Characteristics of atrial electrograms recorded in radiofrequency induced block lines in an experimental model

Aims. To analyze and quantify atrial electrogram modifications following th e induction of linear lesions in the atrial wall using radiofrequency ablat ion procedures. Methods. An epicardial multiple electrode (221 unipolar electrodes) was use d in 12 Langendorff perfused rabbit hearts to analyze atrial activation bef ore and after radiofrequency induction of a linear lesion in the left atria l wall. After confirming the existence of conduction blockade in the lesion zone by epicardial mapping and propagation vector analysis, six electrodes each were selected in the lesioned and non-lesioned zones in all experimen ts, comparing the amplitude, maximum negative slope and morphology of the e lectrograms in both zones, before (control) and after radiofrequency delive ry. Results. Analysis of the reproducibility of the measurements in two consecu tive cycles showed a variation of 1 +/- 5% for amplitude (NS) and 1 +/- 9% for maximum negative slope (NS). In the non-damaged zone, amplitude (105 +/ - 22%) and slope (92 +/- 16%) (values normalized with respect to those reco rded before radiofrequency) did not vary significantly following radiofrequ ency, and simple electrograms were the most frequent recordings (82 vs 83% in control; NS). Amplitude (19 +/- 7%, p < 0.001) and slope (24 +/- 11%; p < 0.001) decreased significantly in the lesion zone, as did the percentage of simple electrograms (6 vs 86% in control; p < 0.001). In this same zone the morphology could not be determined in 12% or the recordings, while mult iple electrograms were obtained in 15% (vs 2% in control; p < 0.01), and th e most frequent type corresponded to double electrograms (67 vs 12% in cont rol, p < 0.001), with both components coinciding in time with atrial activa tion in the zones proximal and distal to the lesion line. Conclusions. Electrograms recorded directly in radiofrequency induce block lines show a significant decrease in amplitude and maximum negative slope. Double electrograms predominate in these recordings, both components of whi ch represent activation on either side of the lesion. In a small proportion of cases simple and multiple electrograms can also be recorded in the bloc k line.