Sustained intra-atrial reentrant tachycardia. Electrophysiologic study of 20 cases

Twenty cases of sustained tachycardia due to intra-atrial reentry were investigated in patients aged 17 to 80 years (mean 47). The average frequency of the tachycardia was 128.6/min (extremes 95 and 180). Three modes of onset of the tachycardia were observed: atrial extra-stimulus (19 times), progressively accelerated atrial pacing (9 times) and atrial escape beat (10 times). The tachycardia was stopped in all cases by a premature stimulation. When spontaneous, the termination was either sudden (10 times) or preceded by a progressive slowing (9 times) or an alternating phenomenon of long-short cycle (13 times). Precise atrial mapping allowed to localize the first atrial depolarization less frequently in the sinus node area (1 case) than in the mean right atrium (21 cases), the low right atrium (2 cases), the interatrial septum (2 cases), and the left atrium (4 cases). The macroscopic size of the reentry circuit was demonstrated in only 3 cases. A junctional reentry was accurately ruled out in all cases thanks to the existence of a second or third-degree AV or VA black, or by studying the sequence of retrograde atrial activation. A true junctional reciprocating tachycardia was associated with the intra-atrial reentry in 2 cases.