Pseudo-retrograde conduction in complete A-V heart block due to ectopic His bundle activity

A case with complete A-V heart block in whom retrograde P- waves following some of the ventricular complexes were due to an ectopic junctional activity with the characteristics of parasystole is reported. His bundle electrogram showed an infrahisian block. After administration of 1 mg atropine intravenously the retrograde P- waves were detached from the ventricular automatic complexes and an H' deflection preceded each inverted P- wave with an H'-A' interval of 40 msec.