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Aims Cavotricuspid isthmus conduction (CIC) is closely associated with the maintenance and recurrence of common atrial flutter (AFL). This study systematically sought to of acute CIC resumption than those without pacemakers (5/7 vs 29/117, P=0·007). The AFL recurrence rate was 4·8 % during a mean follow-up period of 218 months. Our results suggest that acute CIC resumption may be aIntroduction Radiofrequency ablation is a highly effective method of treating patients with common atrial flutter (AFL)[1–7]. Cavotricuspid isthmus conduction (CIC) is intimately related to the induction and maintenance of AFL, suggesting that bi-directional conduction block in the isthmus should be the aim of the ablation pro-cedure[8–18]. The recurrence rate of AFL was as high as 44 % if the noninducibility criterion was used as the endpoint for successful ablation[2]. It decreased to 9 % after bi-directional isthmus conduction block was employed as the criterion[8]. Several papers have reported that residual CIC, either slow conduction or unidirectional block, is associated with recurrence of AFL[9–11,19]. Schwartzman et al. observed intermittent block and recovery from conduction block[10]. Shah et al. also reported restoration of conduction immedi-ately after ablation[17]. Repeat electrophysiological studies in AFL patients have indicated a close rela-tionship between AFL recurrence and conduction recovery. However, the detailed properties of acute CI