I first started Trelegy in January of this year and now notice that about 15 minutes after inhaling it, my heart will pound and flutter. It didn't do this at first, but maybe I just didn't notice it. It does go away after an hour or so. I have had extrasystoles since I was a teenager but I get them more now since I've been on this medication. I have not had any other issues with it. Since I also have severe panic disorder, this certainly doesn't help.