It can be.  I have had severe panic attacks for at least 7 years now, and I have gone to the hospital on several occasions because I was having panic attacks, but thought it was a heartattack.  It can also make you feel tingly and numb, as well as making you dizzy and have headaches.  

Panic attacks usually do not last very long and for short duration most of the times. But hours is not an exception. It can occur for that duration. But first of all I would suggest you to get an ECG done and rule out cardiac ailments.