I see from a previous post that you like to jog so you're into keeping fit so please see a doctor amd then let us know that structurally everything is OK then we can start to look at other things
look after yourself
dave
If you can not find a doctor, then, I would sure go to the ER and have them check some things, such as your thyroid levels, the synthriod could be giving you too much thyroid hormones causing an over active thyroid and this in turn could be causing the palps. Also, they will probably run an EKG on you and some other diagnostic tests. I really think you should check it out, blacking out for even short periods is nothing to play with. The Thyroid gland is tricky to get adjusted, and you may very well need some medication adjustments also.
Keep us posted.