Incessant Narrow Complex Tachycardia
Incessant NCT in a 6-year old boy. ECG shows initiation of tachycardia after a few sinus beats:
After the fourth beat of sinus rhythm a premature atrial contraction (PAC) appears showing inferior P-wave axis (negative in II/III/aVF) and initiates narrow complex tachycardia. Tachycardia shows long R-P interval (RP > PR).
This is typical for permanent junctional reciprocating tachycardia (PJRT), typically showing inferior P-wave axis, long RP interval, and incessant nature. PJRT is also known as Coumel type tachycardia, based on an mostly septal accessory pathway with pure retrograde conduction and decremental conduction properties.
Medical treatment may be difficult. Class I antiarrhythmics, sotalol or amiodarone may be used. Electrophysiological study and ablation is the therapy of choice.