I am a 53 yr. old woman who had aortic Valve replacement surgery ...

I am a 53 yr. old woman who had aortic Valve replacement surgery in April 2007. I had a St. Jude valve put in and have been on Warfarin ever since. I usually go for a couple months with a steady INR and then, for no apparent reason, it goes out of whack and I have to adjust the level (with repeated doctor visits) to smooth things out. I have gained 20 lbs since my surgery, and cannot lose it, no matter what I do! I ride an exercise bike an hour a day, or walk a 3 mile route. NOTHING helps. I have recently said that if I had it to do all over again, I would choose a Bovine valve (even with the knowledge that surgery would probably have to be repeated later in life) just to be able to avoid the side effects of Warfarin. I have also experienced light-headedness, left sided chest pain, fatigue, coarse thinning hair, but by far, the worst is the weight gain!!