[Reentry tachycardia with complete atrioventricular dissociation probably connected with the right Mahaïm bundle]

A case of reentrant tachycardia with narrow and wide ventricular complexes without appearances of preexcitation is reported. Electrophysiological investigation showed complete retrograde atrioventricular block during tachycardia; left bundle branch block did not show the tachycardia rate. The reentry loop probably comprised: the His bundle, the right bundle branch, a right Mahaïm bundle and possibly a myocardial bridge. Possible intra-hisian reentry is discussed. The initiation of the tachycardia is analysed together with the possible consequences of permanent cardiac pacing.