Sinus tachycardia is [[Sinus_node_rhythms_and_arrhythmias|sinus rhythm]] with a rate of > 100bpm.
Sinus tachycardia is an example of a [[Supraventricular Rhythms|supraventricular rhythm]].
In sinus tachycardia the sinus node fires between 100 and 180 beats per minute, faster than normal. The maximal heart rate decreases with age from around 200 bpm to 140 bpm
. The maximal heart rate can be estimated by subtracting the age in years from 210. Sinus tachycardia normally has a gradual start and ending. Most often sinus tachycardia is caused by an increase in the body's demand for oxygen, such as during exercise, stress, infection, blood loss and hyperthyroidism. It can also express an effort of the heart to compensate for a reduced stroke volume, as occurs during cardiomyopathy.
The maximal heart rate is considered to be 220/min minus the age (or more precisely 207-0.7xAge <cite>Tanaka</cite><cite>Robergs</cite>). However, this is often exceeded during vigorous exercise and has a large inter-individual variation.