Browse the corpus

©2013 UpToDate ® Print Email Conduction through an accessory pathway with AV nodal delay Compared to conduction through an AP with normal AV node conduction, delayed conduction through the AV node allows more of the ventricular myocardium to be activated by preexcitation (shown in blue). The inset on the right shows the ECG timing of these events. The atrial to His interval is increased due to the AV nodal delay (RA to H); His activation is so delayed that is follows activation caused by the AP (V P ). The PR interval is short due to the preexcitation, the delta wave (arrow) is more pronounced due to the greater and unopposed early forces (blue), and the QRS duration is prolonged due to the later than normal ventricular activation caused by the AV nodal delay (yellow).