I think the other way around is possible, but I don't believe AFib can cause a murmur. If murmur is due to a leaky valve, that can cause enlargement of the atrial chamber, and that can cause AFib. That is more or less what happen to me. My condition was never called a murmur, it was called a leaky valve. This may be because the leaky valve in my case didn't make enough noise to hear on a stethoscope - it was found with an echo cardiogram.