Ativan's a potent anti-anxiety med. Perhaps that was your first high anxiety attack. Have you had earlier periods of feeling generally anxious, perhaps to the point of it sometimes affecting your quality of life?
Did you start smoking as an adult (~age 24)? Had you just stopped smoking (again) prior to this episode? Discontinuing nicotine abruptly can greatly heighten nervous tension and trigger anxiety, perhaps severe anxiety when combined with some other stressor such as a social setting, in anyone predisposed that way and untrained in coping methods.
A supervised treadmill stress test (where you're hooked up to an ECG), would help uncover any heart defects you may be contending with [that ought not be extraordinarily expensive, less than the actual cost for an ambulance ride in most areas imo]. A resting ECG merely records the heart's activity at rest and without any challenges.
I suspect a high anxiety episode may have been stressing your heart in such a way as to expose a heart defect.
Yes, I started smoking as an adult, quit for a few years and started again. I had very recently quit smoking but switched to an ecig before the episode.
I've been under stress lately (moving, car wreck, financial. Etc.) but Ive never had an "anxiety attack". Never been on meds but I do use marijuana. Medical card holder in the state of Colorado. I've never had adverse reactions to marijuana or any other drug.
I am extremely sensitive to caffeine and hardly used it anyway.
It's weird because I stayed very calm and never thought I was panicking, until I started tracking my heart rate and having spasms.
Thanks for the input, I was thinking about an ultrasound of my heart and I will look into the stress ecg.