Tachycardia comes from the Greek words tachys (rapid ) and kardia (of the heart). Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate (heart rate in an inactive or sleeping individual). It can be dangerous depending on the speed and type of rhythm. A healthy adult heart normally beats 60 to 100 times a minute when a person is at rest. If you have tachycardia, the rate in the upper chambers or lower chambers of the heart, or both, are increased significantly. Heart rate is controlled by electrical signals sent across heart tissues. Tachycardia occurs when an abnormality in the heart produces rapid electrical signals. In some cases, tachycardias may cause no symptoms or complications. However, tachycardias can seriously disrupt normal heart fun