Generally, they arise due to the presence of turbulent blood flow in the heart and are caused by valve defects such as mitral or tricuspid insufficiency or aortic stenosis. There are three types, six grades of murmurs, and four configurations for each type. 

In most cases, these issues can be managed with medication and lifestyle modifications. However, surgery may be necessary for specific instances.

What Are Heart Murmurs in Dogs?

Heart murmurs are whooshing or swishing sounds coming from your dog's heart. They’re caused by turbulent blood flow through the valves and can be detected with a stethoscope. A normal heartbeat has two sounds like "lub-DUP" when the valves close.

Upon attentive listening, your vet may detect a peculiar sound coming from your dog's cardiovascular system: a heart murmur. This noise may be barely audible or so loud that the vet can even feel a whooshing sensation on his hand while placing it on the dog's chest.

A dog's typical respiration rate is 15 to 30 breaths per minute. However, if your pup is breathing more than 35 times a minute while resting or sleeping, this could indicate cardiac issues, and you should immediately contact your vet.

Different Kinds Of Heart Murmurs In Dogs

There are two phases in a heartbeat: systole (the contraction of the heart muscle) and diastole (the relaxation of the heart muscle). Thus, heart murmurs can be categorized into three distinct types: systolic, diastolic, and continuous – based primarily on when the murmur is heard in relation to the heart's cycle.

Systolic Murmurs

Heart sounds that are heard during the systolic phase of the cardiac cycle usually indicate an underlying problem with the valvular apparatus or other cardiac structures. During peak heart contraction, systolic murmurs can indicate a severe medical condition.

Diastolic Murmurs

Sounds are heard during the diastolic phase of the cardiac cycle and can indicate an underlying problem with the heart's relaxation. These murmurs are regular signs of an issue with the left atrium or mitral valve apparatus.

Continuous Murmurs

Continuous murmurs are heard during both phases of the cardiac cycle. This is often indicative of a structural abnormality of the heart, such as patent ductus arteriosus or pulmonary valve stenosis.

What Are The Grades Of Heart Murmurs In Dogs?

With the help of a grading system, veterinarians can pinpoint the cause of heart murmurs, ranking them on a scale from one to six.

• Grade I murmurs are easily detectable through a stethoscope, yet they present minimal risk to the patient's health.
• Grade II murmurs are faint. A qualified veterinarian with his expertise can easily detect them.
• Grade III murmurs I are typically louder than Grade II and quieter than Grade IV. However, this type of murmur is usually the most concerning since they often cause serious issues.
• The sound of Grade IV murmurs is unmistakable and can be heard from both sides of the dog.
• The thrum of Grade V heart murmurs is so strong that a vet can pick up the sound without difficulty while placing his hand on the dog's chest, giving him an almost tangible sensation as it rumbles.
• Grade VI murmurs are the most severe heart murmurs, and their loudness can be heard through even thick walls as if they were a thunderous sound. These are extremely intense and far surpass other minor grades of murmur intensity.

There are four configurations (referred to as qualities) of heart murmurs as well:

• Plateau murmurs
• Crescendo-decrescendo murmurs
• Decrescendo murmurs
• Machinery murmurs

Life Expectancy In Different Heart Murmur Grades In Dogs

The longevity of dogs with heart murmurs can vary vastly depending on the medical condition causing them, as there are numerous reasons a dog may have one.

Grade I and Grade II murmurs are considered very mild, with most dogs having a prognosis of an average life expectancy.

Grade III and Grade IV murmurs can affect the dog's life expectancy, depending on their underlying condition and the treatment they receive.

Grade V and Grade VI murmurs are serious cardiac conditions with potentially life-threatening implications. Many dogs have a median lifespan of 1-2 years when these heart conditions are present. 

Even more concerning is that if the dog experiences concurrent arrhythmias in addition to their murmur, this drastically decreases his survival time to only six months or less.

Root Causes Of Dog Heart Murmurs

An array of health issues may cause a dog's heart murmur, ranging from benign to more serious. The following are some of the most frequent causes of canine heart murmurs.

Causes Of Systolic Heart Murmurs

A variety of conditions can lead to the development of systolic murmurs.

