I did not have antibiotics with my last colonoscopy but I did not have my valve either … My gastro (he is for now anyway) was in the dealership this week and I was talking to him about ACT and he asked me which position my valve was in and I told him aortic and he said that the aortic is not a critical for throwing clots as the mitral and if I had a mechanical mitral he would put me in the hospital to bridge …. Anyone ever heard this? … Is it true … I have not had to come off warfarin since my surgery and I need to have a colonoscopy and I will tell you this thing freaks me out … so many different opinions … here and from medical professionals.