My murmur was a grade 5-6/6. I think that particular number has to do with how loud it is because my OB graded my murmur when I was pregnant after listening through the stethoscope. Although the volume relates to the severity, a louder murmur can be less harmful than a softer murmur. Every doctor that listened to mine was amazed that it was so loud and I was still walking around.
However, the jet that caused the noise was 3+, which as Gary said, is between moderate and severe. This number is also misleading because some people develop this type of problem over time, giving their hearts time to adjust, and some people develop it quickly, which is a more serious problem.
After my Cath, I was told that if someone suddenly developed the problem I had, they would be dead. However, since it had taken me 22 years to get to that point, my heart had compensated by enlarging and pushing more blood than normal required through the damaged valve (85% EF).
That is why doctors looks at all the numbers plus symptoms before recommending surgery.
