[Tachycardia caused by reciprocal rhythm between normal pathways and a rapid atrial-His pathway]

Report of one unhabitual case of reciprocal rhythm with anterograde conduction through James' fibres and retrograde conduction through the normal nodal pathways. The reality of an anterograde nodal short-circuit is indicated by many arguments, and in particular by the presence of a double ventricular response, after induced atrial premature beats reaching the ventricle once by the rapid pathway and the second time by the slow pathway.