I Am On Warfarin For The Last 10yrs With An

I am on Warfarin for the last 10yrs with an avage dose of 26 to 35mgs per week to maintain INR between 2.0 t0 2.50. I am 83 yr.old with implanted CRT-D (2nd). lately wafarin is showing irretic results with the same dose. can I change-over to Acetrome-2, if ok what is the ideal dose to maitain INR between 2.0 and 3.0 or what is an alternative.