Abstract: Objective To study the histopathological change in the radiofrequency cather ablation(RFCA) region adjacent to Coronary Sinus Ostium (CSO) and the correlation between the amount of energy and the size of jeopardized lesions after ablation. Methods Twenty Yorkshire pigs were randomized into control group and experimental group. Pigs of experimental group were ablated with 30W for different time and the control group was euthanasized as blank control.Observe the histopathol- oical change in the ablated region with light microscope, statistically analyzed the correlation between the amount of RFCA energy and the size of lesions. Results The ablation targes were localised lesions, there was no significant difference in area between 10S and 20S group when ablated with power of 30W(p>0.05). The injured area was significantly increased when the ablation time extended to 30s and more(p<0.05). The depth of RFCA lesions would be significantly deeper than that of 10s when the time extended to 20s and more(p<0.05), while the depth of RFCA lesions had no linear correlation with the amount of energy. Conclusions The injured size near CSO was significantly increased when the discharging time extended to 10S or 20S and the lesion area would correspendingly increase with the energy which ranged from 300J to 2400J.

Key words: coronary sinus ostium, atrioventricular node slow-pathway, radiofrequency catheter ablation, myo- cardium lesion, pig