Clinical significance of residual slow cavotricuspid isthmus conduction after ablation of typical atrial flutter

The purpose of this study was to evaluate the clinical significance of resi dual slow cavotricuspid isthmus (IT) conduction on the ablation line after typical atrial flutter (AF) ablation, undetected by analysis of right atria l (RA) activation. Seventy patients with AF underwent IT ablation. In the f irst 35 patients (group I), IT block was verified only by the RA activation sequence. In the subsequent 35 patients (group II), IT block was verified by the presence of parallel double potentials with an isoelectric interval through the entire ablation line (in addition to RA activation sequence cri teria) during pacing from the low lateral RA and the coronary sinus ostium. In group I patients, residual IT conduction was retrospectively analyzed a t the ablation site immediately after the last radiofrequency (RF) applicat ion. Six of 33 group I patients (18%) with IT block had residual TT conduct ion represented by fractionated or multicomponent potentials immediately af ter the final RF application. Four of these 6 patients (67%) had recurrence s of AF, 3 +/- 1.4 months after ablation. Four (12%) of 33 group II patient s with IT block had residual IT conduction in the ablation line after creat ion of IT block confirmed by RA activation sequence. This conduction was el iminated by 1.6 +/- 0.9 further RF applications in all 4 patients. No AF re currence was observed in group II patients. Up to 18% of patients with appa rent IT ablation had residual slow IT conduction on the ablation line. This conduction was associated with AF recurrences and must be eliminated to ac hieve complete cure of AF.