What is the life expectancy of my old dog with a heart murmur?


With age comes an inevitable decline in health and vitality. Our pets are unfortunately subject to such deterioration the same way us humans are. Finding out that your dog is having heart problems can be very frightening. You’re suddenly forced to confront the reality that your dog isn’t going to be around forever. A heart murmur can be a result of a dire heart condition, but it can also just be a mild symptom of a cardiac cycle operating in a less than optimal manner. There are different levels that categorise the severity of the heart murmur, and fortunately not all of them are extremely serious. Hopefully the following information will help you to better understand your dog’s condition.

What is a heart murmur?

As you well know, the heart is a muscle designed to carry blood throughout the body to supply the skeletal muscles and organs with the necessary oxygen and nutrients they need. It does so by contracting and thereby pumping the blood to where it needs to go. A low resting bpm (heart beats per minute) is considered healthy as it is an indication that the heart is strong and can adequately push blood through the network of arteries and veins without excessive resistance. A high resting bpm suggests that the heart is weak or there are other underlying conditions reducing an effective cardiac cycle. When an abnormality is present in the flow of blood, it makes a sound which is referred to as a murmur. This is distinctly different from the normal rhythm of the heart that you’ll hear through a stethoscope.

What are the possible causes of heart murmurs?

One of the most typical causes of a heart murmur is myxomatous mitral valve degeneration (MMVD), also known as endocardiosis. Between the left ventricle and left atrium is where the mitral valve sits. This valve is partly responsible for maintaining the appropriate flow of blood. The regular beat of the heart that everyone knows is ideally all that should be audible when listening to the heartbeat. The degeneration of the mitral valve is when the typically thin leaflets of the valve become unusually thick and often bumps will form at the edges. This can keep the leaflets from shutting properly like they’re supposed to. Essentially the valve starts to leak as it fails to completely close and the blood flow becomes unstable, which creates the foreign sound (murmur). With myxomatous mitral valve degeneration, the murmur can be heard between the two beats of a normal cardiac contraction (between the “lub” and the “dub”). It is often detected the most discernably at a specific spot on the left region of the chest.

In fact MMVD is so commonly responsible for heart murmurs that many veterinarians will automatically anticipate that it’s the likely cause for your dog’s heart murmur. If there are no other obvious causes, MMVD will undoubtedly be the number one suspect. This can be confirmed with an echocardiogram and X-ray. The initial symptom you want look out for is coughing. As the left atrium swells due to the excess inflow of blood from the compromised valve, the over-sized atrium adds pressure to your dog’s airway, causing aggravated breathing. There are other factors that may also be responsible for your dog’s cardiac condition. For example, the abnormality could be created by obstructed or diseased valves.

Diastolic murmurs occur less frequently in canines. The primary factor for this type of murmur is a malfunctioning aorta. The valve of the aorta can’t form a proper seal which of course affects the blood flow. Other possible causes include pulmonic valve endocarditis and mitral valve stenosis. On the other hand, systolic murmurs are much more common. Pulmonic and subaortic stenosis are often the main contributors in this scenario. This is when the blood vessel become uncharacteristically narrow, creating an impeded flow of blood. There are a number of other potential reasons for systolic murmurs. Cardiomyopathy, heartworm disease, systolic anterior mitral motion, mitral valve failure, anemia, hyperthyroidism, or a faulty aortic valve are all possible causes of a systolic murmur

Different kinds and grades of heart murmurs

We’ve already covered systolic and diastolic murmurs, but there is a third type known as a continuous murmur. A murmur is categorised by the timing of the abnormality. A murmur is referred to as systolic if it is heard upon contraction of the cardiac muscle. A diastolic murmur is detected in between contractions (when the heart is at rest). A continuous murmur takes place at either or both of these stages of a cardiac cycle.

