Brief Answer:
Explained below.
Detailed Answer:
Hi XXXXXXX 
Welcome to Healthcare Magic!
You are having a 
panic attack if you experience an acute intense attack of anxiety accompanied by feelings of impending doom.The frequency of these attacks can vary from several attacks during one day to only a few attacks during a year.
In a typical panic attack, there is a discrete period of intense fear or discomfort, in which symptoms develop abruptly, reach a peak within 5 to 10 minutes and subside usually within an hour. The common symptoms are: 
1) palpitations, pounding heart, or accelerated 
heart rate 
2) sweating 
3) trembling or shaking 
4) sensations of 
shortness of breath or smothering 
5) feeling of choking 
6) 
chest pain or discomfort 
7) nausea or abdominal distress 
8) feeling dizzy, unsteady, lightheaded, or faint 
9) derealization (feelings of unreality) or 
depersonalization (being detached from oneself) 
10) fear of losing control or going crazy 
11) fear of dying 
12) numbness or 
tingling sensations 
13) chills or hot flushes 
Usually, someone who is having a panic attack for the first time feels that he is having a 
heart attack and goes to the emergency. It is only when he is seen by doctors and all tests come to be normal that he is told that he had a panic attack. When such attacks recur, one knows that these are panic attacks and takes appropriate treatment. 
Hope this clears up things for you. Let me know if you need any more information or any clarifications.
Best wishes.
Dr Preeti Parakh
MD Psychiatry