• Hyperthyroidism - excess production of thyroxine hormones by the thyroid glands.
• Anemia - reduction in hemoglobin levels within the blood.
• Heartworm disease - a fatal condition caused by parasitic worms.

Causes Of Diastolic Heart Murmurs

Diastolic murmurs can commonly be attributed to the following causes.

• Aortic insufficiency
• Mitral and tricuspid valve stenosis - obstructs blood flow
• Endocarditis on either the aortic or pulmonary valves - an extremely dangerous inflammation

Causes Of Continuous Heart Murmurs

Two of the most common sources of persistent murmurs in canines are patent ductus arteriosus and aortic regurgitation. Patent ductus arteriosus is an enduring opening between the two primary blood vessels adjacent to your dog's heart. At the same time, aortic regurgitation transpires due to a faulty valve closure that results in the backflow of blood from its left ventricle.

Signs And Symptoms Of Heart Murmur in Dogs

Depending on the type of heart condition your dog has, he may display various symptoms that indicate something is wrong. Common signs and symptoms include:

• Irregular heartbeat or rapid pulse
• Persistent coughing
• Excessive panting, even when at rest
• Lack of appetite and energy levels plummeting
• Collapsing or fainting spells
• Bluish gums and tongue coloration
• Severe water retention

Which Dog Breeds Are Prone To Heart Murmurs?

Although any dog can develop a heart murmur, some breeds are more prone to this condition than others. This is likely due to specific breeds having a genetic predisposition toward developing various cardiovascular problems than others.

Certain dog breeds should be monitored more closely for heart murmurs, including: 

• Yorkshire Terriers 
• Cavalier King Charles Spaniels
• Doberman Pinschers 
• Poodles 
• Cocker Spaniels 
• German Shepherds

How Are Heart Murmurs Diagnosed?

With a simple stethoscope, your vet can detect your dog's grade and type of heart murmur. After accurately determining what kind of murmur is occurring, he will seek to uncover its source.

Additional Tests

To understand the origin of a murmur, various tests are available such as:

• Chest X-rays
• Echocardiograms
• Electrocardiograms
• Blood test
• Urine tests

This way, a suitable course of treatment can be prescribed once the cause is determined.

Diagnosis By Echocardiogram

The echocardiogram and Doppler examination are the most effective methods of detecting a heart murmur. This combination allows you to acquire real-time images of the beating heart while also calculating blood speed and direction passing through its valves, chambers, and surrounding structures.

The precision of this assessment is unparalleled in locating which areas generate murmurs or other irregularities - giving you peace of mind that your prognosis is determined with accuracy!

How Are Heart Murmurs Treated?

Diagnosing the cause of a dog's heart murmur is essential in determining an effective treatment plan. In cases where no underlying problems exist, regular monitoring may be all that is necessary to ensure his wellbeing. 

If there is an underlying problem causing your dog's blood to flow turbulently, personalized diets and medications can help your dog get better. Your dog will also receive supportive care from medical professionals while he is recovering.

If your dog suffers from certain congenital heart defects, including pulmonic stenosis and patent ductus arteriosus, corrective surgery is an option. Veterinarians will assist you in determining the best course of action to ensure that your dog receives the highest quality care available.

What Sort Of Prognosis To Expect In Heart Murmurs

In many cases, heart murmurs can signify treatable conditions and may even resolve on their own without medical intervention. Prompt recognition of the murmur is essential to address the underlying problem quickly. This is especially important for older dogs with a more guarded prognosis. 

The prognosis can vary depending on the source of the murmur, ranging from excellent to severe. Physiological issues often require no treatment and have favorable to outstanding outcomes, while functional problems may be resolved with medication over time. 

The prognosis for dogs diagnosed with a congenital heart problem is variable. If remediable surgically, an excellent outcome should be expected.

The veterinarian will explain the best course of action and treatment tailored to your dog's individual needs. Regular diagnostic testing must also be performed to ensure success. 

Final Thoughts

Heart murmurs in dogs are not a reason to panic, but they should never be neglected either. An early diagnosis will help you choose the best solution for your dog's health and well-being. 

If you think your dog may have a heart murmur, make sure to reach out to your vet immediately and follow all his recommendations. With diligent monitoring, supervision, and expert guidance, it’s possible to guarantee top-notch care for your furry friend!