Does your heart occasionally flutter or skip a beat? Does it pound unusually fast or unusually slow? If so, you may have a cardiac arrhythmia, an irregular or abnormal heartbeat that indicates a malfunction in the heart’s electrical system. An arrhythmia may be no big deal—causing no symptoms, sometimes, and presenting no underlying damage or disease - or it could be a very big deal indeed, possibly leading to stroke or sudden cardiac death.