Areas of slow conduction in atrial re-entrant tachycardia: a case report and review of the literature.

An electrophysiologic study of atrial tachycardia is presented. During tachycardia, transient entrainment and sinus rhythm, two patterns of persistent double potentials in the high right atrium and fragmented activity in the low atrial septum were observed. No activity was recorded from multiple areas of the right atrium with endocardial mapping during sinus rhythm. The observations suggest that persistent fragmented activity represents slow conduction within the circuit which could be orthodromically entrained. Persistent double potentials probably represent slow conduction orthodromically and/or antidromically activated outside the circuit. However, a wave front from pacing impulses travelling through this area could entrain the circuit.