When you're doing an EKG experiment and suddenly see higher amount of bpm than usual, in your Spike Recorder, don't worry. All you have to do to get a proper reading is to click on the Threshold button and move the bar upwards.
That way your bpm will be normal and you can continue your study. Also within the manual you've received your Heart&Brain SpikerBox  with, their should be an explanation about how to stabilize the bpm rate and get a proper reading.