Histological assessment of transmurality after repeated radiofrequency ablation of the left atrial wall

Abstract

Radiofrequency ablation (RFA) makes the Cox-Maze procedure less complicated but cannot always achieve transmural lesions. In this study, we assessed whether repeated application of RFA could improve histological transmurality even in thick lesions. Left atrial appendages (LAA) amputated from 20 consecutive patients (age 68 ± 9 years, 9 males) who underwent the Cox-Maze procedure using bipolar RFA devices were studied. Three different segments in the amputated LAA were ablated once, twice, or three times. Thereafter, cross sections made along each of the ablation lines were histologically assessed. Transmurality, which was defined as completion of transmural fibrotic changes, and wall thickness were investigated at an average of 3 different sites in each section. A total of 177 sites were investigated and divided into groups with single, double, and triple RFA treatments for 56, 61, and 60 lesions, respectively. Transmural lesions were observed in 25 (45 %), 27 (44 %), and 41 (68 %) lesions, respectively (P = 0.011). The transmurality was 100 % for all lesions with a thickness of 1.0 mm or less. In the thicker lesions (>1.0 mm), however, wall thickness impaired transmurality, though triple RFA was associated with significantly higher transmurality than single and double RFA (P = 0.005). Triple repetition of RFA was associated with higher transmurality of lesions than double RFA, especially for thicker lesions. Increasing the number of repetitions could improve the success rate of the Cox-Maze procedure using RFA devices.