On Some Nights I Have Bad Arrhythmias Lasting 8 Hours.

On some nights I have bad arrhythmias lasting 8 hours. I can hardly walk to the bathroom and am short of breath. On other nights I don't have arrhythmias and I feel fine in the morning. I had a heart stress test on a day that I felt fine and the LVEF was 60%, normal. If I had the stress test during an arrhythmia episode, when I can hardly walk, how would the LVEF be affected? Might it drop to 45%? Thank you.