Something that has always confused me, even before vet school, are heart murmurs. What is a heart murmur? Where do they come from? Why do some of them go away when some are very serious? These questions and more have left me wondering for several years. Finally, in my last semester of the didactic portion of veterinary school, I’ve received some answers about heart murmurs in my cardiopulmonary course.
So, what is a heart murmur? A heart murmur is a sound that can be heard through a stethoscope while auscultating (listening to) the chest. It makes a “whooshing” sound and indicates that there is turbulent blood flow in the heart. Heart murmurs are graded out of 6 on a scale. A 1/6 is pretty hard to hear, while a 6/6 has a “palpable thrill” you can feel when putting your fingertips on the patient’s chest.
Why do some heart murmurs go away? If you’ve ever brought home a new puppy, your vet may have noted a heart murmur at one of the first exams that they were later unable to hear as the dog matured. Innocent murmurs in puppies are a pretty common finding. Remember, a murmur is just the sound of turbulent blood flow. In a puppy, it may be possible to hear a 1-2/6 murmur just due to the fact that the dog is still growing. It’s really important to note that if the murmur is a 3/6 or louder, or if the 1-2/6 murmur doesn’t go away by about 6 months old, further diagnostic tests are needed to rule out a congenital heart disease.
Why do older dogs get heart murmurs? There are several cardiac diseases older dogs can get that result in murmurs. The most common causes are things like valvular disease, heart worm disease, or cardiomyopathies. If your vet hears a new murmur during your pet’s yearly exam, it’s really important to follow up with diagnostic testing to determine why there is a murmur. This might include tests like radiographs, blood work, ECGs, or an echocardiogram, but which specific tests you do will be up to you and your vet.
After years of being confused by heart murmurs, I finally feel like I have an understanding of what they are and what causes them. With this new information, I am ready to go into clinics and start listening to patients to detect any heart murmurs and their underlying causes.