What is the diagnosis of palpitations? A case report of rate-dependent
retrograde conduction over an accessory pathway
Introduction: The phenomenon of intermittent retrograde conduction over
an accessory pathway (AP) is very rare. Methods: We report a case of
AVRT without ventricular pre-excitation and arrhythmia recorded.
Stepwise decremental pacing was delivered from RV apex. When the pacing
CL was shortened to 400 ms, Retrograde ventriculoatrial (V-A)
Wenckebach-type block appeard with the earliest atrial activation at the
ostium of CS. The S1S2 interval was first set to 450ms and then reduced
by 10ms and atrial-ventricular node ERP (AVNERP) occurred at
500ms/410ms. Results: Retrograde conduction over an AP was present only
during ventricular pacing with a fast pacing rate (S1S1 300ms, S1S2
500ms/290ms) and narrow QRS tachycardia was induced by atrial programmed
stimulation. The AP was ablated successfully in the end. Conclusion: It
is suggested that careful evaluation by EPS should be applied during
baseline study, especially in the case without arrhythmia recorded.