Abnormal heart rhythm is a medical condition that refers to any irregularity in the beating pattern of the heart. There are various synonyms for this condition such as cardiac arrhythmia, irregular heartbeat, and dysrhythmia. Cardiac arrhythmia is a term used to describe any abnormality in the electrical activity of the heart that leads to an irregular heartbeat. Irregular heartbeat is a broad term that refers to any deviation from the normal rhythmic pattern of the heart. Dysrhythmia is a medical term used to describe any deviation from the normal sinus rhythm. These terms may be used interchangeably to refer to the same condition of abnormal heart rhythm.