I Have A Mechanical Mitral Heart Valve And Have Been

I have a mechanical mitral heart valve and have been taking warfarin, aspirin, Effexor, Diltiazem and Amiodarone since the surgery 12 years ago. I've had to start taking Crestor since last August and now my atrial fibrillations came back quite strongly. My cardiologist cancelled Amidarone, increased Diltiazem and addedDigoxin (0.125mg) The fibrillation are a bit weaker, but it still bothers me a lot. 3 days ago I stopped taking Crestor and it seems already better. Is there an alternative drug that can be taken that doesn't have the a.fibrillation effect?