FPS Inconsistency

For some reason when playing my frame rate will drop into the single digit or teens range and then go back between 50-70 fps. I don't have this issue with any other game on my PC. Changing the graphics setting from high to med, then med to low made no difference. With my current setup I am usually able to run games at their highest setting with no issues. Wondering if anyone else is experiencing the same thing.

What graphics card do you have?