please get blood enzymes checked, my sis had heart attack and stroke after feeling like that and had to have a triple bypass!
Regarding Lopressor. The generic name for this drug is Metoprolol. It is widely prescribed and easily tolerated. I would not fear taking this medication. Like myself, many of us here are on It and have been so for years.
Regarding your episodes. It may be very possible that you experienced PAT. It's also possible that you had an SVT episode. In each case, Valsalva is often effective in converting it. In most cases, these episodes are not life threatening. Along with my 50mg 2x/day dose of Lopressor (metoprolol), my GP told me to chew an extra dose when an SVT episode occured. I did this often, but my cardiologist informed me that itnprobably did little to help convert the SVT, and that it wouldn't work that quickly. I believe you need to take this on a daily basis for it to be effective.
If this becomes a common event, you should consult with a cardiologist. A 30 day wearable 2 lead recorder stands a better chance of capturing an event than a 24 HR. Holter. Hope everything works out for you!