Does a Heart Murmur’s Intensity Mean Anything?


Yesterday Karen posted a comment on my July post about heart murmurs in cats.

My vet tech just informed me that my 15 year old cats heart murmer increased to a 2.5 on a scale of 1-4. Im not sure what significance this has to her condition. Any information to give?

Heart murmur intensities are graded on a scale of 1 – 6 (not 4, at least where I practice). The intensity of the murmur is a measure of how loud and prominent the murmur is when a clinician listens to it. People often make a big deal out of murmur intensities. Generally, however, one should not focus too much concern on a murmur’s intensity, because there is not a very good correlation between the intensity of a murmur and the degree (or presence or absence) of heart pathology.

When a heart works normally, blood flows through it in a non-turbulent (or, as technical people say, laminar) fashion. A murmur signifies turbulence in the heart. However, a very small amount of turbulence sometimes can cause a great deal of noise. Conversely, a walloping amount of turbulence sometimes causes very little noise at all. The noise to which I’m referring is what clinicians are listening to when they talk about heart murmurs.

Therefore the best way to monitor your pet’s heart status is not through repeated auscultations (episodes of listening) to the heart. The murmur’s intensity may fluctuate or change, but this won’t tell you what’s going on with the heart. Your cat needs diagnostic imaging. X-rays and ultrasound are the only ways to determine whether the murmur, regardless of intensity, is anything to be worried about.

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