Evaluation of the Ablation Effect Related with the Initial Impedance and Impedance Drop in Atrial Fibrillation Ablation

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Background: Impedance is used one of the index to evaluate the effectiveness of radiofrequency ablation. It is often known that the 10 ohm drop of impedance is a index for effective ablation. But decrement of the amplitude of electrogram is not always reflected by the impedance 10 ohm drop. Therefore we examined the relationship between the impedance and the amplitude decrement of the ablation. Methods: Consecutive 40 patient with atrial fibrillation was enrolled in this study. They were divided into three groups. Low group (<90 ohm), Medium group (90–140 ohm), and High group (140 ohm>). Which was based on the mean and standard deviation of the start impedance. We compared the time for 10 ohm drop and degree of the decrement of the amplitude in that time from start impedance. Results: The amplitude decrement was 62.6±23.8% in Low group, 48.8±24.2% in Medium group, 36.1±20.6% in High group. The High group significantly had lower degree of the decrement than that of other groups. The 10 ohm drop time was 25.7±13.5 sec in Low group, 14.6±8.6 sec in Medium group and 10.6±7.6 sec in High group. Conclusions: An impedance 10 ohm drop might not be useful for effective ablation for those who have higher initial impedance.