I was doing 300 lb bench presses for three sets before my surgery. Had to wait about 9 months after my surgery to lift again, but now bench 180 lb for 4-5 sets. The weight seems light to me, but that's relative to what I was doing before. I'm just trying to stay toned, not get any bigger at this point.
One change I made is that I now do at least 30 minutes at day on the treadmill or stationary bike and on days I don't get to the gym, I run 1 -2 miles.
Every one is different, which is why you need your doctor's advice before starting any post-op exercise. My doctor is okay with my program - but he did have me give up leg presses and squats.
Regarding Arnold, I believe he actually blew his valve out on a stationary bike a couple of days after his first surgery, not lifting weights.
Mark