Approximately 1 in 4 people will experience an anxiety disorder in their lifetime (Kessler, R. C., McGonagle, K.A., Zhao, S. et al. 1994), so it is likely you or someone you know will deal with one at some point or another.
One specific example of an anxiety disorder is Panic disorder. Panic disorder is characterized by recurrent and unexpected panic attacks.
Some common symptoms of Panic Disorder include physical symptoms that do usually proper reflect ones current situation. These can include, but are not limited to; shortness of breath, heavy sweating, tremors, numbness in hands, and pounding of the heart. The attacks generally take place at random, and for no reason.
People who suffer from panic attacks often complain that they feel they are dying when attacks occur. Often sufferers believe they are having a heart attack when a panic attack happens. It is usually a very unsettling event. I can attest to this, as I have had a panic attack myself, and truly thought there was something seriously, medically wrong with me in the moment.