[The mechanism of the chronic supraventricular tachycardia: an intracavitary electrophysiological study (author's transl)].

Chronic Supraventricular Tachycardia (CST) or Chronic Atrial Tachycardia is a relatively rare arrhythmia. Because of very poor number of cases studied with electrophysiologic techniques its mechanism is still debated. Three cases of CST, one of persistent type and two of repetitive type, are reported. His bundle electrogram, high and low right atrial electrograms and atrial stimulation were performed in every case, ventricular stimulation in only one case. The Amiodarone, Pindolol, Verapamil and vagal manoeuvres effects were evaluated in all cases. The site of origin of tachycardia, atrial in cases 1 and 3 and junctional in case 2, was estabished by atrial map. The electrophysiologic findings suggested the presence of an ectopic focus in cases 1 and 3 and of an AV nodal re-entry circuit in case 2. Our results and those of the literature indicate that the site and the mechanism of CST, as in paroxysmal supraventricular tachycardia, is not univocal. Their electrophysiologic evaluation by means of endocavitary techniques can allow a more satisfactory therapeutic approach.