[Diagnosis of the mechanism of reciprocating tachycardia by a simplified electrophysiological study].

The authors attempted to identify the parameters which best differentiated intranodal reentry from tachycardias associated with an accessory pathway during a simplified electrophysiological study. The data were obtained by using two catheters, one recording right atrial activity and the other delivering programmed stimulation in the right ventricle. Sixty-four patients in whom the mechanism of their tachycardias had previously been determined were studied. There were 19 intranodal and 45 accessory pathway tachycardias. The following parameters were studied: the ventriculo-atrial interval during tachycardia; the prematurity of atrial activity in response to programmed ventricular stimulation; the shortest ventriculo-atrial interval when the atrial activity was premature; the difference between the shortest ventriculo-atrial interval with atrial prematurity and the ventriculo-atrial interval during tachycardia; in the absence of prematurity the ventriculo-atrial interval with the shortest ventricular coupling was used. The ventriculo-atrial interval during tachycardia was shorter in intranodal reentry (43 ms vs 170 ms, p less than 0.001). This interval was greater than 120 ms only in accessory pathway tachycardias and was only under 75 ms in patients with intranodal tachycardias. Premature atrial activation was observed in 42% of intranodal and 98% of accessory pathway tachycardias (p less than 0.001). The predictive value for tachycardias involving an accessory pathway was 85% when the auriculogramme was premature and, conversely, it was 92% for intranodal tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)