Local electrogram-based criteria of cavotricuspid isthmus block

Double Potential Criteria of Isthmus Block. Introduction: The efficacy and outcome of cavotricuspid isthmus ablation guided by local electrogram-based criteria of linear block were prospectively assessed. Methods and Results: In 40-consecutive patients (age 65 +/- 11 years) with typical right atrial (RA) flutter (cycle length = 255 +/- 31msec), radiofre quency (RF) energy was delivered at electrograms in the isthmus coinciding with the center of the ECG plateau until termination of flutter, followed b y local assessment of isthmus conduction during slow rate low-lateral RA pa cing. 'Gaps' in the ablation line were located in the form of single or fra ctionated potentials centered on the isoelectric intervals of adjacent doub le potentials and ablated. Complete linear isthmus block was defined by the achievement of a complete corridor of parallel double potentials from the right ventricle to the inferior vena cava edge. Applications of 11 +/- 7 RF applications were required in ail patients to achieve a complete line of d ouble potentials separated by an isoelectric interval of 120 +/- 26 msec (r ange 60 to 190). After 6 +/- 3 RF applications, 6 (15%) patients had eviden ce of isthmus block using indirect RA activation sequence mapping without a complete line of double potentials. 5 +/- 5 further RF applications of eli minated local conduction and achieved complete linear block without alterin g descending septal RA activation. Conduction recovery occurred in 20 (50%) patients-1.85 times per patient-indicated by reversed changes in. local el ectrograms eliminated by further ablation of the recovered gaps. After disc harge, two recurrences (5%) occurred during a follow-up of 16 +/- 2 months. Conclusion: Double potential mapping is an effective assessment modality fo r local isthmus conduction. Slow conduction limited to the ablation line is observed during ablation in 15% of patients. (J Cardiovasc Electrophysiol, Vol. 10, pp. 662-669, May 1999).