Thread: Stage 3 heart murmur

I'm a new guy so bear with me. I searched to see if I could find other posts on this, but while close, not quite there. My wife and I have purchased two MCs from a reputable breeder here in Virginia. They are both 5 months old now, male, and came with medical documents describing their parents. No problems. One of our kittens has checked out perfectly by the vet, however, our second kitten appears to have a stage 3 murmur. The breeder has offered to give us another kitten, and said we could keep the one with the murmur. She is also going to take the kitten to her cardiologist. Apparently, stage 3, if that is substantiated by the cardiologist, is bad from what I understand, with little hope for the future. The kitten tested out fine while with the breeder so this is something he must have grown into after his checkups. Does anyone have experience with this level of murmur. I am not going to throw my kitty away, and I just would like to know what to expect if possible. Alternatively, if their is a thread I missed that covers this, please direct me. Thank you.