[Tachycardia caused by sinus-node and atrial re-entry with associated depression of A-V conduction]

The authors report two clinical cases (one with WPW syndrome) of paroxysmal supraventricular tachycardia caused, in one case, by sino-atrial node or perisinusal nodal tissue re-entrance and in the other case by re-entry in the lower atrium and the high part of the A-V node junction. Both present A-V node Wenckebach periodism, which can be distinct from reciprocating tachycardias, through an anomalous pathway or within the A-V node, which have a typical A-V conduction in the ratio of one to one. But A-V node Wenckebach periodism makes it hard to differentiate between reciprocating and ectopic atrial tachycardias, as the latter often has an A-V block. The effects of two antiarrhythmic drugs (Verapamil, Amiodarone) on echo-zone duration, on initiation and on prophylactic long-term treatment of paroxysmal tachycardias are also reported and discussed.