Overview
Heart palpitations (pal-pih-TAY-shuns) are the feelings of having a fast-beating, fluttering or pounding heart. Stress, exercise, medication or, rarely, a medical condition can trigger them.
Although heart palpitations can be worrisome, they're usually harmless. In rare cases, they can be a symptom of a more serious heart condition, such as an irregular heartbeat (arrhythmia), that might require treatment.
Source: http://www.mayoclinic.com