Diagnosis and Ablation of Long RP Supraventricular Tachycardias.

OPINION STATEMENT: Long RP tachycardias are a unique collection of arrhythmias that include atypical (fast-slow) atrio-ventricular nodal reentrant tachycardia (AVNRT) with and without a concealed, bystander nodo-fascicular/ventricular accessory pathway (AP), orthodromic reciprocating tachycardia (ORT) using a concealed, slowly conducting, and decremental atrio-ventricular (AV) AP (PJRT), ORT using a concealed nodo-fascicular/ventricular AP (NFRT), and atrial tachycardia (AT)-all but the last being dependent upon the AV node. These tachycardias respond differently to pacing maneuvers than their short RP counterparts and can manifest: (1) both true and pseudo-AAV responses, (2) long uncorrected and corrected post-pacing intervals, (3) prolonged delta ventriculo-atrial (∆VA) and delta His bundle-atrial (∆HA) values, and (4) resetting with delay. Diagnosis requires analysis of available clues from spontaneous transition zones as well as atrial and ventricular pacing maneuvers to delineate the upper and lower limbs of each circuit, respectively. Establishing the exact mechanism of tachycardia is important for safe and successful ablation. With activation mapping to localize AT or the AV AP of ORT and slow pathway (SP) ablation of atypical AVNRT and NF APs inserting into the SP, the majority of long RP tachycardias can be successfully treated.