Evaluation of the surface ECG in detecting isthmus conduction block after ablation of typical atrial flutter

Abstract

Objectives: To investigate the value of changes in P wave morphology and duration detected by surface electrocardiogram(ECG) during proximal coronary sinus (PCS) and low lateral right atrial (LLRA) stimulation as amarker for complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation. Methods: Morphology, duration, and ratio of a positive terminal P wave were estimated in 52 typical atrial flutter patients before and after radiofrequency catheter ablation (RFCA). Results: Atrial flutter ablation resulted in a complete bidirectional isthmus block in all 52 patients. The terminal portion of the P wave towards a positive morphology was detected in 90.7% (47/52) patients both during PCS and LLRA stimulation. These changes were predominantly observed in the inferior leads. Positive morphological changes of the terminal P wave portion and the measured P wave ratio (40%± 12%) in the inferior leads indicating bidirectional isthmus conduction block with a sensitivity of 87.5% and a specificity of 91.7%were observed. An increment of 20 ms or more in P wave duration during the PCS stimulation and 10 ms ormore during the LLRA stimulation indicating the conduction block with a sensitivity of 90%and a specificity of 100%. Conclusions: The variation of P wavemorphology and duration in inferior leads of the surface ECG is a helpful technique to assess the complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation. © 2010 Wiley Periodicals, Inc.