I would be more concerned about the pacemaker and martial arts than I would be about warfarin and martial arts. I have never taken up martial arts, but I wouldn't hesitate doing so just because of warfarin. Of course, there are numerous forms of martial arts.
This isn't quite the same, but somewhat similar: a 16YO young man I know is going out for football this fall. He was DXed with diabetes 5 years ago and has been using an insulin pump. A week ago he got an Omnipod, a device that will administer the insulin and which offers advantages over an insulin pump. (A year ago, the teen jumped into a swimming pool while on vacation without taking off the insulin pump, which fried the pump's computer. A new computer had to be overnighted.) I don't know how the Omnipod will fare during a tackle, which is not unlike wondering how a pacemaker will handle if you take any kind of blow in the chest.
Marsha (7-28-50), MVP 1990/MVR (St. Jude) & ASD repair 6/24/03 Baylor University Medical Center, Dallas Texas. Hometesting since 11/03, first with ProTime 3, now with INRatio.
John (3-13-46), MV repair 5/10/07, Dallas Presbyterian, port-access incision, Dr. William Ryan. Chordae ruptured 12/05 in car crash.