title: Paradoxical increase of stimulus to atrium interval despite His-bundle capture during para-Hisian pacing.
abstract: Para-Hisian pacing at high output simultaneously captures the His bundle or proximal right bundle, as well as the adjacent ventricular myocardium. At lower output, direct His-bundle, or right-bundle, capture is lost which causes an increase in the stimulus to atrium interval. We describe a case with an increment of 68 ms with capture of the His bundle. This seems to be a paradoxical response, which however can be explained by the presence of retrograde dual AV-node physiology. Continuation of this phenomenon could be related to concealed anterograde invasion of the fast pathway thereby maintaining the retrograde activation during para-Hisian pacing on the slow pathway despite paced cycle lengths (His to His intervals) where retrograde fast pathway conduction proved to be possible.
authors.affiliation: Department of Cardiology, Maastricht University Medical Centre, Maastricht, The Netherlands. jmvanopstal@yahoo.com
authors.forename: Jurren M
authors.initials: JM
authors.lastname: van Opstal
authors.forename: Harry J G M
authors.initials: HJ
authors.lastname: Crijns
mesh_terms: D000328:Adult; D002036:Bundle of His; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria; D006333:Heart Failure / Q000517:prevention & control*; D006801:Humans