How can you determine if my unexplained fainting is due to arrhythmia?

Event recorder: In order to be certain, a recording at the time is symptoms is necessary. Depending upon the frequency of the symptoms, there are different types of recorders/ monitors that are available.

Arrhythmia: There is a whole panoply of recording devices that can record cardiac rhythm for hours, days or even weeks to try and catch an arrhythmia.

Yes: Fainting had many causes, some could be related to arrhythmia ( fast or slow heart beats) or could be due to low blood pressure or other neurologic causes. Ask your doctor for event monitor if you have a recurrent unexplained fainting, this will try to correlate your fainting spells with any abnormality in the heart beats and then you can determine if arrhythmia is the cause of fainting.