Correlation of atrial electrocardiographic amplitude with radiofrequency energy required to ablate cavotricuspid isthmus-dependent atrial flutter

Objectives: The purpose of this study was to evaluate a possible correlation between atrial ECG amplitude in common atrial flutter (AFL) and radiofrequency (RF) energy required to achieve cavotricuspid isthmus block. Background: The amount of RF delivery required for ablation of typical AFL is variable. This variation has been attributed to the cavotricuspid isthmus anatomy. Atrial ECG amplitude can be a marker of atrial anatomic variations and therefore may correlate with RF duration required to achieve cavotricuspid isthmus block. Methods: Seventy consecutive patients were prospectively studied. Ablation of the cavotricuspid isthmus was performed by creating a line of block between the inferior tricuspid annulus and the inferior caval vein using 8-mm-tip electrode catheters. If more than 20 minutes of RF time was required to achieve conduction block, the catheter was changed to an irrigated-tip catheter. Atrial ECG amplitude was assessed in leads II, III, aVF, and aVL. Results: A total of 14 ± 11 minutes of RF energy was delivered to achieve block in all patients; 12 patients (8%) required more than 20 minutes. Atrial ECG amplitude showed highly significant correlations with cumulative RF energy (F and P waves in lead II: r = 0.703 and r = 0.737, P < .001). P-wave amplitude <0.2 mV and/or flutter wave amplitude <0.35 mV in lead II have a high negative predictive value to predict <20 min RF delivery (96% and 89% respectively). Conclusions: A significant correlation exists between atrial ECG amplitude and amount of RF required to ablate typical AFL. Atrial ECG amplitude may be a surrogate marker of characteristics of isthmus anatomy. These findings may influence the choice of catheter used for cavotricuspid isthmus ablation.