Since your ECG and Echo were normal, this was definitely not a "heart attack". It was a Panic Attack in all likelihood. Nexito plus is a good drug combination but I don't think it will suffice in your case. You need a beta blocker as well. Please visit your Psychiatrist and tell him/ her about this event and ask him what the further course of action should be.
Next Steps
How long have you taken Nexito Plus? Did you discontinue after a month or two? If yes, then that could be a part of the problem.
Health Tips
In any case, get in touch with your Psychiatrist and let him/ her know about your Panic Attack and seek help.