206: Isoproterenol infusion is more frequently required for the induction of atrioventricular node reentrant tachycardia than for the induction of atrioventricular reentrant tachycardia

Supraventricular reentrant tachycardia (SVT) can be due to atrioventricular node reentrant tachycardia (AVNRT) or atrioventricular reentrant tachycardia (AVRT) in a concealed or an overt accessory pathway (AP) in patients with a Wolff-Parkinson-White syndrome (WPW). The purpose of the study was to look for the mode of SVT induction and to correlate the mode of induction with the mechanism of the tachycardia.Methods1818 patients were consecutively referred for a SVT. 438 had a WPW (group I). Remaining patients had a normal ECG. At electrophysiological study (EPS), SVT was related to AVRT in 251 patients (group II), to typical AVNRT in 969 patients (group II) and to atypical AVNRT in 160 patients (group IV). Atrial pacing and programmed atrial stimulation with one and 2 extrastimuli were performed in control state (CS). If SVT was not induced, the protocol was repeated after isoproterenol (0.02 to 1 μg. min-1) infused to increase sinus rate to at least 130bpm.ResultsGroups differed by age and gender: group I was younger than group II (36±17 vs 42±17 years) (p < 0.001). Group II was younger than group III (49±19)(p <0.001) and group III was younger than group IV (55±19) (p < 0.001). Gender in group I and II was more frequently male (55%, 57%) than in group III (36%) and IV (36%)(p<0.000). SVT induction required more frequently isoproterenol infusion among patients of group III with a typical AVNRT (32%) and IV with atypical AVNRT (33%) than in patients of group I (26%)(p<0.05) or group II (24%) (p < 0.02). Men required more frequently isoproterenol than women only in group I (p<0.0001). The youngest patients required more frequently isoproterenol than other but the differences were only significant in group III (47±19 vs 51±9 years, p