I have had BMP taken which included magnesium and potassium within the last year, and all levels were normal, and at least once a year before that. I have an echocardiogram coming up, but they have all improved over the years. Fatigue and endurance was very bad when I was first diagnosed, (I couldn't even go up a flight of stairs without stopping to rest, now a flight of stairs is no problem.) but have improved since then. I will ask my cardiologists about these other medications that you have suggested. Understand that I have been dealing with this problem for about 8 or 9 years, and have been improving, but it is only within the last year that I have attempted to restart playing the trumpet and discovered a possible problem.