Sinus tachycardia is a heart rate greater than 100 beats per minute. The electrical impulses that cause the heart to beat come from the normal "pacemaker" of the heart.
This condition is a fast heartbeat that is not a true or primary arrhythmia, which is an abnormal heartbeat. Instead, it is a normal response to demands on the heart. The heart beats regularly in this condition, but faster than normal. This condition generally starts and stops gradually, such as at the beginning and end of exercise.
There are many possible causes of this condition, including: