I suffered from panic attacks and anxiety for years, and went untreated. During that time, anything that increases heart rate, breathing rate, etc, would get me nervous (such as 8 cups of coffee every morning for 9 months, while getting less than 6 hours of alcohol induced sleep everynight, and eating food that contained more sodium than protein). The old CAE stack used to get me spacey and nervous also.
Anyway, I eventually started Paxil and was able to get with life. I now pop Paxil and Wellbutrin, and the Panic is not a factor anymore (99% of the time). After 8 years of dealing with this, I can say that it does help to get a rational understanding of the process (not event) of Panic. It allows me to absorb things like faster heartbeat without getting nervous.
BTW, I suffered from SVT (supra-ventricular tachycardia) before the Panic started, and I'm sure that was a major catalyst. Interesting to hear others had heart issues leading to anxiety also.
My advice. Seek medical attention. Doctors are good about helping anxiety these days. If you would rather not pop pills, try massage and herbs. I can't overemphasize how much massage helped me. Herbs such as kava kava and valerian root have been effective for me. Avoid caffine and recreational drugs, and get enough sleep.
And most of all, realize that it is just your body reacting to a perception. You are not going "crazy" or "losing it". You are not going to die, and the panic WILL pass. Just breathe deep, and try to understand the physical processes that are occuring.