Simultaneous antegrade dual AV node conduction initiates AV nodal re-entrant tachycardia [a rare initiation mechanism]

Typical atrioventricular nodal reentrant tachycardia [AVNRT] is the most common paroxysmal supraventricular tachycardia among adults. The concept of dual pathway physiology remains widely accepted, although this physiology likely results from the functional properties of anisotropic tissue within the triangle of Koch, rather than anatomically distinct tracts of conduction. AVNRT is typically induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. On rare occasions, anterograde AV node conduction occurs simultaneously through fast and slow pathways resulting in two ventricular beats in response to one atrial beat. We report a case of AVNRT where the tachycardia is always induced by the same mechanism described above. Successful ablation was achieved by slow pathway modification

practical approach to discerning between atrial lead displacement and reversal in dual chamber pacemakers

We describe a 12-lead electrocardiogram image of a pacemaker malfunction due to atrial lead displacement. Facilitating the understanding of pacemaker timing cycles could explain the underlying mechanisms in this instance. This review utilizes the feature of the ventricular safety pacing interval to discern between atrial lead displacement and reversal