Noninducibility of the arrhythmia is the widely accepted endpoint of successful ablation of atrioventricular nodal reentrant tachycardia (AVNRT).C atheter ablation of the slow pathway has been accepted as a highly effective treatment, with low recurrence rates, for patients with atrioventricular nodal reentrant tachycardia (AVNRT).1 Complete elimination of the slow pathway is not necessary for long-term symptomatic relief of the arrhythmia; the most widely accepted endpoint for acute success of the procedure is noninducibility of the arrhythmia. 1,2Routinely after slow-pathway ablation, attempts at reinduction of arrhythmia are performed, with or without isoproterenol or other provocative medications. Some physicians use isoproterenol after ablation regardless of its use before ablation (strategy 1), [3][4][5][6][7] whereas others use isoproterenol after ablation of AVNRT only when it had been necessary for arrhythmia induction before ablation (strategy 2). [8][9][10][11][12] However, the published data available for the comparison of these 2 strategies are inadequate. 13,14 In any event, the effectiveness of arrhythmia reproducibility in evaluating the success of AVNRT ablation has not been well defined: AVNRT inducibility is not reproducible in more than one third of cases, 15 and that failure of inducibility after ablation might sometimes indicate the absence of reproducibility, rather than the success of ablation.To avoid the confounding effect of nonreproducibility, we designed this study to investigate whether the post-ablation administration of isoproterenol for reinduction of AVNRT (in patients in whom the original arrhythmia had been reproducibly inducible without the use of any provocative agent) has any effect on the long-term recurrence rate of the arrhythmia. In both strategies stated above, isoproterenolwhen necessary for arrhythmia induction before ablation-is also used to evaluate the inducibility of AVNRT after ablation. Therefore, we did not include in our study any patients who needed isoproterenol for initial induction of AVNRT.