Complete Atrioventricular Block with Intact Retrograde Conduction in Cardiac Rhythm Management Devices: Implications of the Phenomenon.

Intact retrograde ventriculoatrial (VA) conduction in the presence of complete atrioventricular (AV) heart block has been well-documented in the past. We sought to describe the prevalence and clinical significance of intact VA conduction accompanied by complete antegrade AV block in patients with implanted cardiac rhythm management (CRM) devices. During routine follow-up of CRM devices in our device clinic, 42 patients were found to be in a state of complete heart block. All patients presented in sinus rhythm. The patients' underlying rhythms were tested with the inhibition of pacing and documented AV dissociation. Subsequently, retrograde VA conduction was tested with ventricular pacing. In the 42 patients with complete heart block as the underlying rhythm, five patients demonstrated retrograde VA conduction. In conclusion, the prevalence of intact of VA conduction was 11.9% in our study. The implications of this phenomenon can have noteworthy clinical significance. The occurrence of pacemaker-mediated tachycardia and repetitive nonreentrant VA synchrony are discussed herein. All patients, even those with a device indication of complete heart block, should be tested for retrograde conduction at implantation and during routine follow-up.