DD2 has a stridor which has been obvious since about 8 weeks (which is when they are often first noticed). I'm not sure how many things can cause a stridor but in our case it is caused by some floppy muscles in/around her larynx. It is the kind of thing which over time the muscles get stronger and they grow out of it, a bit like reflux babies get more mature stomach muscles and the reflux calms down and kids ear canals mature and ear infections stop occuring.
Hope your appointment went well.