Hello there. My name isXXXXX and I am very sorry to hear about Betsy and her fainting spells. Most likely they are not related to the dentastix unless she is swallowing large chunks of them that stimulate a response in her body called a vagal response that causes her to pass out. This would be extremely rare to have this occur but is not impossible. So at this point and time I would definitely stop giving her the chews for now. I would be very concerned that she may be having something going on with her heart causing this episode of fainting. So having her examined by your vet is very important to listen to her heart and check everything over to make sure that its not her heart or if it is evaluate what is going on and get her on meds to prevent any further issues like you have seen. There is nothing at home you can do for her heart except keep her in a quiet cool comfortable area that doesn't stress her out until you can have her checked out. And again don't let her have any more chew treats until this is all figured out. If it is her heart there are medications to make her feel better and prevent this in the future. At any point if she has any problems breathing or continues to pass out i would have her seen as soon as possible. I hope this helps. Please do not hesitate if you have any further questions or concerns. I would be happy to help. Please do not forget to rate my response so I receive credit for my time. Thank you!