[Electrophysiologic study of paroxysmal supraventricular tachycardia].

Seventy patients (pts) with paroxysmal supraventricular tachycardia (PSVT) were examined by using electrophysiological techniques (EPS). At rest, 23 pts had the ECG evidence of W-P-W syndrome (group I) and 47 pts did not have (group II). In 20 pts of group I, PSVT could be induced by EPS. In 19 pts of them, the mechanism of PSVT was reentry using the accessory pathway (AP) retrogradely and the normal pathway (NP) antegradely, but only one showed the antidromic type (the former in reverse) of PSVT. Whereas in 45 pts of group II, PSVT could be induced reproduceably by EPS. In 31 pts of them, the mechanism of PSVT was reentry using concealed AP retrogradely and NP antegradely. In 13 pts, the mechanism was reentry within the AV node because dual pathways were found. In 11 pts, the reentrant beats conducted on the slow pathway (SP) antegradely, and on the fast pathway (FP) retrogradely. In 2 pts, reentrant beats conducted on the FP antegradely and on SP retrogradely. In one pt, PSVT was caused by sinus nodal or intraatrial reentry. Among 13 pts, in whom PSVT was caused by reentry using AP accompanied with dual pathways, the sudden change of the cycle length of PSVT were observed in 5 pts. PSVT which could only be induced by EPS in the laboratory were as follows: Af in 5, VT in 3 and sinus nodal reentrant tachycardia in one. In conclusion, in 65 pts of 70 pts with PSVT (93%), PSVT could be induced by EPS reproduceably. On the basis of EPS, the mechanism of PSVT was reentry involving AP in 29%, reentry involving concealed AP in 44%, AV nodal reentry in 19% and sinus nodal reentry in 1%.