When you judge the severity of mitral regurgitation, would you believe you don’t primarily listen in systole? Even while the murmur may be quite loud, and intense, and impressive, it’s diastole, you listen in diastole. Why? Because diastole reflects flow back across the valve and that reflects how severe the mitral regurgitation was. Specifically, if you get just a little bit of mitral regurgitation, well, there isn’t an awful lot of blood coming back across the valve in diastole, but if you get moderate mitral regurgitation, that could generate an s3. So that mild mitral regurgitation might be [mimics sounds], moderate would be [mimics sounds]. The third sound because there is that accelerated blood going into the ventricle, it decelerates generating that low-frequency sound. And finally, if it’s severe mitral regurgitation, you may get an almost relative mitral stenosis, because there is so much blood coming back across the valve in diastole, it actually generates a flow rumble. So, severe would be [mimics sounds]. Again, mild [mimics sounds], moderate [mimics sounds], severe [mimics sounds]. Quite a pearl, listen in diastole for the acoustic events that reflects the severity of mitral regurgitation that occurs in systole.

MR severity by the acoustic events

In mitral regurgitation, the severity of the lesion is not accurately reflected by the systolic murmur’s intensity. The diastolic acoustic events do relate to severity. In patients with severe mitral regurgitation, the left atrium is overfilled during the previous systole, and a larger than normal volume of blood enters the left ventricle during diastole. This results in an audible third heart sound with or without a flow rumble.