Electrogram-guided radiofrequency catheter ablation of atrial tissue comparison with thermometry-guide ablation: comparison with thermometry-guide ablation.

Objectives: To characterize a new method for radiofrequency energy titration during ablation of atrial tissue based on reduction in electrogram amplitude. To compare this method with energy titration using electrode thermometry.

Background: Complications associated with "anatomy-based" atrial endocardial radiofrequency ablation for suppression of atrial fibrillation may be due to flawed methods of energy titration.

Methods: The effect of radiofrequency ablation on electrogram amplitude was characterized in a porcine model. A method for energy titration guided by electrogram amplitude reduction ("electrogram-guided") was developed and validated prospectively. Focal (smooth and trabeculated endocardial areas) and linear (smooth endocardial areas) ablation was performed comparing energy titration guided by amplitude reduction with electrode thermometry.

Results: Amplitude reduction during radiofrequency application was not necessarily equal among unipolar and bipolar electrograms in the ablation region; specific patterns of reduction could be discerned, based on factors such as catheter-endocardial orientation. A criterion of >90 % reduction of unipolar and/or bipolar amplitude best predicted pathologic lesion success. Electrogram-guided focal and linear lesions in smooth areas were free of lesion complications such as endocardial charring, barotrauma, or damage to contiguous extraatrial structures. However, there was a significant incidence of insufficient lesion size, principally non-transmurality, probably due to undertitration of energy. Thermometry-guided focal and linear lesions in smooth areas were uniformly transmural but frequently evidenced complications, due to overtitration of energy. Electrogram-guided focal lesions in trabeculated areas could usually not be achieved, probably due to insufficient contact of the ablation electrode with adjacent pectinate muscles. Thermometry-guided focal lesions in trabeculated areas were smaller than electrogram-guided lesions and did not evidence complications.

Conclusions: Electrogram-guided lesions in smooth endocardial areas were uncomplicated but had a significant incidence of non-transmurality. Thermometry-guided lesions were uniformly transmural but were frequently complicated.