Cats and kittens with pulmonary or heart issues "pant" or have heavy breathing for no apparent reason or extreme lethargy that lasts for 30 minutes or more after minimal play. If you are playing with your kitten for 5 or 10 minutes and she starts the hard heavy breathing, it is something that needs to be checked. Cats have to REALLY exert themselves to get to the point they are panting. I don't want to worry you as I said, it's just something that is somewhat abnormal in cats. Unless they are very hot, or have been playing excessively hard, panting is something they just don't do....and after a drink of water and a couple of minutes of rest, if they are panting, it should stop by then.

Your kitten may be perfectly FINE, she may have a touch of bronchitis or asthma, but I would most definitely make your vet aware of the way she breathes so he can be more aware and spend a little longer listening to her heart for a possible murmur the next time you are in. I believe forwarned is forarmed and having possibilties laid out can only make you more aware and concientious. I know sometimes an expert will sugar coat things so as to not worry an owner, but I don't want people to totally brush off warning signs without having them checked out. Odds are that your baby is just fine, but I do think what you describe is worthy of being investigated the next time you take her into the vet. I don't think it's an emergency, but she should be going in for vaccinations in the next couple of weeks, so then would be a good time to talk this over with your vet. Another thought I just had was if you have a video camera and can catch her doing this on video, it can prove very helpful to the vet if you show the film to him when you go in.