Rebecca, when "murmur" is used it's valves, I think (CHECK ME because I am NOT sure), BUT I don't know if not losing those fetal blood vessels or having a fetal-type of vascular overlay creates any noises which might sound similar. In such a case the ferret would often be having the blood inadequately aerated and there are other possible serious problems. For those who are curious: neural crest mutations don't usually seem to affect the heart but since the rate of cardiac crest malformations is higher in them it can do so (and also the rate is impossible to know because almost no one necropsies dead infant kits or failed fetal ferrets so it could be more than thought -- not likely to be fewer). Those sorts of malformations include vessels which are in a fetal path that it is just plain wrong for the fully formed heart and lungs, or not losing some fetal heart blood vessels which need to be lost for the heart and lungs to operate properly for survival out of the uterus. Most of these individuals die in-utero OR die as infants (which is possibly one reason that among a number of breeders the tragedy of lost kits of neural crest disorder ferrets amounts to so very many avoidable deaths (as in a recent case in which the female has had at least 17 kits born (if memory serves) in multiple litters but so far only a scant handful kits have survived just part of early infancy and who knows so far if those will make it), and is one reason that many consider it a terrible and cruel choice to breed such ferrets, especially coupled with the damage neural crest disorders can do to the intestines, jaw, hearing, life-expectancy, etc.). Also, neural crest disorder ferret females often have enough hearing loss that it impacts badly on their infant care; they just can't use the valuable tricks which non-hearing human parents can use. Blazes, pandas, and other neural crest malformation ferrets just plain should not be bred. It is unfair. Neural Crest mutations cause changes to a very early cell type which later develops into a large range of widely located cells with an assortment of functions. The expression of these mutations is variable, which means that the mutation itself is constant as it is passed through the generations but how strongly it expresses itself varies, so while one individual may be okay or mostly okay the child or grandchild may have major health problems to struggle through throughout life and in ferrets they may have greatly shortened lives. I realize that people have bred such ferrets BEFORE there was so much information, and that some have bred then without knowing these things and those people simple didn't know. The ones who breed knowing these things and who breed despite high death rates do worry me, though, because quite simply I can't figure out any reasonable reason for them to have done so once they know and begin to read the warnings out there including from geneticists that there are no safe variants known among ferrets and there is no way to modify any of the the neural crest disorders to be safe, and that ferrets with the markings should be sterilized. (BTW, because of mutations, but far more often because of variable expression, it is possible to have a ferret who appears normal but carries one or more of these mutations. It is also possible to have an individual who has several neural crest mutations simultaneously because there are multiple loci (genetic locations) which can harbor mutated alleles that cause them.) [Posted in FML issue 4520]