Panic attacks, along with the sense of impending doom, walls closing in, shortness of breath, and chest pressure, also include palpitations, which is due to the excessive sympathetic response (flight
or fight) due to adrenaline in
the blood. The palpitations can be just due to the heart
beating stronger from the increased stimulation, or can actually be abnormal beats caused by the adrenaline over stimulating heart cells which then activate early or abnormally.