Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.

In electrocardiography , the PR interval is the period , measured in milliseconds , that extends from the beginning of the P wave ( the onset of atrial depolarization ) until the beginning of the QRS complex ( the onset of ventricular depolarization ) ; it is normally between 120 and 200ms in duration . The PR interval is sometimes termed the PQ interval .
PR interval