AV nodal reentry is a form of SVT that establishes its atrioventricular circuit entirely within the AV node. The heart rate is usually regular, between 150 to 250 bpm (below = 186 bpm). The QRS complex is narrow with a duration less than 0.2 seconds and a conduction ratio of 1:1. P waves are buried within the QRS compelx (as illustrated below), although they may be visible at the end of the complex as a distortion of the terminal forces. Due to the fact that atrial activation originates from the inferior aspect of the right atrium, P wave polarity is negative in leads II, III and aVF. This form of SVT is usually benign and is easily converted to sinus rhythm by vagal maneuvers.