The grading of heart murmurs is categorised as follows: 

  • Grade 1 – This is the least threatening condition as the irregular sound can hardly be heard using a stethoscope.
  • Grade 2 – The murmur is light but the vet will surely notice it using his or her stethoscope.
  • Grade 3 – At this stage, extra concern is warranted as the murmur is distinct and it’s from this level upwards where serious issues could arise.
  • Grade 4 – A heart murmur is very audible and can be detected on both sides of the dog’s chest.
  • Grade 5 – Using a stethoscope, picking up on the murmur is very easy as it is extremely noticeable. It’s so distinct that it can even be detected by simply pressing a hand up against the dog’s chest.
  • Grade 6 – This is essentially a stronger version of a grade 5 murmur. The sound is particularly audible and the irregular heartbeat can easily be felt by holding your hand on the dog’s chest.

There are also four discernable rhythms or configurations of murmurs which can give the vet a better idea of where the cardiac inconsistency might exist.

  • Crescendo-decrescendo murmurs – These murmurs increase and decrease in volume and are thought to be linked to pulmonic stenosis and aortic stenosis.
  • Decrescendo murmurs – This is when the murmur begins very audibly and then gradually becomes less noticeable. This configuration is usually associated with defective aortic valves or possibly septal defects of the ventricles.
  • Plateau murmurs – Murmurs such as these are typically steady and distinct. This if often related to aortic valve insufficiency.
  • Machinery quality murmurs (also known as continuous murmurs) – This configuration usually correlates with a congenital cardiac condition known as patent ductus arteriosus (PDA).

Every kind of murmur comes with an abundance of information and can be scary to learn about initially. Your vet should be able help identify the type of murmur your dog may be dealing with so you can have a better understanding of the situation. However, medical professionals are just people and people often make mistakes. If you can afford it, getting a second opinion from a different veterinarian could also help to provide you with some clarity.

Is there treatment available?

Depending on the severity of your dog’s condition, different treatment options may or may not apply. If your dog is suffering from myxomatous mitral valve degeneration but not congestive heart failure (CHF), the vet is likely to recommend that your dog is kept under close watch to ensure their situation doesn’t deteriorate. Your vet might also suggest some cough medicine to ease you pooch’s aggravated respiratory system. There currently isn’t a lot of evidence to suggest that other types of therapy are necessary prior to congestive heart failure.

Regular visits with the vet are recommended as you’ll obviously want to know as soon as possible if CHF develops. There are a few options that can treat CHF such as furosemide (a medicine used to inhibit the build-up of fluid in the dog’s lungs), enalapril (a drug used to combat heart failure, high blood pressure, and kidney failure), and pimobendan (a calcium sensitizer often used to treat heart failure in dogs). A few cardiac anomalies, like pulmonic stenosis or PDA, can sometimes be fixed with surgery.

Based on the grading of the murmur you can estimate how serious your dog’s condition may be. A grade 5 or 6 murmur is a significant indication of compromised cardiac functionality, meaning your dog is in a very fragile position and your full attention will be required if you hope to correct the problem. A lot of dogs have gone on to live long and happy lives after their heart murmur was discovered. It’s also not unheard of for dogs with heart failure to live for several years after their diagnosis. However, if their situation doesn’t look good, all you can do is provide them with the best quality of life you can offer and try to make them as comfortable as possible in their final years. Try to give them a nutrient -rich diet with moderated levels of protein and sodium and make sure they don’t suffer from dehydration.


Getting old isn’t pleasant for anyone, but a higher quality of life is always more important than the number of years you survive. Depending on the intensity of your dog’s heart issues, you can remain confident about your canine’s life expectancy. Ask your veterinarian about how your dog’s heart murmur is graded and what treatment options you might have available to you. Also consult your vet about an appropriate diet that will work best for a frail heart condition. Last but not least, try to do everything you can to reduce the stress in your dog’s life. Stress is known to be a major influential factor linked to heart failure and should be avoided or reduced by all means possible.