Heart Murmur: Is It as Bad as You Think?

Lub dub, lub dub, lub dub. What is this all about? This is the classic sound, as explained, that you might hear when you would be listening to your dog’s heart with a stethoscope. They are the nice, crisp sounds of a normal healthy heart. However, what if you take your canine friend in for their physical examination and your veterinarian states, “I hear a heart murmur today.” If you are like most owners, your immediate reaction is one of nervousness and anxiety and, either verbally or internally asking, “Now what? Is this bad?”

Initially, you must understand that listening to the heart is only a screening method to detect abnormalities. It doesn’t reveal the reason for or the extent of the abnormality although, based on what is heard, there is some insight as to what may be wrong. A heart murmur is simply the sound of turbulence of blood as it is moving through the heart. It will have a classic whoosh, whoosh sound rather than the lub, dub. Imagine holding a garden hose with the metal end removed and water rushing out. Now grasp the end and gradually squeeze the end down with your fingers. You will feel the vibrations as the water is jetting out. This is what turbulence of the blood may be like.

One of the most common causes of heart murmurs, especially in more mature and smaller breeds of dogs, is created due to the mitral valve within the heart being distorted, leading to what is termed an insufficiency. The valve is not functioning properly, leading to blood leaking back into (in the case of mitral valve disease) the left atrium. This can eventually lead to enlargement of both the left atrium and ventricle of the heart.

There are four stages/categories of heart disease: Stage A, Stage B (further broken down to B1, and B2), Stage C, and Stage D.

  • Stage A is simply breeds of dogs that may be at higher risk of heart disease with no current signs or symptoms.
  • Stage B is where the murmur is heard but no outward signs are noted.
  • With Stage C, your dog is experiencing outward signs of heart trouble and treatment is necessary.
  • Stage D is when there is heart failure and where managing the disease is becoming difficult.

So, since we have heard a murmur we are at least in stage B. Your veterinarian will likely recommend some further testing to determine more precisely to what degree of heart disease is currently present. Tests that will likely be recommended include: x-rays of the chest (heart and lungs), some blood work to check on liver and kidney function, possibly blood pressure measurement, and an ECG (electrocardiogram). An ultrasound/echocardiogram may also be recommended.

After testing is performed, there may or may not be any further treatment. For example, if the heart size is normal and all else is good, any further treatment may not be recommended. This is stage B1. If the heart is showing enlargement but lungs look good, this would be a stage B2. While there is no immediate need for treatment in either of these stages you, as the owner, now take an active role in monitoring your dog’s wellness.

One method of monitoring at home is by measuring and logging, consistently, your dog’s resting respiratory rate (RRR). Your vet can explain in more detail on how this is done. It is very easy, and there is even a phone app that can be downloaded to help you keep track and log these values. Depending upon the stage, you may need to do this monthly to weekly, noting that an increase by about 30% in the RRR is significant and indicates follow-up examination by your vet.

Other symptoms to be aware of include:  coughing, changes in breathing patterns, difficulty breathing or shortness of breath, changes in behavior such as lack of energy and tiring more easily than normal, restlessness (especially at night,) and changes in appetite. If you notice any of these symptoms this may be an early warning sign that the heart disease is worsening and your dog needs to be examined.

The take home message is: just because a heart murmur is heard doesn’t mean a doom and gloom picture. Many dogs with murmurs can live a normal life expectancy and be active and otherwise healthy. However, these dogs should be continually monitored both at home and by your vet. Even with more significant heart disease (stage C), oftentimes with medication, your dog’s heart condition and the associated symptoms can be dramatically improved. These treated dog can be very happy with no apparent outward symptoms.

And as always – if you have any questions or concerns, please ask me in the comments below. 


-Photo Credit: Dr. Rod Van Horn listening to a dog’s heart at the Omaha Animal Medical Group, where he is a practicing veterinarian.

Tags: , , ,

  • Print
  • email