Introduction: Symptomatic sustained slow AV nodal pathway conduction during normal sinus rhythm in patients with dual AV nodal physiology is not known well. Methods: Among the patients presented with chest fluttering and prolonged PR interval, 10 patients with two distinct (short and long) sets of PR interval during normal sinus rhythm were selected. Of the 10 patients (male: 5, age: 36 짹 12 years), 4 underwent electrophysiologic study (EPS) and radiofrequency ablation of slow pathway. Their electrophysiologic characteristics were analyzed. Results: Patients had slow chest fluttering mainly at resting state or on mild exercise. The rhythm was misinterpreted as accelerated junctional rhythm by referring physicians. Two distinct sets of PR interval or transition between short and long PR interval in normal sinus rhythm were documented on 12 lead ECGs and/or Holter monitoring. The difference of two sets of PR interval was greater than 150 ms, and extreme PR prolongation with P on T phenomenon was a characteristic ECG finding. Mean values of short and long PR interval were 178 짹 35 vs. 455 짹 100 ms (p < 0.001), respectively. Main electrophysiologic characteristics of sustained slow AV nodal pathway conduction were poor antegrade fast pathway conduction property and VA dissociation. Of the 4 patients who underwent EPS, dual AV nodal physiology was demonstrated by AH jump in 3. Sustained slow AV nodal pathway conduction was reliably induced by programmed electrical stimulation in the 3 patients. After slow pathway ablation by conventional posterior approach, all the 4 patients remained asymptomatic without recurrence of slow pathway conduction. Conclusion: Intermittent symptomatic sustained slow pathway conduction is rare but highly symptomatic, often simulating accelerated junctional rhythm. Radiofrequency ablation of slow pathway may be an optimal therapeutic option. Key words: Dual atrioventricular nodal physiology, Slow pathway, Radiofrequency ablation