In ortho- dromic AVRT (with anterograde conduction down the AV node), the P wave can usually be seen in the early part of the ST-T segment. In typical forms of AVNRT and AVRT, because the P wave is located closer to the prior QRS complex than the subsequent QRS complex, the tachycardias are referred to as having a short RP. They also have a 1:1 relationship between the P wave and QRS complex, except in rare cases of AVNRT in which 2:1 AV block or various degrees of AV block can occur. In unusual cases of AVNRT (such as fast-slow ), the P wave is closer to the subsequent QRS complex, providing a long RP. The RP is also long during an uncommon form of AVRT, referred to as the permanent form of junctional recip- rocating tachycardia (PJRT), in which an unusual accessory bypass tract with decremental (slowly conducting) retro- grade conduction during orthodromicAVRT produces delayed atrial activation and a long RP interval. A long RP interval is typical of AT because the rhythm is driven by the atrium and conducts normally to the ventricles. In AT, the ECG will typically show a P wave with a morphol- ogy that differs from sinus that is usually seen near the end of or shortly after the T wave (Figure 5). In sinus node reentry Figure 1. ECG showing AV dissociation during VT in a patient with a wide QRS complex tachycardia. *P waves are marked with arrows. AV indicates atrioventricular; ECG, electrocardio- gram; and VT, ventricular tachycardia. Reproduced with permis- sion from Blomstr m-Lundqvist et al.11 Page et al 2015 ACC/AHA/HRS SVT Guideline e515 tachycardia, a form of focal AT, the P-wave morphology is identical to the P wave in sinus rhythm. 2.4. 