[Paroxysmal junctional tachycardia. Determination of the inferior point of junction of the reentry circuit. Dissociation of the intra-nodal reciprocal rhythms].

Stimulation of the bundle of His and of the uppermost portion of the interventricular septum gives us an opportunity to make a precise study of capture phenomena in patients with paroxysmal nodal tachycardia. According to whether the capture is correctly timed, delayed, or unusually premature, the inferior junction point of the reentry circuit can be located precisely by reference to the H wave and the onset of the R wave. Out of a series of 65 patients, only 30 of whom had a true WPW syndrome, it was shown that 43 cases had a bundle of Kent which ensured retrograde conduction during the tachycardia, and was therefore the seat of a unidirectional block in 13 cases. In 22 cases (33.8%) the diagnosis of WPW syndrome was excluded, but the reentry circuit was nevertheless not of nodal origin. The inferior junction point of the circuit was effectively situated between H and R in 12 cases, and at H in 5. In only 5 cases (7.8%) might there have been a reciprocal intra-nodal rhythm, which should not necessarily be taken as proof of its existence. The validity of the classical criteria in localising the reentry circuit is discussed.