So. Maybe I'll start this post by saying, I'm a brand new vet (i.e., knowledge but not much experience). I also talk too much.
The way a murmur sounds has absolutely no correlation with the severity of the problem in the heart. A very very very mild leak of blood around the valves that has no clinical significance might sound very loud because it's a thin, strong stream of turbulence. A major problem, with the valves almost not closing at all, might have no murmur or a very mild murmur, because there's no blood flow, so no turbulence. Turbulence of blood is what makes the sound of a murmur.
Both my chinchillas have a heart murmur. I found it on one when I stuck my stethoscope on Jacques one day just for the heck of it.
Took him in to school, had a couple of the exotics residents listen. Yep, it's a murmur. This coming from people who work with a lot of exotics, including chinchillas, on a regular basis. Chinchilla heart rates are not as high as you'd expect from a rodent, so it's actually pretty easy to listen to their hearts. The trick is, though, is to not use much pressure, because you can, apparently, induce false murmurs. It's all in the technique.
Month or so later, I brought both boys in for a thorough physical, bloodwork, and skull and whole body radiographs just for the heck of it (well, really to make sure that neither had anything going on I would want to know about and deal with before I graduated and lost my student discount). I got an appointment with cardiology for Jacques.
Jacques' murmur was confirmed by the cardiologists. They did an echocardiogram (ultrasound of the heart). What they found was an extremely mild leakage of blood around one of the valves. They were concerned because subjectively, the heart muscle looked thick to them. They asked to see Ravel to compare with a "normal." They found a very quiet murmur, previously unnoticed by me or two exotics vets in him as well. They did an echo, found that his heart looked very similar, and that his murmur was coming from almost the same problem.
There is a paper published on chinchilla heart measurements, so they went to look that up, and it turns out, both my boys are within normal ranges.
So. What does this all mean? I spoke at length with the cardiologist about this. According to them, what Ravel and Jacques has is not uncommon in cats. In a cat, it is an extremely rare case when that particular type of murmur ever causes a problem or even gets worse. It tends to be very static. It is not thought to be heritable. They would not counsel a breeder against breeding an animal with this particular type of murmur. They would simply say, "this cat has this kind of murmur with this type of leakage around the valves, unlikely to be of any significance. If two animals were identical in every other way except for the murmur, then probably breed the one without the murmur, but we wouldn't counsel a breeder against breeding a cat because of this particular murmur." Given that these were chinchillas and they haven't studied them as intensively, they don't know. Their advice was, monitor the murmurs, have a cardiologist look at them if it ever changes. So I plan to listen to them every few months. [to be a little more clear, there are heart problems that cause murmurs that are heritable, but in the cat, this is not one of them.]
I then went online to what's essentially a web forum for veterinarians and asked questions. The head of the exotics department at another vet school was of the opinion that he had had very few chinchillas with actual murmurs (he feels that most chins referred in that he's seen with murmurs had false murmurs that were induced by auscultation technique), and those few that have had verified murmurs have later proven to not have a significant problem (I don't have access to the board right now, since it's a paid site, but I seem to recall him saying less than 6 or so in the 10+ years he's been seeing chins). This would be the same person who published the paper on normal chinchilla hearts. Given the number of people with the amount of combined experience involved, I think that both murmurs in my boys are real, but not clinically significant.
So. Where does this get us? It is of the opinion of the veterinary community that I have access to that chinchillas rarely have significant heart disease, even though a goodly number may be diagnosed with murmurs.
